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Looking Ahead
Volume 64 Number 16 Date 08/15/2019 CORN ROOTWORM - Preliminary results of the annual beetle survey indicate adult rootworm populations are low. The current state average based on sampling of 165 grain corn fields is 0.2 beetles per plant, with 66% of fields having no detectable population. The survey includes 229 cornfields and is expected to be complete by August 23. LILY LEAF BEETLE - Price County has been added to the list of Wisconsin counties with confirmed populations of the invasive lily leaf beetle (LLB). According to a resident's report, the beetles were observed on Turk's-cap lilies near Catawba on August 10. The addition of Price County brings the total number of infested Wisconsin counties to 11. Lily leaf beetle was also detected in Dane and Door counties two weeks ago. SOYBEAN APHID - Densities remain very low. Although a few soybean fields have developed populations of 30-40 aphids per plant in the past two weeks, most contain fewer than 10 per plant. Final aphid treatments, if required, must be applied before the R5.5 (mid-seed) growth stage to provide any economic benefit. WESTERN BEAN CUTWORM - Trap counts have decreased markedly, signaling the end of the moth flight period. A total of 368 moths were captured this week, compared to 1,619 last week. The cumulative state count as of August 15 is 3,422 moths in 57 traps, or an average of 60 per trap. Results of the 2019 trapping survey are summarized in the map on page 129. EUROPEAN CORN BORER - Summer moth emergence has peaked across the southern two-thirds of the state. Larval development is variable at this time, with 1st to 4th-instar caterpillars observed from August 8-14. Controls directed against second-generation larvae must be applied during the period after egg hatch and before the caterpillars bore into corn stalks and ears, prior to the accumulation of 2,100 degree days (modified base 50°F). The treatment window for second-generation larvae will close by August 22 in southern Wisconsin. CORN EARWORM - Significant flights of 21-80 moths per trap were registered in Dodge and Fond du Lac counties, with 130 moths captured at 5 of 16 pheromone trap locations this week. A cumulative total of 524 moths have been collected since migrants began arriving in mid-July. Although the corn earworm flights recorded over the last five weeks have not been especially large, fresh-market sweet corn growers should continue to monitor silking sweet corn fields and follow CEW flight reports through early September. -- Krista Hamilton, DATCP Entomologist 
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