AppleTalk Conference Call Summary
Tuesday, May 30 2017, 8:00 – 9:00 AM
Presenter: John Aue, Threshold IPM
Moderator: Peter Werts, IPM Institute of North America; questions or comments,
May 30th Call Stream: CLICK HERE
Dicamba-tolerant soybeans
The Environmental Protection Agency approved the use of Monsanto’s Xtendimax (dicamba) herbicide for use on Roundup Ready 2 Xtend (glyphosate and dicamba tolerant) soybeans in 2017. Although most soybean growers in our region are less likely to have issues with herbicide-resistant weeds, since they are not growing them year after year, and may not have use for planting dicamba-tolerant soybeans, it is important for apple and grape growers to be aware if this herbicide is being applied near their fields. The new formulation is supposedly less likely to volatilize after application, yet there is nothing unique in the product that will affect physical drift during application. Dicamba drift can injury grapes a half mile or more from application site. If you have soybeans planted close to you, it is recommended to contact your neighbor to voice your concern and see if they are planting this type of seed. For more information visit: What You Need to Know About Dicamba-Tolerant Soybeans in 2017, http://www.agriculture.com/crops/soybeans/what-you-need-to-know-about-dicamba-tolerant-soybeans-in-2017.
Plum curculio
Plum curculio (PC) movement and egg-laying activity is temperature dependent and requires several days of warm nights in the 55-65°F range to really get movement. Plum curculio adults will continue to damage fruit and move among trees until 308 degree days (DD), base 50°F, have accumulated from McIntosh petal fall. Some regions are about half way there, or will be near 150 DD by this weekend. We expect PC pressure to continue and activity may be extended if temperatures remain cool; e.g., damage could continue into late June if it remains cool or could explode if we have a few nights of hot weather. The cooler temperatures mean that we need to remain vigilant and to continue to scout for injury. In some cool years fresh PC injury on fruit has been seen as late as mid-July.
Codling moth
Codling moth (CM) flights have been documented on several occasions over the last few weeks and a biofix has been set for some locations. Biofix is marked by a significant biological event, or first sustained flight, where moths are captured multiple days in a row or exceed a threshold of five moths per trap per week. Multiple biofixes can be set for each generation, and can vary by block, especially if trap captures do not consistently exceed threshold. Once a biofix date is established start tracking degree days, base 50°F, to time the first insecticide application. Continue to monitor traps weekly and be aware of a larger flight that may be more sustained and widespread than earlier flights.
The total population for each generation emerges in a shape of a bell curve over a 600 to 900 degree-day period, where we typically have 1000 DD between each generation of a biofix. This suggests that after 250 DD from biofix, only a small portion of the total population has emerged, i.e., 3% hatch. Orchards with high pressure or a large first flight, e.g., more than 10 moths per week, often apply the first larvacide at this time. If the initial flight is light or inconsistent due to cooler temperatures or rain a stronger flight can occur after the first biofix, e.g., two-weeks later. If this occurs the first larvicide can be applied at 350 DD. At 350 DD from biofix, 15% of larvae have hatched and at 450-550 DD up to 50% larvae hatch. If five moths are captured over the extent of the orchard, there is no need to apply a larvicide. If one or two traps exceed threshold, it is recommended to apply a larvicide to the entire area.
Note: Codling moth fly between 6-11 PM and will not fly when wind is in excess of 3 MPH, temperatures are below 60°F or if it is raining. Assign the biofix date for the warmest, calmest night. When checking traps, fluttering CM had likely flown within the last 48 hours. Most female CM can live for seven to 14 days, yet will mate and deposit the majority of eggs on the evening they emerge.
Treatment options include: applying a larvicide, e.g., Delegate (spinetoram), Entrust (spinosad), at 250 DD, base 50°F, from biofix; granulosis virus (Cyd-X) at 200-250 DD; or an ovicide, e.g., Rimon (novaluron), Esteem (pyriproxyfen), at 50-150 DD; see product descriptions below.
– Esteem is an insect-growth regulator and is typically used to manage San Jose scale (SJS) when applied pre-pink for eggs and in early to mid-June for crawlers. Esteem may offer some utility where CM numbers are drawn out, and may not reach a defined peak; and when an insecticide is also needed to treat SJS crawlers later in June. We typically receive 10 – 14 days of control from a larvacide, however an insect-growth regulator that affects eggs needs to applied every seven days or seven days after the larvacide to target the next hatch. Esteem does not seem to impact beneficials and other non-target insects.
– Entrust is an OMRI approved group 5 insecticide (spinosyns) that is in the same class as Delegate. Many organic growers have used Entrust for codling moth control in combination with mating disruption and CM granulosis virus. Entrust and Delegate may have a negative impact on the biological controls for woolly apple aphid (WAA) and may lead to more WAA issues later in the season. One option to reduce the impact is to use Delegate/Entrust for second-generation CM sprays.
