AppleTalk Conference Call Summary
Tuesday, June 5, 2018, 8:00 – 9:00 AM
Guest speaker: Matt Grieshop, Michigan State University, Associate Professor Organic Pest Management
Presenter: John Aue, Threshold IPM
Moderator: Peter Werts, IPM Institute of North America; questions or comments, pwerts@ipminstitute.org
June 5th Call Stream: https://fccdl.in/Ootg4I1t8k
Interview with Matt Grieshop
Current research
Matt is an entomologist focused on organic pest management and works with weed management and disease management. A primary focus of his most current research is the evaluation of sanitation and elimination of potential spotted wing drosophila hosts in processed fruit wastes. These include apple and grape pomace, which often host late-fall generations of spotted wing drosophila. Controlling late-fall generations limits the number of insects that can overwinter and reduces spring populations. Matt’s research has focused on limiting spotted-wing drosophila growth in these hosts through burial and composting. His lab is also studying the spotted-wing drosophila’s unique bladed ovipositor, a piercing tube for laying eggs that Matt thinks may eventually contribute to the insect’s ability to target thicker-skinned fruits through selection.
Could you give a brief update on the Solid Set Chemigation System for trellised orchards?
Matt is involved with evaluating a fixed agrochemical delivery system that would allow rapid application of insecticides with virtually zero worker exposure. This application technology would be valuable to apple growers because typical biopesticides are most effective when applied several times at low dosages rather than fewer high-dose sprays with tractor-based sprayers. The solid-set canopy delivery system proof of concept rivals conventional air-blast sprayers with significantly more canopy retention and limited non-target drift. Nozzles have been upgraded to include a rotary component for optimized dispersion.
Insect management
Can you share a few insights into plum curculio behavior and biology that we may not have considered?
Matt does not think PC is moving in and out of organic orchards, comparatively it is presumed that in conventional orchards PC comes from edge habitat, however, we should not rule out the possibility that conventional orchards could also have resident PC populations.
For every scarred fruit found at the end of the year, there was likely an egg laid that didn’t mature to adulthood. In fact, only about 10-15% of apples that are abscessed have a larva in them. When the fruit is distorted physiologically and has many scars, larvae are much more likely to be present.
What are the latest updates on the use of OMRI insecticides against plum curculio and apple maggot? Many growers are interested or have been trying Venerate.
Apple maggot does not appear on the label for Venerate. Likewise, efficacy data in published studies for Venerate on plum curculio (PC) have been poor at similar levels to Entrust. Management of plum curculio typically begins when the insects have already reached adulthood and developed strong defenses. Imidan kills PC relatively quickly, but even when full rates are applied, large populations from outside sources will still be able to inflict significant damages to select varieties. Organic systems are even more at risk, especially if an in-house population develops and expands. These orchards are likely to show PC damage uniformly, while conventional orchards usually only experience damages near the perimeter. Even if the neonicotinoids and diamides don’t prevent the female from laying an egg, the larva will usually still be killed.
Do you have any insight into combining Surround with another insecticide to control plum curculio?
Effective conventional pesticides act as a contact poison when readily absorbed into PC exoskeletons, most organic products are poor contact poisons. Surround irritates insects, causing them to remain in flight for longer periods of time and encourages the PC to frequently move around the orchard, continuously repelling them and preventing egg laying. This frequent movement may result in PC either not laying eggs at all or dumping all eggs in a single location. When the eggs are dumped in a single location, this will isolate crop damage to a few fruit. It is also possible female PC will expire before they have been able to complete their egg laying.
Plum curculio spends the greatest amount of time in its life cycle as pupae in the soil or leaflitter. This is the widest window of time to manage PC populations with organic floor management. A more complex floor structure with a succession of weeds provides good resources for pollination and for natural enemies, but it also provides a good habitat for PC to overwinter. Animal integration and other sanitation is important to reduce PC by disturbing soil when rooting for grubs and high-protein foods. In terms of controlling PC at the edge of orchards from an external host, there might not be a good organic management method. Surround, when accompanied by a mild allopathic or toxic pesticide, might be a good approach, although research into organic plum curculio control is limited.
