- First alfalfa cutting may be earlier than usual.
- Watch for aphid infestations in drought conditions.
- Consider treatment thresholds for various aphid species.
Alfalfa has been under stress in many parts of Kansas during much of March and April. Drought, alfalfa weevil and various aphids are causing stunted growth and damaged leaves, said Jim Shroyer, Kansas State Research and Extension crop production specialist. This will affect management plans.
“Normally, the first cutting of alfalfa should be made when regrowth at the crown is apparent. In the spring, this occurs prior to bloom. But this year, the combination of drought and heavy insect pressure has stressed the dryland alfalfa,” Shroyer said.
Producers may have to consider taking their first cutting earlier than they’d like, he said, even if regrowth at the crown has not yet begun. Leaves contain more nutrients than stems, and it’s important to retain as many of the leaves as possible to produce high-quality forage, he explained.
“If producers need to make the first cutting before the optimum time, root reserves on newly-established stands or even older stands may not be satisfactory to permit rapid regrowth. But if the alfalfa is not cut, the hay crop may be lost and damage to the stand may occur,” Shroyer said.
If producers are forced by drought stress to make the first cutting earlier than the ideal time, it’s important to delay the second cutting enough to allow nutrient reserves in the roots to replenish, he added.
Where weevils are present, producers have to decide whether to spray with a pesticide first and then cut, or to forgo spraying and make the first cutting, said Jeff Whitworth, K-State Research and Extension entomologist.
“If growers decide to cut instead of spray, they need to watch the fields right after making the cutting to make sure adult weevils don’t attack the stems. If there’s little or no growth a few days after cutting, that’s an indication that the stems are under attack,” Whitworth said.
“The adult weevils chew around the bark – a condition called barking – and that restricts growth. If producers determine the weevils are still a problem, growers should go ahead and spray.”
Producers should make sure alfalfa weevils and aphids are controlled, since this will have long-lasting impacts on productivity.
If producers need to spray and swath early they can refer to the K-State Research and Extension publication, “Alfalfa Insect Management 2011” (MF-809) www.ksre.ksu.edu/library/entml2/MF809.pdf for insecticides with a very short pre-harvest interval (PHI), some with 0-1 day after treatment.