How to identify thrips in cotton

 

Jeremy Greene: Thrips are a group of insects that attack cotton and they are a perennial pest, our producers have to deal with this group of insects every year. Thrips can cause significant injury if a preventive material is not used. Those include: seed treatments, in-furrow granular materials, in-furrow liquid materials and all those materials provide systemic protection from thrips under optimal growing conditions. The right amount of moisture, the right amount of heat and if those are off, the systemic nature of the insecticide is not optimally taken into the plant and does not provide control of thrips. What we have had this year, we have had a lot of rain that has made those systemic materials leach out of the ground and not be optimally taken into the plants. We have had a lot of thrips injury this year.

Temik is very effective but it is in short supply and it is not being manufactured, so that is probably not going to be a viable option in the future. Thimet is a granular material that continues to be manufactured, it is readily available. It provides control of thrips in-furrow, but it does not provide control of nematodes, that is the kind of control we got from Temik, both thrips and nematodes. The in-furrow liquid products that we have, one of the predominante ones that we are investigating is Imidacloprid. It looks very good in-furrow, we are looking at a nine-ounce rate of Imidacloprid and it looks really good for thrips. Again, no control of nematodes, so there is kind of a dual issue here with control of nematodes and thrips with a lot of these at-plant options and that was pretty much started with Temik, Aldicarb.

As that is a fourty-year old product and folks had gotten used to managing both thrips and nematodes at planting. Now, it is a little more difficult with the removal of that product from our system. Well, as you can see here, we are next to a pair of plots where we have untreated plants and that received nothing at-plant for preventive protection from thrips. And right next to that, the row adjacent to that is a seed treatment. This particular seed treatment has chemical Thiamethoxam and is a common seed treatment used in the industry and just a seed treatment, no foliar protection versus untreated. You can see the extensive injury on this cotton planted on the fifteenth of May, extensive injury from thrips and what a seed treatment did here in sunny South Carolina in two thousand thirteen. So here we are by another pair of plots where we have untreated plants right here beside me and over to my right we have another preventive at-plant treatment for thrips. This one happens to be Imidacloprid in-furrow at nine ounces. Also a very good at-plant option for thrips versus doing nothing.

Alright, here we are next to another pair of plots. I am sitting next to an untreated row and right next to me is a plot protected with one of our growers’ favorite chemicals of all time: Aldicarb, Temik, showing very good protection against thrips in contrast to doing nothing for thrips in an untreated situation. Here we are again in another pair of plots, demonstrating untreated protection from thrips and another granular material that is labeled for use on thrips: Thimet. This is Thimet versus untreated and it does not look as good as the Temik but it is a very option for our producers for thrips. When making a treatment decision with foliar insecticides for thrips after an at-plant treatment is applied, the plants are actively growing and you are starting to show signs of injury from thrips, I use one of two methods. I use a nice big white cup to shake the plants inside and dislodge the thrips for counting. Or some sort of dark cloth that enables you to see the immatures easily on the cloth.

Using a couple of these different methods when you are walking through a field and sampling numerous plants will give you a pretty good idea of the density of thrips on your cotton crop. In addition to using these two sampling methods, I like to visually inspect the terminal growth of cotton. If you are looking at the new growth, the new leaves coming out of the meristem stem, you can easily see the thrips injury, the crinkling of the leaves, the silvering sheen that is left by the feeding. And if you start to see an excessive amount of feeding there, that is also an indication that your at-plant treatment has played out and it is time to intervene with a chemical foliar insecticide. To summarize, thrips are an important group of insects that attack cotton, they cost our producers millions of dollars each year in control costs so you want to be timely with foliar insecticides applied after at-plant materials are played out on those plants, so please consult our most updated recommendations for controlling thrips.