The alfalfa crowd gathered at the Arizona Alfalfa and Forage Workshop held in March was quizzed by University of Arizona staff about their chemical use to control pests in alfalfa fields. Participants included growers, pest control advisors, members of the agricultural industry, and others.
When asked about how they decide when to use an insecticide to control the Egyptian alfalfa weevil (EAW), 37 percent said their decision was based on the threshold level, 29 percent did not treat with an insecticide, and 14 percent sprayed for the weevil when spraying for aphids.
When asked how many times per season they sprayed for EAW in the past two seasons, 39 percent said not at all while 36 percent said once.
On the question, which aphid species is most abundant in your alfalfa? About 41 percent said the blue alfalfa aphid was the most prevalent while 28 percent said the pea aphid, and 21 percent said the cowpea aphid.
When asked how they decide whether to chemically treat aphids in alfalfa, 41 percent said their decision is based on the remaining time until harvest. A UA note - when close to harvest time, growers may decide to cut alfalfa early as a strategy to mitigate alfalfa populations that are approaching threshold, instead of an insecticide treatment.
Which chemicals provided an acceptable level of aphid control? Of all the respondents, the top three products were Sivanto (22 percent), followed by Lorsban and Dimethoate tied at about 17 percent.
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