MPC Logo

MPC Field Day Report – Insect Management

More than 110 growers attended the August 2014 field day at Eric and Mark Balmer’s farm.
The focus was on insect management, specifically lacebug and sigastus weevil and the use of spreaders and wetters in pest and disease management.

Key points from the day were:

  • Sigastus Weevil is a new pest that has been found in the Northern Rivers Region;
    Effective control of Sigastus Weevil requires an integrated approach using insecticides and cultural (mulching infested nuts) control;
  • The selection of insecticide for Sigastus Weevil control needs to be considered in the context of an IPM program. If one insecticide is continually used, it could create other pest problems such as thrips and mites;
  • Changes by the Australian Pesticides and Veterinary Medicines Authority (APVMA) to label and application requirements means larger droplets will need to be produced from an airblast sprayer to avoid drift. When larger droplets are used, it is not possible to rely upon droplet number to achieve coverage. You must ensure your sprayer is ‘hitting the target’ (nut);
  • Once you hit the target with a droplet, there are new spray adjuvants available that assist in getting that droplet to cover the target (nut);
  • You can check your sprayer coverage simply by adding a ‘dye’ type product (eg Screen) to water and applying it. After a few minutes it will dry and you can see where the spray has gone;
  • Anyone who wants to check their sprayers coverage can contact Jim Patch at MPC who can supply the dye and assist with carrying out the coverage check.

Sigastus Weevil Research

Craig Maddox, NSW DPI

Craig outlined the research NSW DPI has undertaken on Sigastus Weevil. They found Sigastus Weevils are long lived. In an experiment to understand the lifecycle of the pest, female Sigastus Weevils live on average for 68 days (just under 10 weeks) but can live for up to 156 days (just over 22 weeks). One female can lay between 10 to 40 eggs per week, but egg laying will only happen if the nuts do not have hardened shells in them. Generally the female only lays one egg per nut, and chews through the stalk of the nut, which causes the nut to drop to the orchard floor. The female will sometimes only chew partway through the stalk, with the nut dying and hanging in the tree. Generally it takes 40 days from egg laying to emergence of the weevil from a nut. This is a fairly long cycle, making a multi pronged management strategy critical for the control of the pest. For macadamias, Sigastus weevil will only lay its eggs into the husk of nuts that are pre-shell hardening.

Sigastus Weevil feeding and egg laying site. Note the triangular shape mark, indicating an egg laying site. Photo Courtesy Craig Maddox, NSW DPI

Sigastus Weevil feeding and egg laying site. Note the triangular shape mark, indicating an egg laying site. Photo Courtesy Craig Maddox, NSW DPI

Being long lived Sigastus weevil spends the rest of the time in the orchard feeding on leaves and bark – waiting for the next crop to commence so they can begin breeding. If out of season flowering and nutset occurs, the weevil will breed. If out of season flowering and nutset doesn’t occur, it assists with control as there is only one opportunity per year for the weevils to breed.

Sigastus Weevil feeding on macadamias. Photo courtesy Craig Maddox, NSW DPI

Sigastus Weevil feeding on macadamias. Photo courtesy Craig Maddox, NSW DPI

Crop loss

In a trial at Clunes, it was found that up to 30% of the crop can be lost from sigastus weevil damage. This trial was on a farm where spraying had been undertaken to control the insect.

Monitoring

From research and pest consultant feedback, it has been found there are different monitoring tools available. These include:

Collecting nuts from the ground and checking for signs of sigastus weevil damage. When a female lays an egg in a nut she will scarify the husk in a triangular shape, inserting the egg deep into the husk, normally on the edge of the husk and developing nut layer. When the shell has hardened, the female will not lay eggs in the nut, but will continue to feed on the husk. The damage at this time will be seen as a ‘half spherical crater’.
Cutting open nuts – when you cut open a nut that has been fed on and had an egg layed in it, you will find the larvae inside the developing nut or damage and/or an egg in the bottom of the husk layer (against where the developing nut would sit).

Sticky traps – in a trial on other insect pests, sigastus weevils were found on sticky traps. Sticky traps haven’t been used as a tool for monitoring sigastus weevil on a large scale, but they may be a useful tool in providing some information on the insects activity.

Sigastus Weevil Larvae and damage inside a developing nutlet. Photo Courtesy Craig Maddox, NSW DPI.

Chemical screening

Craig emphasised their screening of insecticides for the control of sigastus weevil is only in the early stages and needs further testing. One critical aspect found in their testing is that direct contact of an insecticide will only result in low levels of control (around 40%).
What they did find however is that feeding for several days on nuts that have been sprayed with insecticide will provide good levels of control. This means that good coverage is essential for the control of sigastus weevil. Craig emphasised based on early testing results, life cycle analysis and the experience of growers in the Atherton tablelands area (where this pest originates from), chemical applications alone will not provide adequate control. You also need cultural control to get good control. Cultural control options include mulching sigastus damaged nuts and sweeping out and harvesting. The control of sigastus weevil needs to be considered in the overall insect management program – IPM. Craig showed results from a trial on variety A16 examinig thrip and mite damage on new flush. Although only the first seasons data, the results showed that the over use of Beta Cyfluthrin (Bulldock) can increase the thrip and mite problem. The key point Craig emphasised is that it is critical to rotate your insecticides to avoid creating an insect problem you could have avoided. He suggested that you only use 2 Beta Cyflthrin sprays in a season and if you need another insect spray (especially during spring) an alternative to use is Acephate (Lancer).

Biological control of Sigastus Weevil

As reported in the May edition of The Nutshell, NSW DPI has isolated a fungus that kills sigastus weevils. The fungus, Beauvaria bassiana is effective against a range of beetle species, but requires humid weather to survive. Craig highlighted that fungicides applied to control husk spot will also kill the Beauvaria fungus, so an integrated approach to pest and disease management will be needed. This research work is in its early stages, but it is showing there is a fungus that attacks sigastus weevil with potential to use it as part of the overall management system to control and limit nut loss.


