Temperatures in the lower Rio Grand Valley were in the low to mid 90s but felt much hotter with the heat index. Many growers were seen cultivating, irrigating, and applying spray treatments to their crops this week as the season progresses. Received a little bit of rain this morning across the valley, enough to cool off.
Our oldest cotton is just about to bloom while most other cotton is in peak squaring mode. About the same pests as the previous two weeks were found in cotton this week. While scouting you could tell if a field had not been treated because it had plenty of cotton fleahopper (adults and nymphs) and cotton aphids present. Many growers are spraying for both. Some growers were already having to apply second control application this week for pest management.
I did see very light red spider mite populations in Raymondville and in the Weslaco areas which hopefully were knocked off with this morning’s rain. Still seeing good predator populations in the majority of cotton throughout the valley. Scymnus larvae feeding on cotton aphids as well as more aphid mummies due to parasitism.
We need to diligently in monitor for fleahoppers and keep them under control if we want to produce good yield at the end of the growing season. Fleahopper adults and nymphs like to feed on the squares by sucking the juices causing cotton squares to just dry up, turn brown/grey and fall off. During the first 3 weeks of squaring 15-25 cotton fleahoppers (nymphs and adults) per 100 terminals may cause economic damage. When scouting for fleahoppers, each time you sample (weekly is good) you will want to check 25 terminals in at least 4 locations of a field starting when the first squares are appearing. If you notice anywhere from 15 to 25 fleahoppers per 100 terminals with squares being lost (rule of thumb: 10% the first week of squaring, 15% the second week of squaring, and 25% the third week of squaring, with treatment rarely needed after first bloom) treatment is justified.
In parts of Texas we have found evidence of bollworm resistant to one or more Bt genes in our Bt cotton. Fortunately for South Texas we have not seen or experienced increased bollworm pressure. However, if you do have a Bt cotton field that has bollworm pressure this year please contact me, (Danielle Sekula, 956-968-5581) so we can inspect and collect the larvae, if need be. We would like to be ahead of any resistance issues and are asking for your cooperation in protecting our cotton crop.
Some of the earlier planted sorghum is already in the soft dough stage. We saw much more sorghum flowering this week as we inspected for sorghum midge, which we didn’t find. I did picked up a couple rice stink bugs just starting to enter sorghum fields out east of Raymondville. Yellow sugarcane aphids have been very present on the lower leaves of the canopy throughout the Valley. We will need to keep an eye on them since a couple of years ago out in Willacy they started to colonize on the upper 3 leaves seeming to cause detriment to the plant. Some growers had to spray.
Earlier in the week I did put out an alert about sugarcane aphids in sorghum because we were noticing more colonies forming in all counties and migrating as well. I saw a few fields with populations along Military highway/river that needed to be treated. Other areas in the mid valley and out in Willacy county had a few colonies of sugarcane aphids along a fields edge (lets say 100 acre block). But, once you get in there and walk further they are not present throughout and the fields are pretty clean.
When I do find these pockets or hotspots of sugarcane aphids I look to see what predators are present. I have been pleased to see parasitism present along with and lacewing larva munching away on these sugarcane aphids keeping them from spreading into the rest of the field. Granted it there have been some fields that needed treatment but still not seeing half the pressure we have seen in years past when they first came onto the scene.
*Scout your fields by simply walking in at least 4 areas throughout, pick at least 10 leaves in each location and examine for sugarcane aphids, 40 leaves total. If it averages out to 50 aphids or more per leaf, then treatment is warranted. However, make sure to consider predator populations and accumulation of honeydew. I say this because we are seeing hotspots in many fields but it’s not quite time to pull the trigger because the colonies have not spread throughout the field and are being controlled by predators and parasitism.
Dryland corn was looking very stressed this week during its time of reproduction due to lack of water. Sesame continues to develop as the majority is past germination and into the seedling stage, juvenile (first buds) or pre-productive stage. I did find some sesame blooming and there were a handful of aphids present but otherwise looking good.