Pests & Diseases

Potato leafhoppers are active and alfalfa should be scouted for these insects capable of inflicting economic losses to stands, reports Mike Gray, University of Illinois Extension entomologist.

Alfalfa weevil
Larval populations of alfalfa weevil have been gradually increasing in first crop alfalfa. The WDATCP Wisconsin Pest Bulletin reported recently their surveys in south-central and central Wisconsin counties yielded an average of 3 larvae per 25 sweeps in 46 fields scouted.

In the mad rush to finish up what has been a challenging corn planting season, speed often takes priority over attention to detail, said Robert Bellm, University of Illinois Extension crop systems educator.

Insect development has been delayed in Nebraska due to below average temperatures; however, with temperatures climbing and alfalfa greening up, it is time to begin scouting for alfalfa weevils and the accompanying feeding damage.

Temperatures and conditions in southern Nebraska indicate that some feeding may be visible as tiny pinholes on the leaves of the upper part of the stem.

I reported recently on stunted and yellow alfalfa plants that were being reported in Berks, Dauphin and Lancaster counties (see pictures).

Samples were sent to Dr. Deborah Samac, USDA-ARS alfalfa pathologist, in St Paul, Minnesota, and I received back a report that the culprit is "Candidatus Phytoplasma asteris" or more commonly known as “Witches-broom phytoplasma.”

This key is designed to serve as a guide to identification of the more typical larvae of some of the common insect species found in many alfalfa fields during the mid-to-late season. A 10-power to 15-power hand lens will be most helpful in using this key.