Volume 62 Number 18 Date 08/31/2017
CORN EARWORM - Migrants arrived in significant numbers for the second consecutive week at two monitoring locations, while counts at nine other sites were low. The pheromone traps at Arlington in Columbia County and Beaver Dam in Dodge County captured 156 and 129 moths, respectively, an increase from 111 and 16 moths recorded last week. The August 24-31 count of 351 moths brings the cumulative two-week total to 639 moths in 15 traps since the primary migration began. Sweet corn growers are advised to maintain corn earworm scouting and management programs as long as moth activity persists and green silks are available for oviposition.
FALL PESTS - Nuisance insects including the boxelder bug, brown marmorated stink bug, multicolored Asian lady beetle, and western conifer seedbug will begin aggregating on warm southern and western exposures of buildings later this month in advance of their indoor invasion. Exterior insecticide treatments may temporarily deter these insects from entering homes, but exclusion measures such as sealing cracks around windows, doors, siding and other openings are preferred. Insecticides should be only applied by a licensed pest control technician and considered for severe infestations. Fall nuisance insects do not reproduce inside the home or cause structural damage.
BROWN MARMORATED STINK BUG - This new invasive pest has been trapped in Dane, Door and Rock counties this summer, including a few south-central Wisconsin apple orchard locations. The UW Insect Diagnostic Lab also recently confirmed the identification of second-instar nymphs collected from raspberries in Waukesha County. Similar to the multicolored Asian lady beetle and boxelder bug, BMSB clusters on the exteriors of buildings in autumn in search of protected overwintering sites. Reports from Mid-Atlantic States where BMSB is a severe pest of fruit, field and vegetable crops indicate that BMSB usually develops from a household nuisance into a significant agricultural pest over a period of 5-10 years. To date, there has been no official confirmation of fruit or agronomic crop injury in Wisconsin, but this will likely change in 2018. Any swarms of stink bugs noticed this fall should be reported to the DATCP Pest Survey Program at 1-866-440-7523.
CORN ROOTWORM - Beetle pressure has been much lower than anticipated this season. The August survey found a pronounced decrease in the state average beetle count from 0.5 per plant in 2016 to 0.2 per plant in 2017, the lowest populations in the last 46 years. Although this summer's historically low adult rootworm levels indicate a generally lower threat of larval root damage to continuous corn next summer, survey data represent regional populations and not pressure in individual fields. Producers and consultants are advised to sample beetle populations once more by early September to inform next year's rootworm management decisions and/or planting rotation.
LATE BLIGHT - Development of this disease continues to be reported. The UW has confirmed several cases on tomato in Dane, Kenosha, Jefferson, Pierce and Waukesha counties as of August 31, as well as on potato in Iowa, Portage and Waushara counties. UW-Extension Vegetable Plant Pathologist Dr. Amanda Gevens is encouraging growers to submit symptomatic plants to her lab or the UW Plant Disease Diagnostic Clinic. Testing will provide late blight confirmation and pathogen genotyping to guide fungicide selection. Both the US-8 and US-23 genotypes have been detected in Wisconsin this season; the US-8 found in Portage and Waushara Counties and is Ridomil-resistant. Plants showing symptoms of late blight cannot be saved and should be disposed of in plastic bags to limit its spread.
-- Krista Hamilton, DATCP Entomologist