Army worms march on
Tuesday, May 28, 2013 11:52 am
Scott Stewart, IPM Extension Specialist
I've had several questions this week about whether an insecticide should be included when spraying a fungicide when spraying wheat. My general response to questions like this is "no". It is the same question I frequently get in soybean and the same answer. It is like asking me if you should spray for plant bugs at first bloom. If there are pest present at threatening (threshold) level, then we should definitely take advantage of piggy-back applications. I often recommend preventative insecticides in high risk/reward scenarios. The use of seed treatments in cotton is a good example. Another example is my recommendation to spray low populations of aphid in wheat during late winter for the prevention of barely yellow dwarf virus. However, throwing an insecticide in the tank "just because" is not responsible. It adds unnecessary cost and does not promote the reputation of farmers as being good stewards of the environment.
Enough of the soapbox! There are a couple of pests to keep an eye out, namely true armyworms and cereal leaf beetles. I've heard only rumors of infestations this year, but you should scout for these pests regularly and especially before making a fungicide application. Treatment thresholds and insecticide options are available on UTcrops.com at Insect Control Recommendations for Wheat.
True Armyworm. This caterpillar may cause yield loss if excessive defoliation occurs during or before the milk stage. UT recommends treating for armyworms when 6-8 larvae are present per square foot and wheat is in the milk stage (or less mature). Pyrethroid insecticides are most common used and are effective. Labeled pyrethroids include Baythroid XL, Declare, Karate/Warrior, Mustang Max (among others).
Cereal leaf beetle larva
Cereal Leaf Beetle. The adults and larvae of this insect may occasionally cause premature defoliation, but it is larvae that really cause almost all of the defoliation. The beetle larvae cover themselves with their own gooey feces. It is usually pretty obvious when you have many because they stain your pants when you walk through the field. Treatment is recommended when 25 or more larvae are present per 100 tillers. The pyrethroids listed above are also effective at controlling this pest.
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