Volume 52 Number 8 Date 06/15/2017
APPLE MAGGOT - Emergence of flies from the soil could begin by June 16 near Janesville, June 20 near Eau Claire and June 25 near Appleton This annual event corresponds with the accumulation of 900 degree days (modified base 50°F) when soil moisture is adequate. Traps should be placed next week in perimeter trees adjacent to abandoned orchards or woodlots to capture the earliest flies.
OBLIQUEBANDED LEAFROLLER - Larvae resulting from the first moth flight are emerging across the southern half of the state. The small, newly-hatched caterpillars are controlled by most products applied for codling moth (except granulosis virus and mating disruption), but scouting is still required to determine if codling moth sprays have effectively reduced OBLR populations or if additional measures are needed to prevent fruit damage. Sampling for fruit and foliar feeding should begin seven days after the first moths are captured in pheromone traps.
ROSE CHAFER - This generalist pest is emerging in greater numbers and may rapidly arrive in vineyards and orchards, where the beetle skeletonize leaves and consume developing fruit clusters. Scouting twice weekly is advised for vineyards on sandy soils and those with a history of rose chafer problems once the first beetle is observed. An average of two beetles per vine has been suggested as the basis for initiating controls. Systemic soil drench insecticides are only effective if applied at least 20 days in advance of the adult emergence period. Commercially available traps can attract more beetles from surrounding areas and are not recommended for use in vineyards.
LESSER PEACHTREE BORER - Counts ranging as high as 57 moths per trap per week indicate the first of two flights should soon peak. Control of LPTB in orchards is based on preventing larval establishment underneath the bark and should be timed just before or to coincide with egg hatch. Once the larvae are under the bark, chemical control is ineffective. LPTB egg hatch begins about 8-10 days after moth emergence, thus the optimal treatment window is 7-14 days after the first moths are captured in pheromone traps. Directed sprays must be applied uniformly to drench the trunk and scaffold limbs to a height of about eight feet.
Orchards that record high LPTB trap counts are advised to begin checking for signs of infestation in the gum in cankered areas, such as presence of pupal skins, sawdust, and frass produced by feeding borers. If the gum does not contain frass or sawdust, the injury is probably not caused by borers. LPTB problems are almost always associated with Cytospora canker and, to a lesser extent, pruning wounds, winter injury, and mechanical damage. A second and more damaging flight occurs in late August or September.
REDBANDED LEAFROLLER - Moth counts are expected to increase by July as the second flight gains momentum. Minimal RBLR activity was noted again this week, with average counts varying from 0-20 moths per trap and averaging less than three per trap.
SAN JOSE SCALE - Monitoring for crawlers by taping scaffold branches should be underway. Concentrating the tape on younger limbs (2-3 inches in diameter) in blocks with a history of SJS damage is advised. A 10x hand lens is required to view the oval, bright-yellow crawlers. According to Orchard IPM Specialist John Aue, captures of 10-15 crawlers in a few days or 10 crawlers on one tape with zero on all other tapes, may warrant application.
SPOTTED WING DROSOPHILA - The UW reports that emergence of SWD flies began by June 5 in Dane County. Flies have also been captured in survey traps in Door and La Crosse counties as of June 15. Berry growers should intensify monitoring and scouting efforts at this time, and plan to implement SWD treatment programs once the first flies are captured.
-- Krista Hamilton, DATCP Entomologist