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Looking Ahead

Forages & Grains





Nursery & Forest

Degree Days

Volume 62 Number 18 Date 08/31/2017

CODLING MOTH - Moderate flights continued in a few southern orchard locations in the past week, but numbers have declined at most sites. The largest captures of 9-20 moths per trap were reported from Iowa, Racine and Waukesha counties. Apple growers are reminded that evaluating second-generation larval damage by early September will help to anticipate first-generation codling moth pressure next season. Orchards that have recorded captures higher than 10 moths per trap per week since the second flight began in July will likely find visible fruit damage at harvest, if the pest population is established in the orchard. If no damage is observed this fall or less than 1% of fruits are affected, then the source of the moths may be from outside of the orchard.

APPLE MAGGOT - Flies are expected to persist in orchards for several more weeks, or until about 2,800 degree days (modified base 50F) have been reached. The base 50F accumulation as of August 30 was 2,377 at La Crosse, 2,290 at Madison, 2,181 at Racine, and 2,067 near Green Bay. Apple maggot pressure has been variable but generally low this season. Continued maintenance of red sphere traps is recommended through September.

BROWN MARMORATED STINK BUG - Fruit growers and homeowners are advised to watch for this pest as the bugs swarm during warm fall days in search of overwintering sites. The brown marmorated stink bug is established in Brown, Dane, Door and Rock counties, and likely in other portions of southern and eastern Wisconsin. Nymphs and adults usually remain active through October or early November. Any swarms of stink bugs noticed this fall should be reported to DATCP at 1-866-440-7523.

YELLOWJACKETS - Significant numbers of yellowjackets could soon begin damaging grapes in many of the state's vineyards. Grape clusters should be promptly harvested as they ripen to discourage yellowjacket feeding. Basic sanitation practices such as removing overripe or damaged fruit are also useful. Commercially available traps can help to reduce numbers and the population buildup that often occurs by late August, but these traps must be deployed early in the season. Insecticides are not effective in managing yellowjackets in vineyards.

SPOTTED TENTIFORM LEAFMINER - The third and last flight of the season has declined in most orchards. A few sites in Iowa, Marquette and Racine counties reported higher counts of 405-915 moths from August 24-31, but captures at all other sites were below 139 moths per trap, which is relatively low for this pest. Moth flights should subside by mid-September.

SPOTTED WING DROSOPHILA - This invasive fruit pest will remain a serious threat to ripening fruit as the fall raspberry season continues, making it important for berry growers to maintain 5-day spray intervals as soon as first berry color change begins. Recent UMN studies have found that sprays applied in the early evening (1.5 hours before or after sunset) are most effective since peak SWD fly activity in raspberry crops occurs between 6:00 and 10:00 pm. Insecticide rotation is necessary for preventing SWD resistance development if short-interval sprays are being used, and pre-harvest interval (PHI) must be followed. Clean and timely harvests are also especially critical for SWD control. Dropped berries left on the orchard floor permit buildup and re-infestation, with as many as 20 flies emerging from a single fallen raspberry. Daily harvests are required and workers should be careful to harvest all mature raspberries available that day. Cooling fruit to 34-38F immediately after harvest is advised if the berries are not being delivered to markets the same day. A summary of research updates and control recommendations for open-field berry producers can be found on the UMN FruitEdge SWD website: https://www.fruitedge.umn.edu/82317swd.

-- Krista Hamilton, DATCP Entomologist