June 19, AppleTalk Conference Call

AppleTalk Conference Call Summary
Tuesday, June 19, 2018, 8:00 – 9:00 AM
Guest speaker: Krista Hamilton, Entomologist – Bureau of Plant Industry/Division of Agricultural Resource Management, Wisconsin Department of Agriculture, Trade and Consumer Protection
Presenter: John Aue, Threshold IPM
Moderator: Peter Werts, IPM Institute of North America; questions or comments, pwerts@ipminstitute.org

June 19th Call Stream: CLICK HERE

Codling moth

For the last two weeks, many orchards experienced unusually low trap captures. Now, the codling moth flight seems to be picking up. Most growers in the region have accumulated 400-500 degree days (DD), base 50°F, since biofix. The population model predicts that once we reach 500 DD from biofix, 50% of first generation eggs will have hatched. The flight tends to drop off around 600 DD from biofix, as most of the moths have already emerged. However, atypical flight patterns this season leave predictions up in the air. Growers are advised to stay up to date on degree-day accumulations by checking data from their on-farm weather stations or the nearest NEWA station regularly. Note: Adult moths can live for seven to ten days before dying.

The insecticides we use to manage codling moth, while somewhat rainfast, will not be able to withstand more than two inches of rain. Even the old organophosphate, Imidan (phosmet), which still offers control after 90% wash-off due to its high toxicity, will require reapplication when two inches of rain fall on a seven-day-old application. If wash-off occurs, review trap captures at 150-250 degree-days prior to the rain event to determine if a reapplication is warranted. Recently hatched codling moth larvae, while very small, do not drown during the severe rain events we have been experiencing, and any flight that exceeded threshold between 200-250 degree-days prior to the rain will require reapplication.

If weekly codling moth trap counts are 5-15/week, there is some flexibility on when to reapply an insecticide for hatching larvae. Captures exceeding 40-60/week are dangerous levels and doesn’t offer much flexibility in timing an insecticide. A threshold of 5/week is unlikely to result in any noticeable crop injury.

Not all adjuvants are capable of improving insecticide rainfastness. Adjuvants that are surfactants allow sprays to seep deeper into a plant’s nooks and crannies but do not improve the pesticides’ rainfastness. Other adjuvants that don’t promote rainfastness are buffers or water conditioners that ensure the proper degree of acidity, and penetrants or activators like LI 700 or Regulaid that help systemic pesticides, e.g., neonicotinoids or Movento (spirotetramat), or plant-growth regulators to enter the leaf cuticle.

Adjuvants advertised as “stickers” like Nu Film P or Nu Film 17 may help improve rainfastness by creating a physical barrier over the surface of the pesticide. This prevents weathering of the pesticide by wash-off and ultra-violet oxidation, since pesticides degrade from exposure by both rain and oxidation from ultra-violet rays. A sticker can be applied when rain is forecasted soon after a larvicide application. Stickers have a wide application range for different intended effects, but John recommends a median rate when using sticker-type materials. Find more information on spray adjuvants from the Penn State Extension here, https://extension.psu.edu/spray-adjuvants.

Maintaining a cover of a codling moth larvacide, when rains are frequent support the benefits of using mating disruption. Even if a full rate of mating disruption is not used, a low rate of mating disruption would offer some suppression of codling moth under these current conditions.Table 1. Adapted from ‘Rainfast characteristics of insecticides on fruit’ posted on June 7th, 2018 by John Wise, http://msue.anr.msu.edu/news/rainfast_characteristics_of_insecticides_on_fruit.

Lesser appleworm

Orchards should all have at least one lesser appleworm (LAW) or oriental fruit moth (OFM) trap in their orchards. We have yet to catch any OFM this year, and rarely do, but are consistently catching LAW in our OFM traps. There is not established threshold for LAW, a nominal threshold of 10 has been set by John to indicate when populations are high enough to warrant treatment. If a grower is catching 15-20 LAWs in a week, then there is likely a population that will need to be managed. The injury from LAW is indistinguishable from codling moth. Growers using mating disruption should watch LAW or OFM trap counts. Lesser appleworm has nearly the same exact timing of their lifecycle, and insecticides applied for codling moth will manage LAW populations. Oriental fruit moth has three generations per year and their life cycle does not align with codling moth.