Sigastus Weevil Experiences

Mark Balmer, Burrawong Orchard
Mark Balmer and his father Eric own and manage Burrawong, a 20ha Macadamia farm at Clunes. For the past two years they have dealt with sigastus weevil and Mark has developed an extensive knowledge of the pest, sharing it with growers at the field day. Mark found the best time to look for sigastus weevil is late afternoon as this is when they are most active. Most damage was found on the edges of the orchard. Mark found most nuts fall to the ground after being fed on and having an egg layed in them, but not all nuts fall.
Sometimes the female has only partly chewed through the stalk and it hangs in the tree. As the egg and larvae in the nut are protected from any insecticide application, Mark has found that mulching is a critical part of the management program. He initially tried blowing small nutlets out from the tree row, but this hasn’t been effective as the nuts won’t roll if they get caught by something such an exposed tree root or large stick.

He then tried sweeping the nuts out of the tree row with the sweeper on his toro harvester. He found this was successful as it moved all the nuts out from the tree row to where he could mulch them up. With his mulcher, Mark found that worn hammers were not very effective at smashing up the small nutlets (eg pea sized) so he replaced them and then found he got good results. The new hammers meant the nutlets were smashed into very small pieces. “Although mulching is slow and uses a fair amount of diesel, just relying on chemical control wouldn’t be effective as we would still get continual emergence of new weevils”, said Mark. Mark has collected lots of samples in jars to observe the sigastus weevils. As part of this work he has been placing sigastus weevils into jars with ones that are infected with beauvaria fungus.

After a few days, he has then released them back into the orchard, as they are then infected with the fungus. “As the humidity increased I found the rate of death increased rapidly. Initially I would put them in the jar and after about a week they would be starting to show signs of infection. Then as the humidity increased within about 2-3 days I would see signs. I was a bit sceptical about the whole thing but thought it would be worth a try. When I found a dead sigastus weevil with fungus growing out of it over 600m from where I was releasing them, I thought this might be useful.”

During winter Mark still found sigastus weevils in groups and not moving around. “I think they don’t like the cold weather. They are trying to survive the cold by not moving around a lot and keeping themselves dry. They can’t reproduce and so are just waiting for the next lot of nuts to come so they can breed”. Mark has found weevils are strongly attached to the nut, branch or leaf they are on. “I found them on a branch the other day. I cut the branch off and took it on the motor bike back to the office. When I got back they were still on the branch – they hadn’t moved”. Mark found that although sigastus weevil can fly they tend to move around the orchard by walking. The only time he has seen them flying is on a hot day with a strong wind blowing.

Mark said sigastus weevil did not appear to have any preference for particular macadamia varieties “but attacked varieties planted on the orchard boundary first. In my case these varieties are A4, 344,H2 and Nutty Glen.” He estimates his crop loss was about 12% from Sigastus weevil. “It is really hard to estimate how much I lost as it was worse in some areas than others. From what I saw, I think it was about 10t I lost. That 10t would have been worth over $30,000 and so there is no doubt this is a serious pest for me”. Mark believes it will take a combination of control measures to control the weevil. “I don’t think chemical control alone will work. From what I have learnt and done, I believe ground control is really important. If you just spray and don’t smash the nuts up that the weevils are in on the ground, they will just keep breeding”.

Spray Adjuvants—what are they and where do they fit?

Matt Moyle, Nufarm Australia

Matt spoke about the spray adjuvants available and the changes the APVMA are introducing for drift management.

Adjuvants fall into the following broad range of categories:

  • Non-ionic wetters (spreaders);
  • Oils (spreaders with insecticidal activity);
  • Rainfastening agents (stickers);
  • Silicon based (Super Spreaders)
  • Buffers (Acidifiers).

Each category has a fit within a pest and disease management program.

Non-ionic wetters (spreaders)

Non-ionic wetters work by breaking the surface tension, which causes a droplet to spread. They do not generally provide penetration into the plants tissue, only spreading the spray. They can increase drift of sprays and cause spray mixtures to foam heavily.

The effect of a spray adjuvant on the amount of drift generated from a nozzle. Note how some non-ionic wetters increase the amount of drift (eg Chemwet) while others can reduce drift (eg Activator).

Oils

Spray oils are a good spreader to use at times as they have insecticidal activity. They work by smothering pests, making them useful against small insects such as leaf miner and scale. When used in a spray mixture for their insecticidal properties, oils are cost effective, but if they are added just as a spreader, they are not very cost effective. Oils are excellent in aiding drift reduction.
When oils are used at low rates they can have compatibility issues with Spin Flo and some copper based products. When using oils with these products you often need to add extra wetter to help keep the products in solution.

Rainfastening agents

As their name suggests, rainfastening agents are designed to protect pesticides from being washed off by rain. Examples of rain fastening agents are Bond, Nu-Film and Designer.

Why is rainfastness important?

Rain fastening agents either contain latex type compounds or are made from natural substances such as pinene (pine resin). They work by forming a “stocking” over pesticides, which prevents washing off. They allow normal breakdown processes of the pesticide to occur (except Nufilm at very high rates). If Nu-film is used at a very high rate, the with-holding period may not be as stated on the label. Nu-film also requires two hours of sunlight to “activate“, to achieve full rainfastness.

