The Alabama Peanut IPM program conducts routine pest monitoring using sticky wing traps from various locations statewide. Based on trap catches from May to August 2017 (see illustration on the left), it is evident that the above-normal rains in June and July disrupted moth activity for many species; this resulted in a 'quiet' time when we didn't see very many caterpillars on peanut foliage. The only insect that appeared to maintain a high activity in crops during the rains is the beet armyworm, which appeared very early on the foliage also. Cool temperature and wet weather is also good for beneficial insects that are able to catchup with low caterpillar populations. Overall, moth activity is rapidly increasing for loopers and armyworms. Our peanut research plots in Headland are now riddled with holes with caterpillar numbers between 2 to 3 caterpillars per foot of row. In other words, peanut producers should be on high alert for defoliation and intervene before the threshold is reached. Some of the new peanut varieties with vigorous growth seem to tolerate a high caterpillar number but don't risk a late season outbreak of foliage feeders. Also, wet weather causes three-cornered alfalfa hoppers and leaf hoppers to increase rapidly – we do not want them to go deep into the canopy and feed on pegging branches.
Caterpillar control in commercial fields should include a variety of materials. See illustration on the right to understand some of the selective insecticides available for peanut producers. Note the 'spider mite risk zone' on the illustration – that is when caterpillar feeding is at peak on the peanut and we get the most complains of spider mite flare up due to excessive use of synthetic pyrethroids. Therefore, synthetic pyrethroids are mentioned outside the 'spider mite risk zone' as a way to slow down or stop caterpillars with minimum applications. Chemicals belonging to Class 5 (spinetoram), 15 (diflubenzuron, novaluron), and 18 (methoxyfenozide) have long residual and are selective materials for small caterpillars. Those insecticides are great for drought year when plants may be stressed and we need to protect natural enemies. Premix insecticides such as Beseige can be helpful to manage caterpillars and leaf hoppers, such as in rainy years. Xentari (a microbial insecticide) does very well for caterpillar control in early season; repeated applications are necessary to manage armyworms and other species.
To know more about the various caterpillar species in peanuts (insect identification), please see this blog article. For more details, please call an agronomic crops regional extension agent or go online for downloading the 2017 Peanut IPM Guide. The Alabama Peanut IPM program also has a mobile-friendly website and sends additional pest alerts via Facebook.
Ayanava Majumdar, Extension Entomologist
Kris Balkcom, Extension Agronomist
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