Volume 63 Number 13 Date 07/26/2018
STINK BUG - Surveys in field crops suggest that activity is escalating and stink bugs are likely to start invading orchards in greater numbers. Growers can begin inspecting fruits in the week ahead for dimples or dark, irregular circular depressions typical of stink bug feeding, and should flag sites with multiple depressions on the same fruit or tree. Damage is often limited to specific areas in the orchard and depending on the distribution of the population, spot treatment may be adequate.
APPLE MAGGOT - Captures of flies on red spheres and yellow sticky traps have increased at several sites, indicating adult emergence may have peaked in southern and central Wisconsin. The development model for AM predicts peak fly emergence for 1,600 degree days (base 50°F). The Milwaukee-Racine area should accumulate 1,600 GDD next week, while the areas north of Wausau can expect to reach this point during the second week of August. Heavy oviposition on apples is expected to continue for another 2-3 weeks.
JAPANESE BEETLE - Apple orchards in southern and western Wisconsin are reporting heavy beetle populations, with significant damage to foliage and the terminal ends of branches along orchard perimeters. If the beetles are causing unacceptable injury and treatment is required, growers can minimize insecticide use by spot treating only the most-infested varieties. Because sprayed trees can be reinvaded, infested orchard blocks should be inspected weekly as long as beetles are present. Never spray when bees are foraging.
WHITE APPLE LEAFHOPPER - Peak egg laying has occurred over much of the southern half of the state with the accumulation of 1,750 degree days (base 48°F), and second-generation eggs are beginning to hatch. Apple growers who observed damage caused by the first generation several weeks ago should scout for stippling and whitish spots on leaves in the interior of tree canopies. The summer nymphs feed well into September and can cause significant chlorophyll loss. Ordinarily, control should target first-generation nymphs, but if justified, treatments for the second generation are also effective.
CODLING MOTH - The second flight is well underway. Regular trap checks should continue in August to determine if the economic threshold of five moths per trap per week is exceeded. The need for treatment of the second larval generation is less consistent than with the first generation, and depends upon the success of spring CM controls and whether pressure is coming from wild trees outside the orchard. Spot treatment is usually an effective approach for managing second-generation larvae. The high count for the last reporting period was 20 moths in Racine County, where a significant flight was recorded overnight on July 19.
-- Krista Hamilton, DATCP Entomologist