During this time of year, pest control advisors (PCA’s) and growers are dealing with a variety of insect pests in the two major field crops in central Arizona, alfalfa and cotton. In alfalfa, leafhoppers are major pests during this time of year. While scouting several fields this week, I noticed that hoppers [Potato Leafhopper and Three-cornered Alfalfa Hopper] were not as abundant as last year, but they approached levels that warrant management decisions in certain fields. The following two links from UC [http://www.ipm.ucdavis.edu/PMG/r1301211.html & http://www.ipm.ucdavis.edu/PMG/r1301611.html] provide information on description, damage, monitoring and management of these leafhoppers.
Leafhoppers are not the only insect pests we can find in alfalfa during the summer. Caterpillars are another group of insect pests that can be harmful to alfalfa during the summer. Mainly, we have three species of Lepidopteran larvae in alfalfa, Beet Armyworm: Spodoptera exigua, Western Yellowstriped Armyworm: Spodoptera praefica and Alfalfa Caterpillar: Colias eurytheme. Cutting the hay can mitigate caterpillar damage. Proper identification of these species is important because they have different economic thresholds. Using the economic threshold is crucial when the crop is too early to harvest and you decide to apply a treatment.
The following links from UA http://cals.arizona.edu/pubs/insects/az1045.pdf and UC http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=10907, http://www.ipm.ucdavis.edu/PMG/r1300711.html, http://www.ipm.ucdavis.edu/PMG/r1300811.html, http://www.ipm.ucdavis.edu/PMG/r1300611.html provide information on description, damage, monitoring and management of these caterpillars.
In cotton, primary pests like whiteflies and Lygus bugs, are scouted closely by PCA’s and growers at this time of season. Both pests can be managed by different approaches, such as biological and cultural control. When chemical measures are justified through sampling and the use of economic thresholds, selective insecticides are the best choice to help our cotton IPM program in Arizona. Selective insecticides are safer to the user, environment, and natural enemies that maintain secondary pests below economic levels and help control our primary pests. The University of Arizona Pest Management Center published several short 1-page bulletins on cotton pest management decision making to help PCAs and growers in their decision making. Here are some of these related publications:
1) How to determine when to make the last effective Lygus spray, if Lygus are over threshold http://ag.arizona.edu/crops/cotton/files/LygusTerminationShortvF.pdf
2) How to sample for whitefly threshold in 7 minutes or less http://cals.arizona.edu/apmc/docs/WhiteflySamplingShort.pdf
3) Key selective chemistry that helps our insect cotton IPM program http://ag.arizona.edu/crops/cotton/files/KeyChemistryShortvF.pdf