Texas LRGV Cotton: Limited Thrips, Keep Watch for Aphids

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    Hot and dry this week, as winds were certainly calmer allowing for many growers to be able to get into their fields and apply herbicides where needed. I saw many growers cultivating or side-dressing fertilizer to their crops.

    Those with water were irrigating. We are forecasted for some showers over the weekend and a very hot and sunny week to follow. Driving through the counties many dryland crops are thirsty for water as corn and sorghum leaves have started to twist as the drought has stunted the growth and development of many crops.


    Cotton continues to look great down here as we have 2 – 6 true leaf cotton everywhere and cotton is squaring nicely. Thrips numbers were down this week along the river as most acreage was treated where necessary. As for the rest of the Valley thrips pressure was very little to none present in cotyledon and 2 true leaf cotton.

    Further along cotton at 5 true leaves is usually past the stage of worrying about treatment of thrips and treatment rarely justified.

    I am seeing low to moderate populations of cotton aphids in cotton. The threshold for cotton aphids is 50 aphids per leaf, however most fields I was checking I saw populations less than that (15-35 per leaf or less).

    Where I did pick up on some moderate cotton aphid populations there were plenty of ladybug adults and scymnus larva feeding on them so I would recommend coming back in 4 days or so to see if treatment is necessary or if the predators took care of the infestation.

    With cotton squaring nicely I have not seen any fleahoppers yet, and I say yet because I have seen many host plants along field margins (silver nightshade, etc.). If you do decide to treat for aphids, do not use a pyrethroid.

    Pyrethroids are broad spectrum, and kill beneficial insects as well as your target insect, but pests like aphids bounce back much quicker than their predators do. Their high reproductive rate will allow their numbers to soar after a pyrethroid application kills all their predators.

    Keep in mind if you do have to treat for aphids that fleahoppers will be coming in as well and pick an insecticide that will target both pests as cotton is squaring nicely throughout the Valley. If you happen to find ants in your cotton field, know they are not there to eat the cotton but rather they are there to eat the sugars secreted by the cotton aphids (honeydew).

    Ants and aphids share a well-documented symbiotic relationship, which means they both benefit mutually from their working relationship and it is quite fascinating to see. Ants will literally protect the cotton aphids from predators such as ladybugs and scymnus larva trying to eat them so that way they can have their sugary food source undisturbed. I’ve even read ants will take aphids to their nest at night as to protect them from predators and then escort them back to the plant the next morning.

    Grain Sorghum

    This week in grain sorghum we are seeing lots of fall armyworm activity/feeding (FAW) in the fields. Majority of fields look pretty clean with FAW feeding along the field margins, but I did come across some sorghum that had lots of feeding damage (whorl damage).

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    While FAW is a pest of concern I would really consider the stage of the FAW and whether it is necessary to treat now because most time it just looks worse than what is actually there. This does cause alarm for the future to keep in mind that FAW pressure might be higher this year once our sorghum starts to produce the grain head and we will want to protect it from FAW feeding then during soft dough stage.

    For more in-depth information on FAW check out Holly’s blog about them here.

    I am seeing an increase in corn leaf aphids in the whorls of sorghum. However, I am finding lots of ladybugs and syrphid larvae feeding on them keeping their populations in check. So that’s good plus to me that will help build up our predator populations in case we need them to feed on sugarcane aphids in the month ahead that way they are ready to go.

    As of right now seeing little to no SCA populations but after sorghum boots, we will see how it goes but right now seed treatments working well.

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