Two years ago, you discussed using pathogenic nematodes for PC management. One of our growers contacted Art Agnello at Cornell and in their trials in New York; they and have not been able to obtain reliable kill of PC in the soil with nematodes there.
Resident populations are much more likely in organic systems because these growers do not have good insecticides to intercept PC on the perimeter. The way forward for managing PC outside of the adult-life stage includes the following options: 1) Removal of infested fruit before larvae moves from fruit to soil; and 2) mechanical destruction of pupa in soil, e.g., cultivation for weeds, Matt has seen slight reduction in PC where strip cultivation has been used or where pigs have been used; and 3) use a bio-pesticide approach where soil is inoculated with microorganisms, e.g., entomopathogenic nematodes. Some of these are commercially available and marketed as a plant health supplements so suppliers can avoid EPA pesticide-registration requirements.
Art Agnello hasn’t published results on these trials, despite some promising extension literature using a nematode collected from local alfalfa weevils. The biggest problem from the organic standpoint is that OMRI-compliant packages aren’t offered anymore – shelf-stable nematodes have a petroleum stabilizer and therefore not OMRI approved. Cheaper nematodes are available in gel stabilizers; however, this has not been certified by the National Organic Program (NOP). This leaves producers with another novel and real option: GROW YOUR OWN. Find out how to Rear Nematodes for Biocontrol from MSU OPM, here: https://www.youtube.com/watch?v=kSDQbJRh0Ss.
Apple producers can reasonably grow their own nematodes by infecting waxworms from a bait store, since use of these nematodes is not regulated by EPA. We can determine which nematodes are present based on the different colors the waxworms turn, when they are infected. Nematodes have two life stages and are not in the reproductive stage until they are in their host. We can expect about 100,000 to 200,000 nematodes to be produced per waxworm and the nematodes need to be applied at a rate of a hundred million per acre. There are not likely enough hosts in soil to sustain populations, so two applications when PC are leaving fruit and moving into soil would likely be needed. Nematodes do not perform well in heavy clay and do well in soils with lots of organic matter. In lab trials these nematodes seemed to attack everything, but once in the field it appeared they did not attack as many other pests, e.g., Japanese beetle larva.
Research by Peter Witzgall in Switzerland found that codling moths were more likely to lay eggs on apples with a high quantity of naturally occurring yeasts, and when yeast is present where the larvae are, they are more likely to succeed. Matt speculated that this may also be true with PC. Aphids produce honeydew because a large quantity of sugar syrup must be processed to obtain adequate levels of nitrogen. Yeast is well adapted for scavenging nitrogen out of low-nitrogen environments, making them beneficial sources of nitrogen to insects in apples. Based on observations that PC damage is more common in orchard perimeters, the insect was speculated to move in and out of the orchard seasonally. This, according to Matt, is not the case; our tools successfully kill the eggs, and the damage at orchard edges is due to new insects from external sources moving in, which is supported by evidence seen in organic orchards.
Do we know if BeetleGONE for Japanese beetle control during late summer might provide some suppression of resident PC/AC populations?
Bacillus thuringiensis (Bt) works best on larval insects when they are small and consuming large amounts of plant tissue. Adults do not feed nearly as much, which significantly reduces the likelihood of consuming enough Bt for a lethal dose. Upon consumption, the protein moves into the insect gut where it unfolds under certain pH conditions. Once unfolded, the protein latches onto certain receptors in the mid-gut, ultimately causing sepsis if enough Bt is consumed. Even if the adult consumes enough plant material for a lethal dose, a slightly different gut pH or lack of proper receptor sites could render the protein ineffective. The reason BeetleGONE works so well on Japanese beetle because they intake so much plant matter that even if the treatment is working poorly, they’ll consume enough to kill them. Matt believes PC may have other undiscovered needs that may offer an opportunity to control the insect such as nuances in their microbiome or in the complex stridulatory organs and hearing receptors.
Any recommendations on organic brown marmorated stink bug management?
