Volume 58 Number 18 Date 11/21/2013
SPOTTED WING DROSOPHILA - Significant losses to the fall raspberry crop were reported for the second year in a row. The first adults of the season were collected by UW researchers in Vernon County on June 24 and many new cases of larval infestations in fruits appeared rapidly across the state in the following month. By mid-September, spotted wing drosophila (SWD) had been confirmed in 23 counties, from Racine in the southeast to Bayfield in the far north. Two additional cases were documented in October for total of 25 counties in 2013. The early and rapid emergence of flies and larvae this year suggests this invasive pest is established and overwintering locally in Wisconsin.
APPLE MAGGOT - The first flies of the season were registered from July 4-10. Counts remained low until early August when activity surged abruptly and numbers increased to 15-25 flies per trap in a few southern apple orchards. Emergence peaked by mid-August then declined rapidly with the intensifying drought. Dry weather in July and August and timely insecticide applications generally suppressed the flies and their damage this year.
APPLE SCAB - Spring weather conditions were highly suitable for scab development in 2013. Cool temperatures and frequent rainfall during the primary infection period delayed cover sprays and diluted fungicides, making control difficult. The cooperator near Deerfield in Dane County noted that scab pressure was the highest in many years, although most growers indicated their disease management programs were effective.
EXOTIC GRAPE MOTHS - Seventeen vineyards in Brown, Calumet, Dane, Door, Fond du Lac, Kewaunee, Manitowoc, Sheboygan and Waushara counties were systematically trapped for exotic grape moths by DATCP entomologists between May 1 and September 30. The target pests were the light brown apple moth, European grape berry moth, European grapevine moth, and silver Y moth, all insects of high concern to the grape industry and USDA APHIS "priority pests" for grapes. No exotic fruit moths were found.
STINK BUG - A fruit grower in Trempealeau County reported that these insects were the primary cause of surface damage to apples and peaches in her orchard this season. Feeding and probing by the nymphs and adults prior to harvest left depressions on the fruits that appeared only after a period of time in storage. The aesthetic damage was attributed to native species of stink bug and not the invasive brown marmorated stink bug, which has yet to turn up in any Wisconsin orchard or agronomic crop.
CODLING MOTH - Moths began appearing in traps on the night of May 19 and the biofix was set from May 21-22 in southern orchards and from May 28-June 1 at central and western sites. The first flight peaked in the southern half of the state by late June, although spring moths persisted well into July. Summer moths appeared from mid- to late July and controls were applied during the first two weeks of August. Counts stayed comparatively high until early September. By most accounts, emergence of the first generation was fairly predictable this spring, resulting in adequate early-season control and fewer problems with the second larval generation.
WHITE-LINED SPHINX MOTH - This insect was unusually abundant this season. The larvae were noted on apple, evening primrose, rose and grape in July and adults of the summer flight were very active from August through early October. Reports suggested the largest populations occurred in central and west-central Wisconsin.
DOWNY MILDEW OF GRAPE - Many vineyards were adversely impacted by downy mildew and anthracnose this year due to favorable weather conditions for disease development, according to a report from the UW-Madison Plant Disease Diagnostic Clinic. Removal of leaf litter on the vineyard floor and selective pruning were recommended to reduce the amount of overwintering inoculum.
-- Krista Hamilton, DATCP Entomologist