Kansas State University


Extension Entomology

Alfalfa Update – alfalfa weevil larvae, pea aphids, lady beetles

–by Dr Jeff Whitworth and Dr Holly Davis

Sampled alfalfa fields in north central Kansas on 11 April.  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 4th and 5th of April when we last checked these fields.  The recent cold temperatures apparently took a toll on some of the small alfalfa weevil larvae.  However, it did not kill them all as we found live larvae of different sizes still feeding in terminals and often live ones feeding right beside dead ones.



In no case did we find more than a 5% infestation.  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.



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




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