MID-SEASON PEANUT UPDATE
VELVETBEAN CATERPILLARS AND DIMILIN
The mixture of low-level worms of different species that have been ragging up our peanuts have for the most part cycled out and velvetbean caterpillars (VBC) are the primary species. I am starting to see moths and low levels of VBCs in our peanut fields. VBCs are voracious feeders and can quickly defoliate a peanut or soybean field. I believe a Dimilin 2L application of two ounces per acre in a grower’s next fungicide spray would be a wise option and generally eliminates the need for additional insecticides for worms. We have seen VBCs be a severe pest in mid-to-late August in Coffee County and this may save growers from having to make a solo spray.
Dimilin has excellent residual and normally gives season-long control of VBCs. Dimilin will also help control or suppress other caterpillars including green cloverworms, armyworms (beet, fall and yellow-stripped) soybean looper (suppression) and grasshoppers. Dimilin is not an insecticide but an insect growth regulator that interferes with chitin deposition (chitin is the protein that serves as the cell wall) and the worms are unable to form an exoskeleton. Worms are unable to successfully molt after eating it and go to the next stage. Dimilin is not systemic so good coverage is critical. Dimilin may not work as well with night fungicide sprays when the leaves are folded and will not protect new growth put on after it has been sprayed.
Young velvetbean caterpillars “loop” when they crawl until they are about ½ inch long. They can be distinguished from loopers since they have four pair of prolegs (hind legs) and loopers only have two. They also have a yellow head capsule and will wiggle violently when they are disturbed or handled. They are usually green with yellowish-white stripes running down their bodies. Brown or black color phases with yellow stripes may also be found late in the season when populations are high.
VELVETBEAN CATERPILLAR MOTH
THREE-CORNERED ALFALFA HOPPERS
I have been seeing plenty of three-cornered alfalfa hoppers in peanut fields but very little damage. Last week I saw the first field with enough three-cornered alfalfa hopper damage that an insecticide spray would have been justified earlier in the season. Dr. John Beasley, University of Georgia Extension agronomist, has noted high three-cornered alfalfa hopper populations throughout Georgia but very little damage. You can listen to his comments on three-cornered alfalfa hoppers at OTF-Beasley3CAH7-29-12 . Three-cornered alfalfa hoppers do not seem to prefer feeding on our new varieties of peanuts (Georgia 06G, Georgia 07W, etc.) like they fed on Georgia Green. Besides high yields and excellent disease resistance, it is another advantage of these new peanut varieties.
Three-cornered alfalfa hopperS feeding on stems will cause a thickened callous tissue or girdle that encircles the stem. The stem will often turn purple above the callous area and the terminal will eventually yellow.
THREE-CORNERED ALFALFA HOPPER
THREE-CORNERED ALFALFA HOPPER DAMAGE
IRRIGATION AND DISEASE CONTROL CRITICAL
The Coffee County peanut crop is in excellent shape but mid-season irrigation or rainfall (2 inches per week) are critical now. Listen to Dr. Beasley comments on the importance of mid-season irrigation at OTF-BeasleyMidSeasonIrrigation7-29-12 . Also I talked with Dr. Tim Brenneman, University of Georgia pathologist, and he says there has been a major outbreak of white mold last week so stay on a good fungicide spray program.