For organic management, brown marmorated stink bugs (BSMB) are seemingly impervious to the available insecticide options. Their mouth parts are essentially a straw, making poison difficult to deliver. Sorghum and sunflowers seem to be good trap crops for reducing damage to orchards, when planted around the perimeter of an orchard. The other possibility is implementing ghost traps, which are deltamethrin-treated mosquito nets stuck over a pyramid trap baited with the BMSB aggregation pheromone. From an organic perspective, these traps need to be set 25 yards outside of buffer rows to secure NOP certification. Within the buffer, trap crops that flower near the time protection is needed can be set to attract any bugs that infiltrate the ghost-trap perimeter.
Can you discuss rainfastness of the codling moth virus and any other insights to using the granulosis virus?
Granulosis virus, e.g., CYD-X, can be applied in scenarios that require a short pre-harvest interval since it can be applied up to and including the day of harvest. Granulosis virus is not fast acting and some injury can still be caused by infected larvae before they die. If you’re using codling moth virus, the lowest-labeled rate should be put out frequently, e.g., where the label says two-to-six-ounces may be applied, two ounces should be applied at a higher frequency. For orchards that experienced heavy flights soon after their biofix date, larvicide should be applied at 250 degree-days, and reapplication during the first ten days of the hatch period would be determined using the recent trap captures after the biofix.
For organic growers, multiple applications of insecticidal or horticultural oils can be effective on codling moth during egg laying in the second generation at 1150-1250 degree-days. However, these should be avoided if sulfur has been used within 14-days. Oil applications of one percent are cheap and can also provide relief after mite flare-ups. Another option is to start at 1150-1200 degree-day with an oil, switching to virus application on a weekly rotating basis.
San Jose scale
Anyone worried about San Jose scale, should begin monitoring crawlers. Scaffold branches should be taped using black electrical tape with petroleum jelly applied on top of the tape. These tapes will need to be checked more often than double-sided carpet tape because the crawlers will discolor in the petroleum jelly and, in a short amount of time, will be indistinguishable from bits of bark and other debris that may land on the tape.
The Jentsch lab blog posted that spotted-wing drosophila had been found in sweet cherries in New York; have you noticed any spotted-wing drosophila yet?
Matt hasn’t heard of reports in crops, but he has seen positive hits in trapping networks. If spotted-wing drosophila was a problem last year, close monitoring may not be necessary for both organic and conventional growers. Strawberries and floricane raspberries might require monitoring, but for cherries, blueberries and late raspberries, infection can be assumed – it’s almost like a disease.
The MSU monitoring network has also caught spotted-wing drosophila this year, and the blog post from the Jentsch Lab can be found here, https://blogs.cornell.edu/jentsch/2018/06/04/nys-ipm-spotted-wing-drosophila-monitoring-program-swd-adults-found-in-tart-cherry-wayne-county/.
Disease management
Ozonated water
Matt has begun working on evaluating ozonated water as a tool for disease management within the last month. He envisions fully-automated ozone applications enabled by solid-set application systems. Application of ozonated water is not NOP-compliant, although Matt suspects this is due to limited research on the practice. Preliminary observations suggest the treatment isn’t very effective against apple scab, but laboratory studies seem to have shown good lethality on spotted-wing drosophila.
Do you have any experience using Potassium Bicarbonate (aka: Milstop, Kaligreen, Armicarb) against apple scab or other diseases? If so, what rates were effective?
Published studies typically showed 70-75% control of apple scab with potassium bicarbonate with a smaller environmental risk than the common sulfur alternative. Applications offer summer disease control alongside secondary scab spread and can be used in heat as opposed to oil. One group using approximately 4.4 pounds-per-acre of potassium bicarbonate reported control comparative to typical sulfur control.
For further information on the use of newer soft fungicides against our summer disease complex, read Patty McManus’s article, “Killing Them Softly: Do Soft Fungicides Work on Apple Diseases?†which can be found on pg. 9 of the May 18th issue of Wisconsin Fruit News in pdf form, here: https://fruit.wisc.edu/wp-content/uploads/sites/343/sites/36/2018/05/Wisconsin-Fruit-News-vol3-issue3.pdf
