The following information is an update on alfalfa pest activity from K-State Entomology.
Samples were taken from alfalfa fields in north central Kansas on April 11th. Despite the recent cold weather and lack of measurable moisture, the alfalfa did not show obvious signs of stress and had even grown a little since the April 4-5 when the fields were last checked.
Alfalfa weevil
The recent cold temperatures apparently took a toll on some of the small alfalfa weevil larvae. However, it did not kill them all as live larvae of different sizes was found still feeding in terminals and often live ones feeding right beside dead ones (see photos below; all photos taken by Holly Davis, K-State Research and Extension).
No case with more than a 5% infestation was found. In addition, no adults or larvae were found in the leaf litter below the canopy. So, apparently, the recent record cold temperatures killed 40-50% of the small alfalfa weevil larvae that had started feeding. It remains to be seen how many eggs are still to hatch, but so far infestation levels we have noted are not anywhere near treatment thresholds.
Other pests
Pea aphids were also noted as were parasitized pea aphids (mummies). Lady beetles were also active.
For management decisions relative to alfalfa pests, please see the Alfalfa Insect Management Guide, available at: https://www.bookstore.ksre.ksu.edu/pubs/mf809.pdf
Jeff Whitworth, Extension Entomologist
jwhitwor@ksu.edu
Holly Davis, Entomology Research Associate
holly3@ksu.edu
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