In spite of a rough start for cotton this year, cotton has made good progress and hopefully with the given warm temperature forecast, cotton will be entering into bloom pretty soon. No doubt that our crop is behind the expected, “normal” growth and development curve, but with all the moisture and warm weather we should expect to see a good crop with average to above average yield. The most talked about issue around the cotton community now is the “weed control”.
Glyphosate resistant pigweeds are reported in large number of the fields across the High Plains and producers are using both mechanical and chemical control methods to manage the weed situation on their farms.
Fortunately, on the insect side, the insect pest pressure on our cotton seems to be low and exists only in certain pockets. The area cotton is at various growth stages, but mostly at squaring stage. There are few insect pest species, which could be injurious to cotton at this stage.
Cotton fleahoppers are the primary pest during the squaring cotton. They feed on pin – head size cotton squares by inserting their needle – like mouthparts and as a result the squares dry – out and eventually drop off. Since cotton at early squaring stage has squares only on the main stem (first position), fleahopper infestation could lead to the loss of these valuable squares and significantly impact yield. However, once cotton is past blooming stage, squares on the main stem are large enough for fleahoppers to cause any injury.
So far, there are several locations in the High Plains where cotton fields have been treated for fleahoppers. Typically, when you see cotton fleahoppers in your field (25 – 30 per 100 terminals) and associated loss of pin – head size squares (less than 75% square retention on third week of squaring), it is time to make application for fleahoppers. Insecticides that can be used to control fleahoppers include but are not limited to Orthene 97 @ 8 oz/acre, Bidrin 1.6 – 3.2 oz/acre, Intruder WSP @ 0.6 oz/acre, Transform WG 0.75 oz/acre, and Carbine 50WG @ 1.7 oz/acre.
Besides cotton fleahoppers, low numbers of cotton aphids have been observed in several fields. Cotton aphids can be a pest at any growth stage of cotton provided their number is high enough. Typically, low number of aphids in our cotton is not a big concern as long as there are beneficial insects such as lady beetles, lacewings and scymnus beetles present. However, it is important to keep an eye on the aphid populations as they can grow quickly in absence of the beneficial insects, particularly in situation where a previous insecticide application knocked down the beneficial insects.
I was informed that there are few non-Bt cotton fields affected by saltmarsh caterpillars and beet armyworms, not to an extent to warrant insecticide applications. Beet armyworms can invade our cotton even before cotton starts blooming. Since they are primarily a foliage feeder, the first symptom of beet armyworm invasion is evident on the leaves. The small larvae/caterpillars feed on the underside of the leaves in groups and results in window – pane like appearance of leaves, which is called a beet armyworm “hit”.
Cotton fields with unmanaged weeds, mainly pigweed, are the most likely candidate for beet armyworm invasion. Similarly, saltmarsh caterpillars are also leaf feeders and can completely devour cotton plants. Since we had some good rain early in the growing season, there is a good chance that high number of saltmarsh caterpillars will be available in vegetation such as CRP land etc . So, be watchful for this and any other caterpillars in your cotton fields, especially if you have non – Bt acres. Please do not hesitate to reach me at Apurba.Barman@ag.tamu.edu or 806 – 407 – 2830 (cell) regard ing any cotton insect related questions. AB