Silicon Based (Super Spreaders)

These products assist with penetration into the leaf surface and achieve improved coverage. When selecting a penetrant, you must be careful to ensure you are using it for the job it was designed for. For example, Pulse was designed to assist with woody weed control and is very effective at breaking down the waxy cuticle, to assist the product enter the plant leaf. If used when applying a foliar spray, it can cause burning of the leaf. Pulse is however very effective at assisting the uptake of any chemicals applied to the trunk of a tree.
Du-wett is a super spreader. It breaks the surface tension of the spray droplet and spreads the droplets over the leaf or nutlet. It has excellent crop safety – it won’t cause leaf burning problems if used correctly. Designer is a combination product – it is like a mix of a Bond like product (rainfastner) and Du-wett (super spreader). It has a low drift level and is low foaming. This product is very usefull in assisting with the spread of chemicals, especially when using large droplets.

Acidifiers and Buffers

As the name suggests, these products can either acidify the tank mixture or buffer it. This is extremely important when using pesticides that suffer alkaline hydrolysis. LI700 acidifies spray tank mixtures and is extremely important to use when applying Lepidex. LI700 has a low drift rating, can increase the uptake of foliar fertilisers and is often used with herbicides to improve the effectiveness.
Another effective product is Agri-Buffer, which changes colour when the pH goes below 7. A pH of less than 7 will generally negate problems of alkaline hydrolysis and a product like Agri-buffer makes it easy to see if your spray tank mixture is at the correct pH.

Warning – copper can burn foliage when acidified too low and copper can fall out of solution. It is recommended that when using an acidifying agent not to add copper based products to the spray tank.

Du-Wett

Du-Wett is an organosilicone based super-spreader designed specifically for the application of crop protection products to horticultural and arable crops. Du-Wett is a blend of organosilicone and other organic fluids, formulated to not only give super-spreading properties on plant foliage, but also to improve retention and deposition of spray droplets on all plant surfaces. Du-wett Spreads eight times better than non-ionic wetters. Due to the strong spreading ability of Du-wett, it is critical to use at the correct rate. It does however foam strongly in tank mixes. If it is used with very fine droplets it can increase drift.

What rate do I use?
It’s best to trial Du-Wett before using it for spray applications. It is recommended you start at 75ml/1000L (Dilute volumes) and assess the coverage/spread achieved. If you are using a concentrated spray volume (eg 2X). Start at 150ml/1000L for 2X. The best way to assess coverage is to use a product like Surround or Screen as a ‘visual indicator’. By adding one of these products when testing, you can quickly see if coverage has been achieved. Matt suggested to spray with only water, Du- Wett and Screen on half a row and then assess the coverage (get off the tractor!). If spray is running off the leaf and onto the ground (compared to a normal spray) then you reduce the Du-Wett rate by 30% and re-assess. If you do your first trial and the spray application isn’t at the point of run-off, i.e. droplets have not joined together into a single even sheen, then you should increase the Du-Wett rate by 30%.

The spray coverage achieved on macadamia leaves without and with Du-Wett. Note same water volume per tree used.

Designer

Designer is a blend of an organosilicone super-spreader and a latex polymer. This combination gives the product unique properties:

  • Super-spreading ability over three times greater than conventional nonionic spreaders
  • Improved deposition of droplets due to unique “anti-bounce” chemistry which absorbs energy when a droplet hits the surface

Designer does not encapsulate pesticides so will not lock up active ingredients nor slow them down, nor will it increase residues. Good rainfastness improves adhesion of chemicals dramatically in wet weather. It is rainfast as soon as it dries. Matt Suggested just like Du-Wett, trial some Designer on an area and assess its effectiveness. He suggested starting at 150ml/1000L (Dilute volumes) or 300ml/1000L for concentrate (2X) sprayer setups. Or more simply, Designer is double your Du-Wett rate.

NEW APVMA Regulations

The Australian Pesticides and Veterinary Medicines Authority (APVMA) implemented new policy on 1 March 2010 that requires all new pesticides to be assessed for the potential risk of spray drift. The labels of currently registered pesticides are being reviewed to include comprehensive instructions for managing spray drift. Label statements of new products will include information on factors such as:

  • Droplet size
  • Weather conditions
  • No spray zones
  • Record keeping requirements

These changes are significant. You must read and understand these new statements before using any product which has been through the process. Older chemistry products that haven’t had their label changed in recent years currently do not have the new drift restraints on the label (e.g. Lepidex, Lancer…) but the changes will come!. An example of these new requirements is the Cabrio Label:

Other information that is contained on new labels includes the droplet sizes to be used.
With the new label requirements, Matt indicated that larger droplet sizes will be the normal on labels and it will be essential to use these to meet the label requirements.
As larger droplets will now be used and you will have fewer droplets being produced by your sprayer, it is critical to ensure your sprayer is setup to achieve good coverage (droplets hit the target—developing macadamia nuts).
Once your droplet is there, the new adjuvants like Designer have the ability to take over and complete the coverage process by distributing the droplet across the surface of the nut.

Definition of the different droplet sizes produced by airblast sprayers. Note coarse droplets size is 308-459µm (0.3mm—0.4mm) and will need to be produced under the changes introduced by the APVMA

Definition of the different droplet sizes produced by airblast sprayers. Note coarse droplets size is 308-459µm (0.3mm—0.4mm) and will need to be produced under the changes introduced by the APVMA

Why is coverage so important?

Matt outlined that coverage is crucial because most of the pesticides products used in macadamia crops are non systemic protectants. This means they have very little movement into the plant and so rely upon coverage of the (nut) surface to provide control.

Pesticide performance can be influenced by how they behave on a plant—whether they stay on the surface or enter the plant. Note that most commonly used macadamia pesticides are non systemic protectants and so stay where they are applied. This makes coverage crucial to get the best results from them.

Pesticide performance can be influenced by how they behave on a plant—whether they stay on the surface or enter the plant. Note that most commonly used macadamia pesticides are non systemic protectants and so stay where they are applied. This makes coverage crucial to get the best results from them.

