An integrated pest management program for the Australian almond industry (AL16009)
What’s it all about?
Beginning in December 2017, this investment is tasked with helping growers tackle the problem of insect pests and the damage they cause almond crops both in the orchard and after harvest. With a focus on integrated pest management, the program is developing a toolkit of practices, technologies and guidelines to help growers reduce insect populations, with areas of investigation including…
- Improved orchard hygiene and mummy management
- New ‘attract and kill’ technologies that target damaging Carpophilus species and female carob moths
- Improved mating disruption for carob moths
- Pesticide options that are more compatible with an integrated pest management approach
- Improved understanding of pest species and their natural enemies (biological controls)
- Improved post-harvest disinfestation and monitoring.
Five new blends of three pheromone compounds identified from the almond carpophilus beetle were field-tested for attractiveness to this pest. The best blend attracted 19 times more of this beetle than a commercially available blend that has been used in almonds. Assessment is underway for the cost-effectiveness of this new blend in a mass trapping system for carpophilus beetle.
A field trial to assess the effect of trap colour/design on the catch of carpophilus beetle in almonds was undertaken. Results showed little difference in the total weight of beetles caught, between seven trap types. Traps with clear buckets had the advantage of catching far fewer earwigs which usually impede the processing of trap samples. If clear traps prove to be as efficient as other colours in trapping the almond beetle specifically, their use will streamline future trapping studies considerably.
One synthetic lure for female carob moth out of 11 lures was found to significantly outperform the rest, showing some promise towards the development of an effective female lure. Field trials also showed that clear traps are significantly more effective against male carob moths compared to seven other trap colours, including the industry-standard white trap. Clear traps also appeared effective for trapping female carob moths. Matte clear traps appear to have a slight advantage over gloss, in terms of the greater catch of male carob moth and lower catch of non-target insects.
Monitoring of four commercial stockpile fumigations during the 2022 harvest season found that none achieved the combination of fumigant concentration and duration required for effective disinfestation, confirming earlier results. Postharvest studies also confirmed that the rust-red flour beetle Tribolium castaneum is not simply a secondary pest but can initiate and cause significant damage to almond kernels in storage and should be managed accordingly.
The project team report progress in the following areas:
- A season-long ‘attract and kill’ 14-plot trial was established at a commercial orchard in the Robinvale region. The trial assessed kernel damage during mass trapping of carpophilus beetle using the best co-attractant (from previous work) with a standard tri-species pheromone lure. Nut samples were collected at harvest, with the beetle and nut samples now being processed.
- A second field trial was established to assess field replacement frequency for the best co-attractant solution for carpophilus beetle. Trapped beetle numbers were recorded daily for three weeks after the commercial harvest. Analysis is now underway.
- The literature review of pesticide off-target impacts was completed to help producers identify pesticides that may be less disruptive to IPM programs.
- Entomopathogenic fungi have been identified as having potential for management of carpophilus beetle. The team screened seven strains of Beauveria bassiana, a fungus used in agricultural pest management. The research showed some potential for use as biopesticides within an IPM strategy, with beetle mortality levels of 19 per cent for adults and 73 per cent for larvae.
- 90 bioassays with 1,452 individual larvae were performed to monitor the efficacy of phosphine gas fumigation as a treatment for Indian meal moth (Plodia interpunctella). The discriminating dose was found to be 0.09 ± 0.005 mg/litre (66 ppm) of phosphine for 20 hours. Results also indicated that Indian meal moth resistance to phosphine is scarce, and current fumigation protocols are adequate.
- Field trials of synthetic attractants for carob moth during summer 2020/21 assessed 12 blends selected from 20 different compounds. The best blend that consistently attracted female carob moths is being refined in laboratory studies, with improved formulations to be field tested in the 2021/22 season.
- A field trial to assess colour attractiveness of delta traps found that transparent traps caught significantly more male carob moth than six other colours (including white). More studies are planned to clarify whether transparency or gloss is the key factor, and whether the results also apply to female carob moths using food lures.
During the third year of this project, the project team has made progress on the following activities:
- Four field trials tested the best two new carpophilus co-attractants from the previous season’s field trials and some variants, demonstrating an eight to 10-fold increase in catches of and greater specificity for the damaging carpophilus species. Further field evaluation will be conducted in the 2020/21 season.
- A large-scale trial compared two different hygiene practice options to eliminate mummy nuts from the orchard floor – removal (sweeping, pickup and off-site disposal) versus equipment that pulverises nuts on-site (Seed Terminator). The results showed both options as being equally effective against kernel damage by carpophilus beetle and carob moth.
- Two putative pheromones were identified from the species of carpophilus responsible for almond kernel damage, which are hoped to contribute to an increase in trap efficiency, with further research to be conducted.
- Field trials of synthetic attractants for carob moth are underway, assessing the attractiveness of 12 chemical blends to carob moth under orchard conditions
- The team investigated the use of alternative chemical treatments to stockpile fumigations, finding these are currently an unviable option for reasons of cost, practicality and safety. Fumigation and non-chemical alternatives plus sound on-farm crop management remain important components of almond post-harvest management to minimise the risk posed by insect pests in storage.
