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Extension Entomology

Tag: treatment thresholds

Alfalfa Update

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

 

Potato leafhoppers are still common in all alfalfa fields sampled in the last 7-10 days, unless they have been swathed during that period of time.  Fields swathed within the last week did not have enough potato leafhoppers to reach a treatment threshold.  However, fields swathed just 10-14 days earlier are once again loaded with these little lime green, wedge-shaped leafhoppers.

There do seem to be good populations of green lacewings in uncut alfalfa fields.  However, they do not appear to be impacting the potato leafhopper populations.  We did pick up one alfalfa weevil larva and one adult in an uncut alfalfa field but the alfalfa weevils should not be of concern as major defoliators until next spring.

 

 

Alfalfa Update

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Swathing seems to have interrupted the potato leafhopper increases that were seen prior to cutting.  All the fields sampled prior to swathing in north central Kansas exceeded the treatment thresholds.  Conversely, all the fields sampled post-swathing had potato leafhopper population well below economic injury levels, i.e. 20 potato leafhoppers per 20 sweeps pre-swathing vs. two per 20 sweeps post-swathing.  Continued monitoring would be prudent as these pests may stray around until October and continue to produce offspring.

 

Spotted alfalfa aphids are still present in alfalfa fields but at relatively insignificant infestation levels.  These aphids seem to do very well in mid-summer’s hot, dry conditions but usually don’t reach densities heavy enough to cause yield-reducing stress.

spotted alfalfa aphid

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