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Forages & Grains
Volume 64 Number 19 Date 11/07/2019 ALFALFA PESTS POTATO LEAFHOPPER - Populations of this insect were the highest in many years, influenced by spring weather systems that brought large leafhopper migrations into the state. The monthly average count in 120 alfalfa fields sampled from July 1-31 was 2.04 per sweep, with above-threshold averages (>2.0 per sweep) recorded at 47% of sites. The abundance of leafhoppers carried over into other crops as second-crop hay was harvested, and damage to fruit trees, nursery plants, and vegetables was common in July and August. ALFALFA WEEVIL - Counts in first-crop alfalfa were low in 2019. The first appearance of larvae was delayed by below-normal spring temperatures and began in southern Wisconsin by May 22. Peak weevil feeding was predicted for June 16-29 across much of the state. Sweep net counts remained low (<1.0 per sweep) through late June, while leaf tip damage estimates did not exceed 20% in any surveyed field. The larval feeding window closed by early July without significant defoliation observed this year. -- Krista Hamilton, DATCP Entomologist INDUSTRIAL HEMP PESTS EURASIAN HEMP BORER - Moth emergence was first reported on May 26 in Walworth County and a peak in the spring flight was noted around June 9. Larval damage became evident by late June, when many hemp growers began noticing infestations in their fields. Reports of first-generation Eurasian hemp borer (EHB) damage were received by DATCP from July 1-14. A second flight started around July 18 and continued for several weeks. The lengthy second flight produced widespread infestations of second-generation larvae ranging from very mild to severe. Observations from fall hemp inspections indicate EHB pressure was highest in southern Wisconsin. Eurasian hemp borer was the most common and destructive hemp pest insect in the state in 2019. HEMP LEAF SPOT - Hemp foliage with distinct, round spots was diagnosed by the DATCP Plant Industry Laboratory with hemp leaf spot disease. The samples were collected from fields in Dane, Vernon and Waupaca counties. The Bipolaris-like fungal pathogen that causes hemp leaf spot has yet to receive an official name in the scientific literature. -- Anette Phibbs, DATCP Plant Pathologist 
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