Sigastus Weevil

Sigastus Weevil was initially found infesting macadamia orchards on the Atherton Tablelands in Far North Queensland in 1994/5. Fay et al in their preliminary report Sigastus Weevil – An Emerging Pest Of Macadamias in North Queensland (QDPI) stated that nuts may be attacked until shell hardening stage, and that larvae consumed whole kernel with larval duration being shorter in larger nuts. They went on to say that crop loss in an unsprayed orchard may be up to 30%.

It was noted the weevils were susceptible to Methidathion (Supracide®/Suprathion®) and Carbaryl (Nufarm Flowable Carbaryl 500 Insecticide®) applied as a control measure for Fruit Spotting Bug/Nut Borer. It was also noted that Beta- Cyfluthrin (Bulldock®25 EC) was less effective than other chemicals and took longer to control weevils. It was recommended that fallen nuts be swept into a windrow and mulched to provide a mechanical control for the larvae/eggs in the nuts in the September to December period.

Sigastus Weevils have been detected in the Clunes/Eureeka area for the past four years. In the 2014 growing season they were found across the Northern Rivers in isolated pockets. The reason for this expansion in territory is unknown. Some growers suggest it may result from the major storm event in January 2013 – with wind moving them around and the out of season flowering resulting from this event, giving the weevils access to a breeding source all year round.
Growers in the Clunes/Eureeka area whose orchards were affected by weevils have used a combination of insecticide applications (in conjunction with their Fruit Spotting Bug/Nut Borer control) and mulching of fallen nuts. There is variability in the success of the chemical control measures used and it is apparent timing and coverage is critical for success.

The winter of 2013 was very mild which produced multiple flowerings in the Northern NSW growing area. There were at least three distinct flower sets for the 2014 macadamia crop – which provided a constant supply of developing nutlets for the Sigastus Weevils to lay eggs in and feed on. Nutlets from about a 5 cent size were seen to have been attacked, with larvae inside.

Sigastus weevil on a macadamia nut showing scarified areas in the husk from weevil feeding (source NSW DPI)

The female weevil scarifies an area on the husk as shown in Fig 2. through which it inserts its ovipositor into the husk (above the unformed shell) or onto the surface of the developing kernel. After an egg is deposited, the female weevil chews into the nut stork and this usually causes the nut to fall from the tree about three days later. In some cases the nut doesn’t fall.

 

Fig 3. Sigastus larvae in husk/shell.

The egg hatches within the developing nut and the larvae proceeds to consume the kernel before emerging up to six weeks later as a fully developed weevil. The weevil then flies off into the orchard to recommence the cycle. Once shells of macadamia nuts harden the female weevil stops laying eggs into nuts as it is unable to penetrate the hard shell. They do however continue to feed on the husk of nuts. Although not fully understood, it is believed adult weevils live for many months. The difficulty with managing the weevil is little is known about it’s lifecycle. We seem to have continual feeding and egg laying which causes multiple generations to be present at the same time. Added to this the eggs are laid in the husk and the developing weevil larvae are protected by the husk. This makes the timing of insecticide applications difficult. With these difficulties in mind, MPC has been working with the NSW DPI Entomology team for alternative control options. This has involved a small pilot project with an affected MPC grower to ascertain if the Sigastus Weevil is susceptible to a naturally occurring fungus known to attack insects and to see if this can be used to give population control. All work in this pilot project is through the contribution of time and effort by the grower, MPC staff and NSW DPI.

This project is not funded by Horticulture Australia Limited (HAL) or the Australian Macadamia Society.


Growers story on his orchard Sigastus Weevil experience

Mark Bulmer

Mark and his father Eric operate a family owned orchard in the Clunes area of NSW. They have seen an increase in the population of Sigastus Weevils in their orchard during the past two seasons, with a significant increase running up to the 2013 season.

“It appears that A4 is particularly attractive to Sigastus Weevil in our orchard as it has had almost continual flowering and nut set cycles for the past two or three seasons. There are always nuts for the Sigastus Weevil to lay eggs into. We were keen to get control of this insect pest as its numbers were increasing particularly in 2013 and we were concerned by the damage levels. We applied sprays of Carbaryl, Suprathion and Acephate to control Fruit Spotting bugs/Nut Borer last season hoping we would also control this weevil. We swept nuts into wind rows and mulched them on a regular basis hoping to achieve control by mechanical means.

Unfortunately all these approaches didn’t work as we had hoped and we didn’t appear to get any real control until shell hardening, when the pressure eased off”, Mark said.

“When all the varieties we have set nuts in January 2014, during the drought, we noticed once again we had significant numbers of active Sigastus Weevils”, Mark said.

Through consultation with MPC, Mark collected 100 Sigastus Weevils in March 2014 and these were provided to NSW DPI. These weevils were sprayed with a naturally occurring fungus that is known to attack insects and placed in cages in the field to see what happens. After seven days it was noticed they had died and the weevils had the fungus growing out of them. A number of these dead Siguastus Weevils were then placed in containers with fresh live ones, so a new batch of weevils could be infected. As these weevils showed symptoms of infection, they were then released into the orchard. The aim being that if they were infected, they would come into contact with other weevils and spread the fungus.
Craig Maddox from NSW DPI said: “the fungus requires moist, humid conditions to work. So we waited until we had the right weather conditions before we commenced this trial”.

Mark Balmer said: “Half the collected specimens were returned to the orchard just after they were inoculated with a fungus. The first samples of weevils were watched for signs of them dying for seven days before I saw any effect. It started raining on day five and by day seven, seven had died. The increase in humidity appeared to trigger the growth of the fungus. It is easy to see the white fungus growing out of the insect’s body. The remaining infected Sigastus Weevils were released, three cadavers were pinned to trees and four were retained for further inoculation of future collected specimens. Several days later a Sigastus Weevil was found dead and covered with white fungus several hundred metres from the release site.

