Aphids infested seedling alfalfa in parts of California in January, a month growers and farm advisors don’t usually scout for the pests. Reports from Merced and Kern counties indicate early and high populations.
As if a severe, three-year drought weren’t enough for California alfalfa growers to deal with, now aphids are making earlier-than-usual appearances.
In 2013, widespread-but-localized aphid outbreaks were cited throughout southern and central California, especially in San Joaquin Valley’s Kern and Merced counties. Those two counties are also reporting high populations of Blue Alfalfa Aphids (BAA) and other common aphids already this year.
Dry and warm conditions may be the key factor, says Peter Goodell, integrated pest management specialist with University of California (UC) Extension. In a recent post on UC’s Alfalfa & Forage News blog, he notes that lack of moisture has limited fungal infestation and reduced stress on aphid populations.
“Lack of fog may also be influencing population development. The cool nights and warm days provide average daily temperatures which are reportedly conducive for BAA. While some December days were cooler in 2013 than in 2012, January 2014 has been warmer than (January) 2013 and the 30-year average.”
Pest management may be challenging, he adds. “Insecticide options are limited, especially prior to alfalfa weevil season. Cultural controls (primarily early cutting to control some aphids) are not acceptable at this stage of the season. Biological control was weaker last year, and early appearance of aphid will challenge natural enemies to catch up.”
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