The following update was prepared by Clemson Peanut Specialist Dan Anco.
Recently, rains have been bringing much needed water to several areas. By now many peanuts are around the 75 DAP mark, and rows are becoming increasingly closed. Having enough soil moisture available during this time helps with pod filling, and this is when peanuts generally use the most water. In addition to getting our fungicide applications down for disease protection, we can be keeping an eye out for disease development and caterpillars feeding on foliage.
Fungicides: When putting together a fungicide program, we have a number of products to choose from. Research coming out of Florida has been showing that if we will be using several premium fungicide sprays, we get a more consistent increase in disease control if we include three modes of action over the season, with this effect relying less on which particular products are used (within reason). If we are using a program that has two modes of action, disease control can still be considerably good, but there is often a greater range of control that depends more on our choice of products. Not only is increasing the number of different fungicide modes of action good for improving disease control, but it also goes a long way in preventing development of fungicide resistance. Preventing fungicide resistance development is important to keep on the radar, since it helps ensure that the products that are effective today will continue to be useful in years to come. This year’s budget may be a bit tighter for many of us, but if you are planning on putting out several premium products, increasing different modes of action is something to consider. The mode of action for each product can be found on its label as well as in the production guide. Here is a poster with some recent disease control data:
Insects: When looking at insect damage, getting a positive identification on the pest greatly improves our ability to manage it, though some can be challenging to separate (for example, corn earworm vs. tobacco budworm caterpillars). Pyrethroids are certainly less costly than many insecticide options, but they do not work for everything, and they are not recommended for tobacco budworm, armyworms, or granulate cutworms. See the production guide (pg. 57) for a list of recommended products.
While corn earworm and tobacco budworm caterpillars can appear identical without magnification, if we are able to see enough adults to get an idea of which one we are primarily dealing with, we can make a more informed management choice. Here are some pictures from Jeremy Greene that can help tell the two species apart:
While the adults may help us determine which pest we’re dealing with, it is the caterpillar numbers that are more useful in guiding the decision of whether to put out an application or not.
For those who haven’t seen it before, here is the scouting recommendation and treatment threshold from the production guide:
Scouting for Foliage Caterpillars: Use a 3′ shake cloth to look for worms starting the last week of July. Work the dowel handle up under lateral stems to the plant crown and bend the other side of the plants over the cloth. Beat down vigorously 15 times to knock worms onto the cloth. Shake the plants, bend them back out of the way and count the worms on the cloth. Also count worms under the cloth on both sides of the row to calculate worms/row ft. Check at least three areas/field.
Rank-growing, unstressed peanuts with a closed canopy can tolerate 8 foliage feeding worms per row ft. The treatment threshold is 4 worms per row ft on stressed plants which have not lapped the middle or where Lorsban has previously been applied. Runner varieties with slow growing canopies can be more susceptible to direct injury from foliage feeding. Weed control may also be affected by delayed canopy closure on runner varieties. Irrigation, vigorous canopy growth, and avoidance of unnecessary early season insecticide applications are the best defense against foliage-feeding worms.