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Monday, April 8, 2019

Alfalfa Weevil Pressing Early Area Hay Development

Alfalfa Weevil Pressing Early Hay Development

               There are not many large-scale production alfalfa fields in Hale, Swisher, & Floyd any longer, but there is a notable amount.  These fields are usually near deeper irrigation water or with focused irrigation efforts where the economics of the situation dictate a specialty, high-quality hay crop for a diverse local livestock market or personal livestock feeding needs.  The dotting of these 30 to 100-acre fields in the area are easy to miss on the grand scene, but the economic importance to those producers and their livestock customer base is undeniable.  The Plains Pest Management Scouting Program makes solid efforts to include at least one of these fields annually to help keep tabs on this small but critical area crop.  Article releases regarding alfalfa have been few as the scouting season ranges from February through to November with early spring being the key management timing.  That is unless there is a widespread issue.
Proper use of a sweep net is universal and very helpful for in alfalfa scouting.
Scanning the sweep net after 20 sweeps will tell you how many weevils and weevil larva are in field

               This week we found an economic population of alfalfa weevils.  For all specific and recommended alfalfa pest management and pest control practices please refer to our Texas A&M AgriLife forage management guide.  I vastly prefer to utilize the sweep net method for checking alfalfa, checking two stems at every point I take twenty sweeps as I move across the field.  Using this method, the ET for weevils are 7-14 per twenty sweeps on vegetative alfalfa and 20 per 20 sweeps on blooming alfalfa with associated leaf damage or skeletonizing from weevil feeding.  For our program field near Tulia, this week I averaged 8 young weevil larva per twenty sweeps with the ample associated leaf damage on mid-vegetative growth alfalfa.  Along with this population I found two aphid species, which could cause issues later but were not pressing at this time.  I have word of other area fields where both pests were an issue.  Products labeled for alfalfa weevil or aphids in alfalfa are limited and I earnestly suggest prompt field scouting, consulting an area entomologist, and giving our guide a look if you feel you may have issues in your alfalfa this week.

Alfalfa weevil feeding on alfalfa.

Blayne Reed