- A field trial assessed the effect of burial depth on the emergence of carpophilus beetle and carob moth from infested nuts, which were buried in May 2019 and monitored fortnightly for six months. Carpophilus beetle emerged from nuts buried at the maximum depth (90cm) indicating that considerably deeper burial is required to prevent emergence, while carob moth did not emerge from nuts buried deeper than 30 cm.
- Research findings were delivered to 55 industry participants at field sessions for orchard managers and technical staff in the Robinvale and SA Riverland districts in December 2019. A workshop planned for autumn/winter 2020 did not proceed due to COVID-19 restrictions, however findings from the 2019/20 season were delivered at an ABA IPM webinar in late 2020.
- Some restrictions to post-harvest studies and field research occurred due to COVID-19 travel restrictions, however the team aim to make up any lost time in the coming season.
The project team continues to work on several field trials investigating insect pests in almond crops, the damage they cause and potential management options.
A key recent finding from a second spatial analysis survey was that mummy nut infestations were highly clustered suggesting that targeting mummy nut hotspots with hygiene practices could have merit. They also found that carpophilus infestation in mummy nuts was also highly clustered in the season with higher population densities, and associated with mummy nut density, further confirming that targeting mummy hotspots could be warranted. By contrast, carob moth infestation of mummy nuts was randomly distributed.
They also report that significant progress has been made on developing a new carpophilus lure with several new synthetic ‘co-attractant’ (food attractant) blends developed and the fields results demonstrating that these new blends are more effective and specific to the target species than currently available methods.
Don’t forget that this project has already delivered a number of useful resources for growers that are available in previous project updates.
The research team reported progress in the following areas:
Laboratory and field screening for carob moth biocontrol
The research team investigated the ability of a commercially reared Trichogramma wasp species, T. pretiosum, to parasitise carob moth in almonds. Under laboratory conditions, the wasp was found to destroy carob moth eggs by either parasitism or host feeding, showing promise as a biological control agent for this pest.
However, when the team studied the wasp’s activities in a field trial, where T. pretiosum was released in an almond orchard in the Sunraysia region, the wasp did not parasitise the carob moth. There are several reasons why this may have occurred, such as the wasp eggs being damaged by the release methods used, the wasp eggs being eaten by other predators such as earwigs or that the wasps cultured in a lab are less effective at detecting carob moth eggs.
An additional study was set up, dispensing egg capsules in grape vineyards, citrus and almond orchards, which was successful.
The team took the opportunity to collect another species from the field, the native T. carvarae, to investigate in the future. It may be better adapted to the Australian environment.
Further work is needed to investigate reasons for the ineffective trial and to evaluate and compare the effectiveness of different Trichogramma species.
Desktop review of alternative control options
The team conducted a review of alternative pesticides for insect control in almonds. The review has three parts:
- A detailed technical review investigating particular types of fungi, that attack insects, as biopesticides for Carpophilus beetle. It is hoped that the fungi could be spread throughout an orchard by insect species that are attracted by a lure. The team is developing ways to test the fungi.
- Results of a literature search on the use of neem as a technology for controlling Carpophilus beetle and carob moth in almonds. Neem oil derived from the seeds of the neem tree has a long history of use in India as a pesticide, cosmetic, and natural remedy.
- Identification of other possible pesticides, with the team listing active ingredients, mode of action, where they are currently in use, target pests and pest physiology, targeted pest in almonds, and toxicity and impact on key natural enemy species.
Almond IPM workshop
In May, the researchers held an Integrated Pest Management workshop for almond producers in Irymple, which was attended by orchardists from the South Australian Riverland, Victorian Sunraysia and NSW Riverina districts. Fact sheets produced for the workshop are available below.
Growers can learn more from these fact sheets:
- Monitoring carob moth - update
- Monitoring carpophilus beetle in almonds - update
- Carpophilus beetle and carob moth in almonds - a visual guide
- Impact of pestcides and fungicides on beneficial species
Read about alternate control options in further detail by downloading the alternative pesticides review.
Since the last update, the project team has continued to advance many different research areas that will help growers to improve pest management in almonds. Details below.
Lure and pheromones for Carpophilus beetle
The first prototype of a lure for Carpophilus beetle has been developed based on odours of known attractants, and is ready for field tests to look at its effectiveness compared to the currently available commercial blend.
Pheromone research for Carpophilus beetle is also underway to identifying active (and inactive) components from the commercial tri-species pheromone blend.
Several new slow-release sachet dispensers have been designed to provide a longer-lasting effect, and field testing of the new prototype co-attractant formulations and dispensers, as well as the current formulation, has begun.
Partition sampling of nuts
The project team has undertaken research to look at the distribution of kernel damage caused by carob moths within almond trees, to find out where pest control efforts are best targeted.
This study is now complete, with researchers finding no difference in damage levels between east and west sides of the trees, but a six-fold difference in damage levels between nut samples from low compared to high in the canopy, with significantly greater damage at height.
