They’re Back! Be On the Lookout for Early Aphids in Alfalfa and Share Your Observations!

Alfalfa & Forage News

sitenum=237

News and information from UC Cooperative Extension about alfalfa and forage production.

Author: Peter B Goodell

Published on: January 16, 2014

Early reports are coming in from PCAs that Blue Alfalfa Aphid (BAA), as well as other common aphids, are already making their appearance in alfalfa.

Photo by F Moitoza, 2014. Click to enlarge

In 2013, there were widespread but localized outbreaks throughout southern and central California including locations in the Imperial, Palo Verde, Antelope, and San Joaquin Valleys. Within the San Joaquin Valley, western Kern and southwestern Merced County were most severely affected.

This earlier than normal aphid appearance has come as a surprise as many alfalfa fields are not normally being scouted during January. The attached photos indicate the severity of the build-up on seedling alfalfa. Reports from Merced and Kern Counties indicate early and high populations.

We do not understand all the reasons for this outbreak but a key factor may well be our dry and warm conditions. The 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 (See previous Blog posts by Barlow; http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=9640). While some December days were cooler in 2013 than 2012, January 2014 has been warmer than 2013 and the 30 year average.

Deviation of daily mean temperature from 30 year average. Click to enlarge

UCCE farm advisor Carol Frate remembers that several years ago, when another unusually warm January occurred, a number of established alfalfa fields in Tulare County experienced damaging levels of cowpea aphid. This aphid thrives under warm and even hot conditions, making the January damage very surprising. While watching for BAA, also keep an eye out for the cowpea aphid. For aphid identification tips, see Godfrey’s previous Blog post (http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=9639)

In an effort for to stay on top of the aphid outbreak in 2014, readers are encourage to report their observations via this survey link (https://ucanr.edu/survey/survey.cfm?surveynumber=12133). The survey is 4 questions and should only take a few minutes to complete.

Management of aphids in alfalfa will likely be challenging in 2014 based on their early appearance and last year’s problems. Insecticide options are limited, especially prior to alfalfa weevil season. Cultural controls (primarily early cutting for 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.

Communication and networking within the alfalfa community will be extremely important in any success we can have. Follow this blog closely and watch for information as it becomes available.

Photo by F Moitoza, 2014. Click to enlarge

Comments: 5

Comments:

by Vern Marble

on January 17, 2014 at 10:46 PM

Interesting article> I found the black aphid on a few seedling stems about a month ago. the location was in Solano Co. near Rio Vista. Last Wednesday I cold not find any aphids.

by Gregory E. Sprawls

on January 25, 2014 at 10:18 AM

I manage 5,000+ acres of alfalfa between Blythe California and Parker Arizona along the Colorado River for the Colorado River Indian Tribes. The cow pea aphids have been building and the blue aphid arrived early. There are 3 different bug men trying to suppress the populations with little or no success. We need more tools in our tool box to deal with this pest!! We seem to just be raising the rates, but that too has bad consequences.

by Tim Hays

on January 28, 2014 at 7:47 AM

I am seeing large numbers of Cowpea and low numbers of Blue aphids. The alfalfa is just starting to green up in this area, if it has been watered. Different then last year , there are many ladybird beetles. The Ladybirds present represent several species. We are not spraying and hoping they can bring aphid numbers down. We had poor control last year and want to avoid a repeat of that.If needed later, we will treat.

by Tim hays

on February 10, 2014 at 12:59 PM

Aphids very heavy many fields . Some fields being sheeped off to reduce aphids. Finding weevils now on very short hay . Treatment will be needed soon.
Trying to avoid pyrethroids to save beneficials. Still trying to find cure for blue aphid. This is the window of time where a good selective aphidcide would be so usefull.cowpea numbers decreasing blue increasing.

by Tim hays

on February 10, 2014 at 1:01 PM

Aphids very heavy many fields. Some fields being sheeped off to reduce aphids. Finding weevils now on very short hay. Treatment will be needed soon.
Trying to avoid pyrethroids to save beneficials. Still trying to find cure for blue aphid. This is the window of time where a good selective aphicide would be so useful. Cowpea numbers decreasing, blue increasing.