– Exirel (cyantraniliprole) is a group 28 insecticide (diamides) that is in the same class as Altacor (chlorantraniliprole) and could be used for CM and extended PC management. Exirel may not be needed if CM populations are low enough and using an insect-growth regulator to control eggs. Exirel is also labeled for apple maggot.
– Mating disruption: It is not too late to apply mating disruption, or increase emitter density. Organic and IPM growers are encouraged to use mating disruption and the current weather forecast makes a good argument for its utility especially if the first generation flight is extended.
 
Note on Movento
Movento (spirotetramat) needs to be applied in late spring to early summer when shoots are actively growing and before terminals set. Exact timing and need for reapplication may vary by pest. Movento is fully rainfast after two hours and is fully systemic within one to two weeks after application (timing varies on environmental conditions and tree growth). Movento must be tank mixed with a spray adjuvant having spreading and penetrating properties, e.g., LI 700, to maximize leaf uptake and systemic activity of the active ingredient.
San Jose scale
Monitoring for San Jose scale (SJS) crawlers should begin across the region. Monitor known hotspots with black electrical tape applied to infested scaffold branches. With adhesive side towards tree, wipe a thin layer of petroleum jelly on the outside of the tape. If populations are high, concentrate a few traps in areas with greatest pressure. Increasing the number of monitoring sites may help eliminate false negatives. Low trap captures do not reflect overall pressure, i.e., false negatives. Low trap captures may indicate the beginning of the hatch. First generation SJS hatches over a narrow period, while second generation hatches over a wide period. Catches of 10-15 crawlers in a couple of days or 10 crawlers on one tape with zero on all other tapes, may warrant application. When scouting for SJS look for parasitization which can be seen as a visible hole in their waxy shell.
Spring lepidoptera
We are seeing a wide range of larval stages of green fruitworm, obliquebanded leafroller and redbanded leafroller. Now is about the time when many growers see the terminal injury and large larva. Generally by the time these larva are over an inch long, they are nearly done feeding and may not ingest enough insecticide to be managed effectively. Continue to scout newly planted trees, since they can bring overwintering larvae from the nursery that can be at a different growth stage than those in the rest of the orchard.
Leafhoppers
White apple leafhopper (WALH) and potato leafhopper (PLH) may begin to show up in orchards. Both species can reproduce within the orchard, however injury and species look different. White apple leafhopper are white and will move sideways across the leaf surface. Injury to the plant appears as white speckling on the top. These do overwinter in the upper Midwest and populations are often reoccurring in orchards. Potato leafhopper do not overwinter here and often are carried in on heat thermals and warm southern winds. We have begun to see some adults in orchards and have not seen any nymphs. Potato leafhopper populations begin to increase after the 1st or 2nd cutting of hay/alfalfa each year; second cutting is when we typically get a large influx. Nymphs can cause economic injury to young orchards by stunting terminal growth and inducing some stress. One or two nymphs per leaf cause leaf curling if allowed to feed for a prolonged period of time, e.g., four to seven days. Generally large semi-dwarfs, e.g., M.7, M.111, are not impacted by populations of PLH.
 
Flower thrips
Flower thrips are carried in on southerly breezes from the south. Scout terminals and shoots for leaf curl, resulting from feeding. The damage is most prevalent on the midrib of the leaf. Brown, feeding scars will be present on the underside of leaves and may be of concern on young or non-bearing trees. Thrips will continue to feed until terminals have set and are often not a concern on mature trees. Entrust and Delegate are both labeled for thrips. An organic grower applied Entrust (plus Biolink spreader sticker) directly to the terminals of his first and second-leaf trees with a backpack sprayer and received good control when comparing infestation to third and sixth leaf trees that did not receive treatment.
Grower comments on thinning
John compared thinning notes from two growers. The general thinning guides by variety for these growers are: Gala, not easy to thin and prone to small fruit; Honeycrisp, are also not easy to thin and more cautious about over thinning; and to not over thin McIntosh or Cortland due to the risk of having a lot of large apples that might not be marketable. Grower 1 applied NAA (e.g., Fruitone) + carbaryl at petal fall and has been using the carbohydrate model from the NEWA website. They had to apply a second thinning application with 6-BA (e.g., MaxCel). Grower 2 did not apply 6-BA this year due to cool temperatures, instead they are using more NAA + carbaryl or using NAA without carbaryl but adding Regulaid. Good thinning results have been achieved with NAA + Regulaid. 6-BA is not very effective when the temp is below 68°F.
The thinning window is closing, even with mild temperatures. In southern WI, this may be the last opportunity to thin. The carbohydrate model suggests that two weeks ago trees were under stress, but are now no longer stressed and in a positive range and even greater by mid-week.