Brown marmorated stink bug – summary on status in Wisconsin by Krista Hamilton

This invasive pest from Asia was first documented in Allentown, Pennsylvania in 1996. By 2005, brown marmorated stink bug (BMSB) was also reported in the San Francisco area. BMSB began to receive attention in 2010 when it first began to cause catastrophic damage to fruit and vegetable crops in the Mid-Atlantic States, growers reporting up to 50% losses in some places. The insect was also documented for the first time in WI in the same year. There were 18 confirmed BMSB cases between 2010 and 2014, and 35 reports in 2015 alone. By 2015, BMSB was established in Dane County and was likely present in other south-central locations as well.

In 2016, the Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP), IPM Institute and UW Entomology developed the first official trapping survey to collect baseline data and identify emerging problems. 51 traps were set with one-to-four per orchards. One trap was set in each of the following areas: woods, urban, apples and other crops, like pumpkins. Seven of 51 traps caught BMSB, six of which were in Dane County and one was in Rock County. One trap caught as high as 42 BSMB. The total number of captures between July 23 and November 4 was 185 in the seven traps. Note: No BMSB nymphs were captured in 2016.

2017’s survey was set up similarly with 38 traps set at 14 sites, and captures were counted between June 17 and November 10. 152 nymphs and 200 adults were caught on 13 traps at seven of the sites – one in Door County, four in Dane County, one in Outagamie County, and one in Rock County. One BMSB was caught near Sturgeon Bay in July, and the highest individual count was 61 specimens in a Dane County trap. By 2018, overwintering populations were found in southeast orchards as early as May 24. Second-instar nymphs were captured in Madison as of June 12. The 2018 survey was expanded to approximately 106 traps at 53 sites, and all DATCP cooperators began monitoring BMSB traps while the IPM institute checked 23 orchards and vineyards. All orchards switched to using clear sticky panel traps with dual-lure pheromones for BSMB and native-green stink bug.Currently, BMSB has been confirmed in 22 of Wisconsin’s 72 counties, and is established in at least 9 counties, including Brown, Dane, Jefferson, Milwaukee, Outagamie, Rock, Walworth, Waukesha and Winnebago. Hotspots continue to be in the Madison, Milwaukee, Waukesha and Green Bay areas.

Reports from the western side of the state have been very few, but Minnesota data suggests BMSB pressure is increasing in Twin Cities and along the Minnesota-Wisconsin border.

Obliquebanded leafroller

Trap data should be used to begin scouting terminals at 10-14 days after peak flight. Look for feeding injury to terminals or small larvae. Since non-bearing trees are often managed differently, this is a good place to look for obliquebanded leafroller (OBLR). Larvacides applied for codling moth will manage OBLR and if not applied to non-bearing trees, larvae will likely be there feeding. If you see anything wrong with a tiny leaf that has just emerged, it could be an OBLR larva. Other insects causing terminal injury right now include potato leafhopper and thrips. The first OBLR instar is very difficult to see, even with a 10x hand lens. Even though there is no threshold based on trap captures. Trap catches are reflective of pressure e.g., five OBLR v. 50 OBLR, suggest significant pressure in the later.

San Jose scale

The first crawlers of the season were found on June 16 along the Illinois-Wisconsin border. Monitoring San Jose scale (SJS) crawlers should begin across the region. Monitor known hotspots with black electrical tape applied to suspect 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.

Summer fruit rots

Summer fruit rots, e.g., bitter rot, have become increasingly problematic in our region. Seasonal severity of fruit rots is dependent on weather conditions, i.e., heat, humidity, and level of overwintering inoculum. 2017 was a mild year for fruit rots, however, this year may be a much different scenario considering the amount of rain, heat and humidity so far. Honeycrisp is particularly susceptible to fruit rots. Patty McManus, Plant Pathology, UW-Madison, will be on a call later this summer to discuss summer fruit rots.