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This is Jack Bacheler, Extension Entomologist at NCSU with the Thursday Cotton Insect Update. Today is Thursday, June 5.
Just two weeks ago, we were complaining about cool nights, and now the upcoming 7-day forecast predicts nothing under 90 degrees, with little, if any, rain in sight. We can only hope that this year is not setting up for another 2007.
At least for the time being, cotton can make do with limited moisture. That’s not to say, however, that we wouldn’t benefit greatly from 1-2 inches of rain. In the past two days, cotton fields from Johnston County out east to Bertie County for the most past looked rough and cotton in the Union County area of the Piedmont generally looked good. So, we seem to have all kinds of situations. Although immature thrips levels were only on the low to moderate side at most stops, the cool nights, wind and sand damage and feeding from adult thrips had significantly limited growth. Hard hit for the third year running was April planted cotton, particularly behind seed treatments. Even Temik-treated cotton planted in April was hurting. As of this week, most cotton had been sprayed for thrips.
With these heavy adult flights into cotton, reinfestation of thrips into cotton treated with a foliar material such as acephate (Orthene) for the most part has been occurring with about 6-7 days after the initial spray.
Although expensive, one bright spot is the apparently good thrips protection provided by treated seed plus Temik in several cotton fields. We have several such treatments on our thrips trials this year as does Ames Herbert and Jeremy Greene at Clemson, so we’ll know more about this option for next year. For the most part, several cotton fields planted around mid-May looked much better, and even most of the sorrier early-planted cotton had decent stands.
For the coming week to about 10 days before adult thrips migrations into cotton decline, be sure to focus attention to the bud area and new leaves, looking for the small immature thrips. With the aid of a hands lens, figure on about a one or more immature thrips average per true leaf as a treatment guide; thus, 4 or more immature thrips on 4 true leaf cotton would trigger a spray; less than that, probably not.
With continued hot dry weather and the further drying down of thrips hosts, the probably of western flower thrips becoming part of the general thrips species mix increases. Unfortunately, these guys are very hard to control. Three quarters of a pound active, or 12 ounces of Orthene or acephate, is about as good as one can do for ‘westerns’. However, Ames Herbert of VA Tech mentioned via phone last week that even this rate came up short with a couple of producers up his way. As far as we know, there are no miracle materials out there, and products like pyrethroids, Cygon, Bidrin, Vydate, dimethoate and others are not going to save the day when it comes to westerns.
As a general rule, 5 true leaf cotton can withstand feeding from westerns and our more common tobacco thrips, and treatment is normally not required. Also, if the newest leaves in the bud area are expanding straight and shiny, that often signals minimal thrips feeding. Much of our cotton should fall within this category in the coming week. Significant rainfall would also be a big big blessing.
To date, we have not received reports of spider mites or cotton aphids. Our present weather conditions and high levels of seed treatments would seem to be ideal for spider mite infestations, though after a very dry start in 2007, mites never materialized in a big way.
We just learned today that the boll weevil eradication producer fee for the 2008 trapping and containment program was set at $1.25/acre, lower than the earlier projection of 2.10 and half of the 2008 assessment.