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Forages & Grains
Volume 58 Number 9 Date 06/27/2013 ALFALFA WEEVIL - Larvae populations are decreasing in second crop alfalfa. The average count in the last reporting period was very low at 0.03 per sweep and leaf feeding ranged from 5-10%. Damage is expected to subside by early July as the remaining third and fourth instar larvae enter the non-feeding pupal stage. PEA APHID - Counts of this insect have also declined with the rainy, humid weather. Surveys in Dane, Green, Iowa, Richland, Sauk and Vernon counties yielded only 1-3 per sweep and an average of less than one per sweep. The humid and wet conditions experienced in the last week favor several fungal pathogens that regulate aphid populations. POTATO LEAFHOPPER - Alfalfa surveyed in the south-central and southwest areas contained low to moderate counts of 0.1-1.6 per sweep. Circumstances have not justified treatment in any field surveyed as of June 26, but reproduction is occurring and populations are on the increase. Economic thresholds for this pest are as follows: 0.5 per sweep for 3- to 7-inch alfalfa, 1.0 per sweep for 8- to 11-inch alfalfa, and 2.0 per sweep for alfalfa 12 inches or taller. MEADOW SPITTLEBUG - The adult stage of this insect was swept from alfalfa in La Crosse and Monroe counties, signaling that the population has matured and spittle masses should not reappear until next spring. The highest number collected from second crop alfalfa in the past week was one per sweep. PLANT BUG - Surveys conducted in the southern half of the state are showing low populations of 0.1-1.7 per sweep. The economic threshold is five per sweep for mixed counts of adults and nymphs. Adults are more abundant than the nymphs in most fields. -- Krista Hamilton, DATCP Entomologist 
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