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Issue No. 3, Article 5/April 8, 2005

Getting Ready for Alfalfa Weevils

It's that time of year again. Not only has baseball season begun, but it's time to gear up for alfalfa weevils. There's little correlation between the two, I know. But these warm spring days are great for playing ball and development of alfalfa weevils. Here's a brief scouting report.

Larval hatch from eggs is expected to occur after the accumulation of 300 degree-days from January 1. Currently, alfalfa fields in southern Illinois have accumulated just over 200 degree-days and will soon be experiencing larval hatch (Figure 1). In fact, certain areas may already have alfalfa weevils feeding on new alfalfa growth. Some alfalfa fields may warm up sooner than others. For example, in fields that are on south-facing slopes or protected by timber or wooded areas, alfalfa weevils may develop sooner. In these situations, scouting should begin earlier than in other fields. One word of caution: clover leaf weevils can be present in alfalfa fields just before alfalfa weevils are noticed. Be sure to identify the weevil larvae that are present in the field before making any treatment decisions.

Figure 1. Accumulated degree-days (base 48°F) for alfalfa weevils, beginning January 1, 2005.

Growers across the state should brush up on scouting for alfalfa weevil larvae. More information on identification, life cycle, scouting, and management can be found on factsheets for alfalfa weevil (Adobe PDF) and clover leaf weevil (Adobe PDF). To get current degree-day accumulations for alfalfa weevils and other insect pests, visit our degree-day calculator.--Kelly Cook

Kelly Estes

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