Recommendations for growers:
Where carob moth is to be managed by pesticide application, growers should ensure that the set-up of equipment, application speed, water rates and even tree structure, are optimised for delivery of the spray to the upper canopy.
Researchers also recommend that where damage assessments of new crop nut samples are taken for decision-making on orchard and crop management practices, and for the interpretation of field trial results, nuts should be collected from throughout the height of the canopy, not only picked by hand.
Spatial analysis of mummy infestations
Between growing seasons, both Carpophilus beetle and carob moth feed and survive on mummy nuts. Consequently, sampling these nuts in autumn/early winter would allow growers to estimate the distribution and prevalence of these pests across their orchards, and help prioritise orchard hygiene activity and prepare for in-season pest management.
Researchers made a spatial analysis of mummy infestations by these insect pests on 133 almond trees across a 20-hectare block. Heat maps were generated to allow the team to visualise the spatial distribution of mummy nuts and pest infestation within the block, and the team used these to successfully estimate infestation of unsampled trees.
The spatial analysis of carob moth infestation in winter mummies shows that infestation is clustered. This information will be used to improve the reliability of sampling in both orchard and research contexts.
Recommendations for growers:
In the orchard, remove or destroy (such as by mulching) ground mummy nuts to reduce Carpophilus beetle infestation of mummy nuts.
Nuts to assess carob moth infestation should be taken from the trees and nuts to assess Caropophilus beetle infestation should be taken from the ground.
The presence of infestation hotspots within the block, for both species, means that sampling methods need to be optimised to avoid missing critical areas of infestation, for example sampling just one row of trees per block is not sufficient to capture the variability in infestation.
Super wetters to improve the spread of chemicals
Both pest species infest the hull and kernel of mummy nuts, entering the new crop through the hull split. The presence of mummy nuts in the orchards is in part due to fungal diseases such as hull rot (Rhizopus stolonifera) which cause nuts to remain on trees after harvest. Commonly, growers deal with the pests by spraying trees with insecticide.
Insecticides and fungicides are more effective if sprays penetrate the split of the hull to protect the exposed hull and shell against larval or fungal development. Researchers tested a class of spray adjuvants known as super wetters, to find out if they could better deliver the chemical into the hull splits of green almonds. This has not been researched before.
In comparison with a standard wetter, the researchers found that a super wetter increased the spread of solutions significantly, but solutions were only detected inside the hull split when the split was facing directly towards the sprayer.
Female carob moth lure
A female carob moth can lay up to 200 eggs on mummy nuts throughout winter and spring so a female moth attract and kill system would provide reduce carob moth numbers prior to hull split, thereby reducing damage to the new crop.
A previous study which began work on the preferences of female carob moths found that larval rearing diet that had previously had a cohort of carob moth larvae feed upon it and emerge from it was attractive to female moths for egg laying. This work sought to confirm the attractiveness of the media compared with almond mummies. In total 13 trials were run, finding no that the used media was just as attractive as mummy nuts to the moths. Next steps for this project is for a chemist to identify the underlying volatiles that make the media attractive, with a view to using them in lures.
Report on biocontrol of pests
A report on natural enemies for almond pests with potential for biocontrol has been produced. The report reviews the current literature on biocontrol of carob moth and Carpophilus beetle and also presents the findings from a field survey on natural enemies of almond pests, conducted in winter 2018. The report paves the way for next steps to address knowledge gaps and test particular species for biocontrol potential.
The researchers report that all avenues of investigation are established, including the development of a new attract and kill technology for Carpophilus near dimidiatus – identified in earlier crop surveys as the Carpophilus species responsible for the vast majority of kernel damage.
The project team is exploring an improved co-attractant to better target this insect, beginning with chemical analysis for odours from developing almonds, mummies, nuts, and associated yeasts. Pheromone research for Carpophilus near dimidiatus is also underway, while a new attractant dispenser – a polyethylene sachet – has been designed to increase the effectiveness and longevity of the current attractant used. This is being field tested during the 2018/19 season.
In orchard hygiene work, field studies commenced in late July to feed into the development of scientifically validated guidelines for mummy density versus insect damage at harvest.
As the presence and abundance of mummies is a major factor relating to Carpophilus and carob moth population densities in orchards, the guidelines will help inform growers of the likely need for scaling up of insect pest controls.
Research to assess insect infestations in windfall nuts has also commenced, while preliminary work that has demonstrated survival of Carpophilus beetles in mulched nuts.
In the post-harvest space, the team began by visiting almond processors and collecting insects for culture (Indian meal moth, red rust flour beetle). Meanwhile biocontrol work is also underway, with field surveys in four orchards where traps are currently being monitored, mummy nuts are being collected for insect identification and emergence studies, and insects are being identified by a diagnostics team.
With program activities getting underway and the first official update due to Hort Innovation shortly, look for updates in future editions of Hortlink and in industry channels. You can expect to see plenty of opportunities to engage with the program as it progresses, with the investment set to include the use of demonstration blocks, on-farm trials, training workshops, field walks, fact sheets and videos.
An overview of the program was also provided in the autumn 2018 edition of In A Nutshell.
This project is a strategic levy investment in the Hort Innovation Almond Fund