Volume 62 Number 11 Date 07/13/2017
APPLE MAGGOT - Emergence of flies continued for the second week, with a high count of 5 flies on red sphere traps reported from Grant and Sheboygan counties. Captures have also occurred in Bayfield, Dane, Fond du Lac, Marathon, Pierce, and Racine counties. Apple orchards affected by recent hailstorms are at increased risk of infestation by this pest since hail-damaged fruits release volatiles that can attract flies from long distances. Maintenance of traps will be important as emergence continues and oviposition on apples increases in late July and early August.
CODLING MOTH - Counts have decreased in most orchards as the first flight subsides. Orchardists who have not observed a distinct decline in moth activity and are having difficulty determining the most effective treatment window should use an accumulation of 1,000 degree days (modified base 50°F) from the spring biofix in late May to time the start of larvicide applications. As a general rule, approximately 1,000 degree days are required between the first and second larval generations.
SPOTTED TENTIFORM LEAFMINER - The second flight should peak soon at most monitoring sites, although counts remain high. Six of 21 orchards reported counts above 500 moths per trap this week, with the high count of 1,377 moths per trap registered in Marquette County. Egg laying is expected to be heavy as long as pheromone traps continue to register high numbers of moths. Apple orchards with populations greater than one mine per leaf or a history of infestation should consider controlling second-generation larvae to reduce build-up of leafminers before the third flight begins in late July or August.
POTATO LEAFHOPPER - A Fond du Lac County apple grower reports that populations are heavy in some orchard blocks and that associated discoloration of new shoots and mild hopperburn symptoms are appearing. Leafhoppers have also become abundant in western Wisconsin orchards. One- to two-year-old, non-bearing apple trees are most susceptible to leafhopper feeding and should be monitored for leaf curling and yellowing caused by the adults and nymphs. Treatment is justified at levels of one or more nymphs per leaf when symptoms are evident.
-- Krista Hamilton, DATCP Entomologist