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    Texas LRGV Pest Management: Sharp Increase in Plant Bugs in Cotton

    Tarnished plant bug up close. Photo: Mississippi State University

    General Situation

    Very hot and dry again this week in the Lower Rio Grande Valley. Lots of work going on in row crops as Valley growers are doing everything from cultivating sesame, harvesting grain sorghum, corn and sunflowers to irrigating cotton, and applying PGRs/insecticide treatments in cotton as well. Heat units are accumulating fast as we get closer to reaching harvest time in cotton.

    Cotton

    This week is the week of the plantbugs! We have been sweep netting many cotton fields for Verde and tarnished plant bugs and have seen from last week a sharp increase in populations as many have migrated out of sorghum into nearby cotton fields. Many cotton fields have been treated this week for plantbugs. The infestations of plantbugs have been seen in all cotton Valley wide.

    I highly encourage those with cotton still in full bloom stage with younger dime size bolls to go and inspect for plantbugs and treat accordingly. Verde plantbugs and tarnished plantbugs like to penetrate and suck juices from the smaller bolls hence ruining fiber quality. Still seeing some moderate whitefly pressure in mid Valley around Edinburg, Elsa, and Monte Alto and then some high whitefly populations along the river in the Pharr, Donna, and Progresso areas.

    Whiteflies feed on cotton excreting sugars that cause black sooty mold to develop and inhibits cotton plant growth and once we have open bolls sometimes the sooty mold can stain the open boll cotton if we receive rains. We are also picking up on a rapid increase in chilli thrips in cotton field margins along the river. Chilli thrips can cause severe bronzing and defoliation of the leaves when populations are left unmanaged and can reproduce rapidly as they thrive in this intense heat.

    Grain

    Majority of sorghum in the Valley is mature and drying up for harvest or being harvesting right now. I am hearing yields of 4500-6500lbs per acre being harvested in grain sorghum just depends what area you are in. We have a little bit of sugarcane aphid populations we are seeing but they are being controlled by many predators and nothing to be concerned about right now.

    More on Cotton


    I saw some sorghum that will be heading out next week, if you have sorghum barely going to be heading out and flowering just know that there are heavy midge populations out there in some flowering sorghum we’ve been able to find on field margins and so late planted sorghum will need to be treated for midge as soon as it starts to flower and will need to be inspected for midge populations at least every 3 days until its done flowering in order to protect seed development.

    I have also been checking some sorghum in early vegetative stages (V1-V5) and finding heavy fall armyworm pressure, about 1-2 per seedling so please check late sorghum and if you are seeing high armyworm pressure like that know that treatment should be considered.

    Sesame

    Not too much going on in sesame this week. We are starting to pick up on a couple of mirid plantbugs but nothing that warrants treatment. I am also seeing many tarnished plantbugs lingering in the leaves of the blooming sesame, they do not seem to be causing any damage to the pods and I have not seen them cause damage in years past when they have been present in the sesame, so we are just going to continue to monitor them.

    Most importantly is I am not seeing any sesame leafroller pressure… so far so good. A lot of the earlier planted/mature sesame is starting to dry up for harvest next month.

    Soybeans

    I was able to do a little bit of sweep netting in soybeans this week and was picking up on quite a few green stinkbugs. Scouting soybeans is still new to me as I am learning more about the crop but my colleague Stephen Biles – IPM agent in Victoria, TX recommends to scout soybeans until the beans reach maturity as they are susceptible to stink bug damage. Some entomologists would say soybeans are safe when the beans reach R7 (one brown bean per plant).

    Others suggest the beans are still susceptible to economic damage until more of the beans on the plant are mature. For most stink bugs in soybeans use an economic threshold of 36 stink bugs per 100 sweeps or 1 per ft of row. Red banded stink bugs have the ability to cause greater amounts of damage so use a lower threshold of 18 red banded stink bugs per 100 sweeps or 1 per 2 foot of row.

    I am seeing a mixture of southern green, red banded, and brown stink bugs in soybeans right now and noticed nymphs mixed in with the adults so we will probably be at threshold in some soybean fields next week. Those growing soybeans will want to inspect for stinkbugs from now till harvest.




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