“A second release of weevils occurred in early April during a showery period; however this lot started to die within four days of being inoculated”.
Craig Maddox from NSW DPI said,: “The catch, inoculate and release of the weevils is just a start to be sure the fungus used is effective in killing the weevils. If it continues to show promise, we will look at a larger scale field trial to see if it gives results”. A blend of commercially available fungus with fungus of the same species used in the initial trial may be used in the orchard to test for control of Sigastus Weevils in the future.

Mark has also made many other observations of Sigatus Weevil. “The weevils have an interesting habit of hiding or rolling up and dropping off the trees when I approach the trees they are in. They also appear to be strong flyers,” Mark said.

Mark has also undertaken some of his own research. “I did a trial in my refrigerator at home to try to simulate a cold winter night to see if the weevils would be adversely affected by the cold. The weevils were placed in the refrigerator at 1ºC for 11 hours over night. I took them out in the morning and placed them out side in the open. They were all pretty sluggish to start with but by 10.00am when the temperature was about 22ºC they were once again looking pretty lively. So from my observation it might take more than a cold winter to stop these things!” Mark said.

It is very early days but the results from the research into the use of pathogenic fungi looks promising. The fungus used in this research is potentially a risk to anyone who is Immuno compromised, so precaution must be taken with its use – and the appropriate PPE must be worn.

Spotting Bugs In Macadamias

Article by: Kevin Quinlan, Supply Chain Manager – NIS, MPC, Craig Maddox I&I NSW, Centre for Tropical Horticulture.
Ruth Huwer I&I NSW, Centre for Tropical Horticulture.

This article provides a brief overview of the management of spotting bugs (Amblypelta spp.) in macadamias, including the identification of the pest, the types of damage caused and the control strategies used.

Key points are:

  • adult spotting bugs can feed on fully mature nuts, as they secrete enzymes when feeding that allows them to penetrate the shell;
  • late season damage often does not show up on macadamia shell, but the kernel has been damaged. This late season damage is often called “blind stings”;
  • a good monitoring program is critical allowing you to determine when there is activity occurring in your orchard and apply control strategies as needed;
  • spotting bugs will continue to feed in an orchard until there isn’t any food available or a more appealing food source emerges;
  • you only need small numbers of spotting bugs to have significant amounts of damage;
  • the aim of a spotting bug management program is to reduce the population early in the season, so numbers do not build later in the season.

Introduction

Spotting Bug is the general name used to describe the fruit-spotting bug (Amblypelta nitida) and the banana-spotting bug (A. lutescens lutescens). Both of these insects attack a wide variety of horticultural crops, including avocado, custard apples, lychee, mango, passionfruit and pecans, as well as many native and ornamental fruit and nuts. Spotting bugs are not the only bug species that attack macadamia but they are the most perennial problem in all growing areas.

Spotting Bug feeding on Murraya paniculata berries NSW (courtesy I&I NSW)

Spotting Bug feeding on Murraya paniculata berries NSW (courtesy I&I NSW)

What do they look like?

Adult spotting bugs are yellow-green-brown in colour and about 15mm long. There are 5 nymph stages (called instars), with the early stages being ant-like, orange-brown in colour and with prominent antennae. Later stages are greener in colour and have wing buds. A distinctive feature of the nymphs is that the second last joint of the antenna is black and flattened. It is rare to see spotting bugs in trees, as both adults and nymphs are very alert and if they fear being seen they will hide behind fruit or leaves. They also have the ability to drop down to the ground quickly to avoid being found.

Life cycle stages of fruit spotting bug nymphs and adults. From Macadamia problem solver and bug identifier © The State of Queensland, (2003)

Life cycle stages of fruit spotting bug nymphs and adults. From Macadamia problem solver and bug identifier © The State of Queensland, (2003)

banana-spotting-bug-nymph

Banana spotting bug nymph. From Macadamia problem solver and bug identifier © The State of Queensland, (2003)

When are they present?

Most damage to macadamias occurs between September and February, with some of the thinner shelled and later varieties being attacked all year if spotting bug is left unmanaged. Spotting bugs are able to penetrate fully hardened shells due to the long stylet (microfine syringe like feeding tube) and powerful enzymes they release while feeding. This late damage can show up as a ‘blind sting’, as you can not see the damage on the outside of the shell but the kernel is damaged. Blind stings are difficult for growers and processors to detect until after the shell is cracked.

Research by Industry and Investment NSW (I&I NSW) at the Centre for Tropical Horticulture (CTH) Alstonville, over several seasons and on several crops, has been able to link chemicals in flowers with movement of female fruit spotting bugs. These chemicals are known as “semio-chemicals or karimones” and they signal to the adult bug populations that the macadamias are about to develop nutlets. This is very important as the semio-chemcials allow the spotting bugs to know that if they now enter a macadamia orchard and lay eggs, food for their developing nymphs will be plentiful.

Eggs have been collected in spring from the flowers of many crops, including mango, lychee, and avocado but none more than macadamia.As very few eggs are laid, a small number of spotting bugs can do considerable damage. This makes an effective monitoring program a crucial part of spotting bug management.

Eggs of fruit spotting bug laid on early stage macadamia florets August/September 2009 at CTH Alstonville (courtesy I&I NSW)

Eggs of fruit spotting bug laid on early stage macadamia florets August/September 2009 at CTH Alstonville (courtesy I&I NSW)

Typical fruit spotting bug cycle for macadamias. Note the months indicated for a particular active can vary depending upon seasonal weather conditions and crop growth stages.

