This has been a busy field season so far. We have had just about every kind of pest pressure, and it doesn't seem to be letting up yet. Fortunately, Jackson and Matagorda county cotton is nearing cut-out, and the corn and sorghum is wrapping up in Wharton county. We are planning on harvesting the Wharton county sorghum trial on Tuesday. As folks are harvesting grain, many of the insects that were feeding in those fields will be moving into cotton in force. We'll be needing to keep a close eye on bollworm, armyworm, verde plant bug, and stinkbug numbers. It has dried out a little now, and aside from the spotty showers we've had, some fields are starting to dry out. Most of the grain crops are past watering, and are drying down and nearing harvest. I know many of the fields I have seen are rain fed only, but if you do have the ability and inclination to irrigate, keep in mind that once cotton reaches about 5 nodes above white flower (NAWF) it is unlikely that irrigating will have any impact on yield.
Currently we are watching the bollworm populations pretty closely. We even have pretty heavy pressure in all of the Bt varieties. The egg lay has been pretty high, and is going to increase as the corn and sorghum finish. Eggs are usually on the top of the plant, but they can lay eggs anywhere on the plant. I have been finding eggs laid either on blooms or on bracts, both of which have lower expression of the Bt trait. There is a greater chance of survival when the caterpillar feeds on the flowers and bracts before trying to move into the bolls. The action threshold for these escaping caterpillars is 5,000 worms/ acre with more than 5% damaged bolls when checking three plants at a minimum of four locations in the field. I have been seeing damage that high, and many of you have made treatments. This website has a decent chart on what insecticides work on bollworm if you do have to spray them. The chart leaves out a few trade names, but is comprehensive with the chemical names. If you are seeing incredibly high bollworm populations (i.e. over 25-30% of plants infested), please don't hesitate to contact me.
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| 3-4 day old H. zea larvae (Bollworm) Photo: Kate Harrell |
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| 5-6 day old H. zea larvae with cotton aphid Photo: Kate Harrell |
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| Armyworm egg mass Photo: Kate Harrell |
We need to continue to keep an eye on sugarcane aphid populations this close to harvest. The threshold is 50-125 aphids per leaf, treat within 4 days of reaching threshold. If we allow them to get out of hand at the end, the honeydew produced by these aphids along with the sooty mildew that tends to grow on it can really gunk up a combine. With the majority of our sorghum being a little earlier, hopefully we will miss the worst of their populations.
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| Unconventional Beneficial Photo: Kate Harrell |
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| Unconventional Beneficial Photo: Kate Harrell |
I'd like to say thank you to everybody that invited me to field days this past month, and to the folks who have shared all kinds of summer produce. It was all delicious. Have a fantastic 4th of July, and stay safe, everyone!
Kate
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