AppleTalk Conference Call Summary
Tuesday, July 12, 2016, 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
July 12th call download: Click Here
Current degree-day (base 50°F) accumulations for codling moth biofix dates, May 23 – 27
- Gays Mills, WI: 887
- La Crescent, MN: 953
- Lake City, MN: 920
- Hastings, MN: 935
- Woodstock, IL: 988
Organic – insect management
Chemical management of arthropods:
- What do you know about some of the new or promising OMRI approved insecticides for apple maggot, plum curculio, aphids and leafhoppers; specifically Grandevo and Venerate? Organic producers are struggling with the secondary pests in high-density plantings.
- Matt is some skeptical of Venerate (Burkholderia spp.) and Grandevo (Chromobacterium subtsugae) because they are primarily stomach poisons. Spinosad, e.g., Entrust, seems to work best in organic.
- Apple maggot trap out: Is there new information on apple maggot (AM) trap out? Have you done any recent studies on this which can better define a rate per acre for traps and efficacy of trap out?
- At least 400 traps are needed per treated acre, i.e., edge v. entire block, for effective trap out. Most growers use the cost-effective alternative of red Solo plastic party cups rather than commercially available red spheres traps. Deploy traps/cups midway in the canopy before the flight begins since the females will respond to traps before they can lay eggs. GF-120 is a bait spray, with spinosad, that growers in the West use yet it doesn’t have much utility in our region due to the limited rainfastness.
- Borer pests: For the small grower, the best option might be to dig out dogwood borer (DWB) and could also be a good target to use nematodes. Nematodes can behave differently and some species cruise around more and will actively target prey, these would be best for DWB and include Steinernema riobrave. Cultural practices to manage DWB include trunk mounding soil above burr knots. This can have other negative impacts, e.g., increasing vigor, but will help prevent DWB oviposition.
Plum curculio:
- Most organic producers are using Surround (kaolin clay) as the primary defense against plum curculio (PC). Typically one or two coats are needed to provide adequate protection. Additional applications are required as needed based on fruit growth and rain events. It appears the rainfastness of Surround has improved in recent years and may help minimize frequency of re-application. Surround does not kill insects, rather it makes habitat less favorable for egg laying.
- Another option for growers to consider is establishing a trap row on the perimeter and maintain frequent pesticide applications to these trees. Varieties, such as, Liberty are a good choice because it blooms early, is attractive to PC and has scab resistance. Matt has not been too impressed with PyGanic (pyrethrins) for controlling PC or other insects in orchard environments. PyGanic has a very short residue and he has observed mites flair up where PyGanic is used often and notes that PyGanic can be devastating to predatory mite populations. Matt noted conventional and organic producers have had increasing problems managing PC because of a lack of effective insecticides.
- Mass trapping of PC has not been replicated and while Matt does not rule out the possibility, it has been too difficult to research because of the number of orchards required to generate enough results for statistical analysis. Certainly if growers are interested in putting out many traps, it could work, but Matt does not have an exact number traps per acres that would be required to test this.
Nema-WHAT? Yes, you heard me, nematodes! Matt would like organic and conventional growers to consider that managing PC when they are in the soil and fruit is a huge missed opportunity. Plum curculio only spend two to three months as adults above ground, but nine months in the soil or fruit. We should consider the environment that is suitable for PC pupa to develop are also the best conditions for pathogens and nematodes that feed on developing PC pupa.
- 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. Resident populations are much more likely in organic systems and organic 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. Unfortunately there is no affordable OMRI approved formulation, e.g., $400/acre. Shelf stable nematodes have a petroleum stabilizer and therefore not OMRI approved. This leaves producers with another novel and real option: GROW YOUR OWN.
- MSU OPM: How to Rear Nematodes for Biocontrol, 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.
Japanese beetle
- Japanese beetle (JPB) is an invasive insect and typically with invasive pests in agriculture there are 10-15 years of really bad pressure and after this period pest pressure becomes variable. Matt thinks populations may be partially managed by bacteria and protozoa that eat female ovaries. Matt reminds us there is a larger lesson regarding invasive pests. There have been seven or eight species that have been predicted to ruin some sector of agriculture over the last decade. The reality is none of this has come to fruition and most of the time invasive species develop natural controls after 10-15 years. The exception to this would be the citrus psyllid and subsequent citrus greening disease that has impacted that industry.
- Milky spore is one pathogen that has been found to manage populations of JPB, however soil inoculations are hard to test in field and need lots of farms. This pathogen has seemed to work best in hotter climates and perhaps in a few years milky spore would be an option in the upper Midwest.
- Attract and kill could also be a viable option for JPB management. Deltamethrin + pheromone could be used. Deltamethrin is available in a dust formulation that could be added to the traps. Note: Do not located JPB traps in your orchard since JPB release an aggregation pheromone when they find an ideal food source, e.g., put them in the neighbor’s yard or the other end of an adjoining field.
Disease management
- Are there any new OMRI approved fungicides for management of summer diseases and fruit rots growers could be considering?
- We have a good opportunity to manage scab when it is in the overwintering stage. Apple scab spends nine months on the orchard floor and sometime between leaf fall and spring is when scab sexually combines. Every year we are literally getting new scab biotypes each spring. Male and female mycelia reproduce to create new, improved apple scab. If we can destroy leaf scab by flail chopping or applications of urea to speed up decomposition we reduce the ability for new scab biotypes to form. Consider that we want to intercept scab before primary scab release and taking away chance to develop resistance biotypes. We can also fight 100,000 spores per acre instead of 1 million. Options include to windrow leaves and chop with a flail mower, apply urea or burn. This research began in Canada in the 1960’s where nitrogen applications were used to reduce scab. This work demonstrated that in a lab when apple scab was exposed to free nitrogen, e.g., urea, reproduction was shut down and decomposition was sped up. A late season application to the ground and trees in a 10-15% solution is adequate. Note: Organic growers cannot use urea. There has been some evaluation of compost tea and non-urea control in the studies, results were variable and did not provide a similar level of breakdown. The main challenge with compost tea is getting consistency.