Typical fruit spotting bug cycle for macadamias. Note the months indicated for a particular active can vary depending upon seasonal weather conditions and crop growth stages.

There are two to three generations of spotting bug during the macadamia nut development. The first egg laying usually occurs in August/September and the second in October/November, with it taking approximately 42 days for a spotting bug to develop from an egg to an adult.

Once an adult, spotting bugs can live for up to six months. During the main summer period the adult bugs are far more mobile in the orchard and can invade and leave areas quickly. As a few spotting bugs can do considerable damage, this makes breaking their breeding and feeding cycles crucial.

Normally two applications of a registered insecticide 4 weeks apart during the spring build up and one just prior to Christmas removes the threat for the older Hawaiian varieties. However when poor nutset occurs in the September flowering we often get a season with summer and/or autumn flowering (like 2010) which can immediately start another cycle for the spotting bug. This virtually keeps them in the macadamia orchard all year resulting in higher damage.

Once adult spotting bugs enter your orchard (or are bred in your orchard) they will not move onto another crop until the food source dries up (i.e. nuts start to fall at harvest) or they find an alternative food source that is more attractive.
If your early season management stops the nymphs from maturing and the adults from reproducing and feeding, you will reduce the potential for late season damage, which is very difficult to see or remove from your nut in shell (NIS). Good monitoring is crucial to ensure you detect any populations of spotting bug and so apply control strategies only when necessary.

What does the damage look like?

Damage caused by fruitspotting bug depends upon the stage of development of the nuts. I&I NSW carried out a series of experiments between 1997- 2005 at CTH Alstonville, where they caged macadamia nut racemes for an entire season. Fruit spotting bugs were released into the cages at different stages of the season, to ensure nut damage.

This series of experiments showed that all early season damaged nutlets basically dropped from the raceme up to November. After this time nuts continued to be damaged but less and less fell off the tree. The visible symptoms of damage follow this same pattern, with less and less damage obvious until late in the season spotting bug damage is only visible in the kernel. There are also occasions where small nymphs feed only on the husks. The following photos show the damage caused at different stages of development.

Typical fruit spotting bug damage symptoms

All images below are form Macadamia problem solver and bug identifier© The State of Queensland, (2003)

Spots on a young nut.

Spots on a young nut.

Sectioned nut showing lesions on the inside of the husk (nut removed)

Sectioned nut showing lesions on the inside of the husk (nut removed)

Sectioned developing nut showing damage to soft shell and developing kernel

Sectioned developing nut showing damage to soft shell and developing kernel

Shell damage

Shell damage

Kernel Damage

Kernel Damage

 

Can spotting bugs feed on fully mature nuts?

Unfortunately yes. Due to the long proboscis (feeding tube) that fruit spotting bugs have and the secretions they exude from it, they can penetrate fully mature nuts. In some orchards they attack late in the season (January to early February) and damage the kernel.

Caged racemes from 344 and A16 trees with fruit spotting bug introduced for a weeks feeding during the month labeled. January feeding on both varieties left dark welts in the forming shell, March feeding still visible in the kernel but not on the shell. (courtesy I&I NSW).

Caged racemes from 344 and A16 trees with fruit spotting bug introduced for a weeks feeding during the month labeled. January feeding on both varieties left dark welts in the forming shell, March feeding still visible in the kernel but not on the shell. (courtesy I&I NSW).

The damage does not show up on the outside of the shell, but the kernel is damaged. This makes it difficult to remove these damaged nuts on a sorting table. (

Green vegetable bug (Nezara viridula) is also able to feed on mature nuts, although it will not usually breed in the crop (like fruitspotting bug). Green vegetable bug has even been found to feed on dropped nut if left unmanaged. Green vegetable bug invade from pasture legumes, soybean or passionfruit crops and also have many weed hosts (especially black berry nightshade). It is much easier to control if the weed management is good on your farm. This damage also does not show up on the outside of the shell.

Both types of bugs have the potential to make significant proportions of the crop worthless quickly, and as a result, careful monitoring is required to determine if late season bug activity is present in your orchard so that appropriate control strategies can be carried out.

Fruit spotting bug feeding directly through the shell to create a blind sting (left) (courtesy I&I NSW). and the typical blind sting damage found in macadamias (right). Note the absence of damage on the shell (courtesy MPC).

Fruit spotting bug feeding directly through the shell to create a blind sting (left) (courtesy I&I NSW). and the typical blind sting damage found in macadamias (right). Note the absence of damage on the shell (courtesy MPC).

Are there variety preferences?

Research at CTH Alstonville has found that there are varietal differences in the levels of fruit spotting bug damage found. Generally, thinner shelled varieties have been found to suffer higher levels of damage than thicker shelled varieties. This means that you’re monitoring and control strategies may need to be different for particular varieties, especially late in the season. In thin shelled varieties, if spotting bug is not controlled, crop losses over 80% per tree are not uncommon, with an average of around 30-50% being observed most years.

Monitoring and action levels

A small number of adult and nymphs can do a lot of damage. This makes monitoring and timely control strategies crucial for spotting bugs. It is best to monitor trees from all areas of the orchard, but it is important to pay particular attention to trees adjacent to bushland and ‘known hotspots’. Experienced scouts and many researchers have found that spotting bugs will infest the same areas consistently each year. Most orchards tend to have these areas, but only good spatial crop records will provide this information.

The conventional approach is to look for green fallen nuts with internal fresh damage. From December onwards it is important to collect nuts from the tree for damage, as nuts damaged from this time onwards will not be aborted.
The current protocol is as follows:,

Early in the season, sample at least 10 freshly fallen nuts from each tree (and from December onwards sample nuts from the tree). The number of trees examined will vary, but you need to ensure you sample enough trees to determine if spotting bugs are present or absent. One option is to monitor 10 trees in known hotspots and then examine trees randomly across the remainder of the block. You must ensure a minimum of 35 trees are monitored in this arrangement.

