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Looking Ahead
Volume 65 Number 4 Date 05/21/2020 BLACK CUTWORM - The annual migration intensified May 14-20 with the capture of 445 moths in 44 traps, the largest weekly count since moths began arriving in April. Larvae produced by moths of the spring flight are in the early instar stages and signs of their feeding such as small pinholes in the leaves should be detectable next week in emerging cornfields. Based on the 10-day temperature forecast, the primary damage period is expected to begin by May 26 in far southern Wisconsin. ALFALFA WEEVIL - Adults have become more common in alfalfa and spring egg deposition is increasing. Surveys to assess larval populations and defoliation levels should begin next week (May 24-30). EUROPEAN CORN BORER - Degree day accumulations at advanced locations such as Beloit and Platteville will surpass the 374 heat units (modified base 50°F) required for corn borer moth emergence by May 26. In 2018 and 2019, the first corn borer moths were collected in black light traps by May 30 and June 5, respectively. Overwintered larvae in the central and northern areas are just now entering the pupal stage, and the earliest spring moths are anticipated there June 1-7. PLUM CURCULIO - Beetle migration into the orchard perimeter is beginning. Apple growers who have experienced past problems with this pest should begin checking early-sizing cultivars such as Ginger Gold, Ida Red and Liberty for crescent-shaped oviposition scars. The minimum size of fruitlets preferred for egg laying is 5 mm. Applications are not effective until fruit damage is observed. POTATO LEAFHOPPER - Migrants were collected in low numbers on May 19-20 from alfalfa fields in Grant, Iowa and Lafayette counties. Their recent appearance confirms that the first distinct migration event of 2020 has occurred. CODLING MOTH - Evening temperatures will be appropriate for moth flight over the weekend of May 23-24 and throughout the week ahead. Close monitoring of pheromone traps is suggested for southern and central Wisconsin orchards until the biofix is documented. Conditions required for codling moth flight are wind speeds between 3-5 miles per hour when temperatures are above 62°F without rain. If temperature fluctuations lead to inconsistent moth activity, the biofix date should be assigned to the warmest, calmest night. -- Krista Hamilton, DATCP Entomologist 
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