To monitor for damage, cut open the nut and separate the husk, shell and kernel. Examine each part for damage. Spotting bug damage appears as a brown lesion on the inside of the husk. There may also be crinkled areas on the developing shell or the kernel is shrunken. The following photos show some typical damage symptoms seen while monitoring.

Some typical damage symptoms seen while monitoring

Sectioned developing nut showing damage to soft shell and developing kernel

Spots on a young nut.

Sectioned nut showing lesion on inside of husk (nut removed) and Nut with glucose rich exudates on the surface that appears after fruit spotting bug feeding

Note figure above shows the glucose rich exudates which osmotically flows to the surface of the nut after the fruitspotting bug has fed on the macadamia nutlet (courtesy I&I NSW). (Other images from Macadamia problem solver and bug identifier © The State of Queensland, (2003)).

Control options

Unfortunately there aren’t any effective bio-control agents commercially available, but research work has commenced into this area. The aim of the research work is to reduce our dependence on chemical control for this pest.

Chemical Control

The currently registered chemicals for the control of fruit spotting bugs are shown in the table over (correct as of 22nd September 2010). Please note that the listing of a chemical here does not mean that MPC or I&I NSW endorses its use or recommends the product. All users of agricultural chemicals must be trained and all applications must be made in accordance with label directions.

Currently Registered chemicals for spotting bug(s) control.

Chemical

Critical use comments

Acephate (i.e. Orthene®) Broad spectrum organophosphate, should not be used at flowering. (not compatible with Trichogramma wasps (Mactrix).
Azinphos-methyl (i.e. Gusathion®) Broad spectrum organophosphate, should not be used at flowering. Best used as part of a bulldock resistance management program (not compatible with Trichogramma wasps (Mactrix).
Beta-cyfluthrin (i.e. Bulldock®) Only 2 applications per season of Bulldock should be made.
Should not be used at flowering (1 spray is compatible with Trichogramma wasp use (Mactrix).
Endosulfan (i.e. Thiodan®) The APVMA has cancelled the active constituent approvals for endosulfan effective from the 12th October 2010, but use of cancelled product containing endosulfan in accordance with label instructions is permitted until 12 October 2012.
Methidathion (i.e. Supracide®) Methidation is a broad-spectrum insecticide and should be used sparingly not compatible with Trichogramma wasps (Mactrix).
Trichlorfon (i.e. Lepidex®) Trichlorfon suffers from alkaline hydrolysis. If using this product ensure you add a buffering solution to your tank (eg LI700).

What about biological control?

There are some known predators and parasitoids of spotting bugs. Unfortunately there aren’t any effective biological control agents commercially available, but research has commenced into this area. The aim of the research is to find a way to establish both parasitoids/predators for the adult and nymphal stages and also the eggs.

A multi facetted approach to spotting bug management will be the topic of future research and a proposal is currently being developed with a number of horticultural industries. This project will look at a range of issues surrounding bio-control, including the mass rearing of a range of egg parasitoids and adult and nymph predators that are known to attack spotting bug (or potentially attack them) but haven’t been successfully reared in large numbers.

As a precursor to this project, a small Voluntary Contribution (VC) project is being undertaken by Bio-resources PTY LTD to look at mass rearing systems for fruit spotting bug. Mass rearing spotting bugs is crucial because many of the known parasitoids are spotting bug specific. To be able to rear the parasitoids in large enough numbers for release into orchards, you therefore need a good supply of spotting bugs. Spotting bug has proven difficult to rear in captivity and so this project will look to find ways to improve this situation.

Where can I access further information?

The following is a list of information sources:

Macadamia Growers Handbook

This reference book contains a large amount of information on all aspects of macadamia production. The section on spotting bugs is very useful.

Macadamia problem solver and bug identifier

This book contains high quality photos and information regarding the identification of nearly all problems encountered in a macadamia orchard.

BioResources Pty Ltd

This website provides information on the new research project investigating the feasibility of a range of parasites for fruit spotting bug. There are some excellent photos on this website. www.bioresources.com. au/FSBbiocontrol

References

Brimblecombe AR (1948) Fruitspotting Bug as a pest of macadamia or Queensland nut. Queensland agriculture Journal 67: 206-211.

Ironside DA (1981) Insect pests of Macadamia in Queensland QDPI publication 81007.

Miles PW (1987) Plant sucking bugs can remove the contents of cells without mechanical damage. Experimentia 43. 937-939.

Miles PW & Taylor (1994) Osmotic pump feeding by coreids. Entomologia experimentalis et applicata 73: 163-173.

Huwer R.K., Maddox, C.D.A. and Purdue, I.M. (2008). Workshop – Pest & Disease Management: Progressing IPM and tackling options for FSB – the next big problem Proceedings of the Australian Macadamia Society Conference 30 October – 1 November 2008.

Acknowledgements

Photographs of fruit-spotting bugs and nut damage by courtesy of Agri- Science Queensland, Dept of Employment, Economic Development and Innovation, www.dpi.gov.au (formerly DPI&F, QLD); © The State of Queensland, (2003).

Using Triclorfon (eg Lepidex) effectively

The following is a report prepared by Kevin Quinlan, Supply Chain Manager for MPC based on a presentation given by Matthew Moyle, Nufarm Territory manager for Northern NSW.

Growers have used Lepidex® for the control of flower caterpillar and reported that the results have been poor. This is believed to be as a result of alkaline hydrolysis. Alkaline hydrolysis causes certain chemicals to breakdown rapidly when they are subjected to high pH conditions.

For example, adding Lepidex® to water at a pH of 8 will cause 50% of the product to breakdown in 63 minutes. This means that the chemical concentration is less than what is needed to give good control. To overcome this problem a product such as LI700® can be added to the tank solution. This product buffers the pH and reduces the breakdown. It is a good idea to test the pH of the water you wish to use for spraying to determine whether or not you need to add a buffering solution like LI700®. Like all other sprays, coverage is crucial for the best results with Lepidex®.

If the pH of your water is low or you add a buffer to reduce the pH, then adding copper based products has been found to cause phtyotoxicity problems in some crops. Research work is being undertaken to test whether macadamias are susceptible to this problem. As a result it is best not to add copper to a tank solution that has been buffered to reduce the pH until this research work has been completed.

Controlling Lace Bug

Article by Kevin Quinlan, Supply Chain Manager NIS.

A field day covering the control of Lace bug and Husk Spot was held on the 8th July 2009 at Dick Campbell’s orchard in Alstonville. The following is a brief report on the findings from the day.

The key messages from all speakers were:

  1. Monitor your flowering to see if you have lace bug present.
  2. You will only need to apply a control option if there is lace bug present.
  3. If applying control options, you need to do so in a manner that does not impact upon pollinators, especially bees.

Macadamia Lace bug identification and the damage it causes.

Ruth Huwer & Craig Maddox (NSW DPI)

There is little known about macadamia lace bug which has emerged as a serious pest in some orchards over the last few seasons. Macadamia Lace bug (Ulonemia concave) is a small insect, with adult lace bugs being up to 3-4mm in length (figure 1). These insects are sap suckers. They suck the sap from flower buds, which causes the flowers to desiccate. This insect has the ability to cause crop failure in orchards if it is not managed.

Figure 1. An Macadamia Adult Lace Bug

Figure 1. An Macadamia Adult Lace Bug

Figure 2. Macadamia Lace bug Nymphs.

Figure 2. Macadamia Lace bug Nymphs.

The life cycle of Macadamia lace bug has not been studied in detail, but it is estimated that it is between 12-18 days. Lace bugs have been found to survive at temperatures as low as 5°C, giving them the ability to over winter in cold locations.

The eggs of lace bug are laid in the florets of flowers. These eggs hatch and the nymphs (figure 2) move up and down a flower raceme, feeding on developing flowers. These nymphs are yellowish to brown in colour. As the nymphs progress through their lifecycle stages they shed skins that are attached to flowers. These skins can be found on desiccated flowers that they have fed on, which indicates the cause of the racemes death.

The complete host range of macadamia lace bugs is unknown. Currently there is a university student studying the alternative hosts for lace bugs.
The typical damage that lace bugs cause is the death of florets on flower racemes (figure 3). The loss of significant numbers of flowers can have serious ramifications, with crop losses of up to 90% being observed.

Figure 3.1 Typical damage symptoms caused by macadamia lace

Figure 3.1 Typical damage symptoms caused by macadamia lace

Figure 3.2 Typical damage symptoms caused by macadamia lace

Figure 3.2 Typical damage symptoms caused by macadamia lace

As this pest has a very short life cycle and numbers can build up rapidly, it is crucial to monitor flowers closely to detect if the pest is present. It is also crucial to monitor so that you only spray if there is a problem, as there is a risk of reducing pollination. Spraying at flowering has rarely been used in the past due to the large numbers of pollinators present in orchards, especially bees. This makes it necessary to apply any chemical control at a time that curtails the potential impact upon bees and other pollinators.

You must only spray when bees are not actively foraging. This is usually late afternoon/early night depending upon weather conditions. Currently the only chemical control option registered for lace bug is Endosulfan. Endosulfan has an effective life of approximately 8 hours. This means that if pollinators are not active for 8 hours after application there is a low chance of killing these insects. Trichlorfon (eg Lepidex®) is registered for the control of macadamia flower caterpillar, another flower pest. This chemical has low bee toxicity if applied correctly. It also has a low residual life. The same timing issues for this chemical as those for endosulfan apply.

How do I monitor and when do I spray for lace bug?

Alan Coates, Consultant.

Alan has found that lace bug activity has increased considerably over the last 6 years, with the last couple of seasons having considerably higher levels of activity. Lace bugs feed on flowers and they can also feed on small nutlets. They attack throughout all flower stages. If damage has been found in an orchard previously, then it is likely to occur again. This makes monitoring crucial.

To monitor, look for damaged flowers (figure 5). The most obvious sign of lace bug activity is the death of florets on the end of a raceme but you can also have florets die anywhere on the flower from attack.
It is best to check flowers weekly, as lace bug numbers can build up very quickly. There can be hotspots within orchards and it is important to look to see if there are any of these in your orchard. These can be treated to stop the spread of lace bug and minimise damage across the entire orchard.

Figure 4. Lace bug damaged flowers found during monitoring.

Figure 4. Lace bug damaged flowers found during monitoring.

A control threshold has not yet been developed for lace bug. Research into what levels you should find before applying controls is required. From experience Alan looks for damage to flower racemes and then adds up the number of flower racemes found with damage. He then bases his recommendation upon these counts and also the flowering intensity and flower stage.

As lace bug has a short life cycle and you can have multiple flowerings it may be necessary to apply control options more than once. This makes monitoring very important to ensure you know where the activity is in the orchard and to ensure good control. It is best to apply any control options late afternoon/evening time when the bees are not active in the orchard. If you have bee hives on your farm, talk to your beekeeper about what you are planning to do if you have a lace bug problem.

Monitoring results have found that lace bug is active in orchards from early July to October, so it is important to start monitoring early. This will allow a good picture of what the trend is in your orchard to be picked up. Monitoring may show that there is no lace bug present and so there is no need to spray.

Macadamia Nut Processing