Muddy Fields and Fleahoppers

Howdy,

This week was muddy and our mosquitos are out in force, so we're still hoping for drier weather here. Our cotton is exhibiting some nitrogen deficiency symptoms since it's been so wet the past couple of weeks. Waterlogged conditions can also delay plant maturity. For more information check out this website. I have received a few questions on PGR considerations with our recent rainfall as well the best approach with our current conditions would be to apply a moderate rate once fields have dried. We want to avoid applying a high rate on fields that have experienced the stress of saturated conditions, but decisions should be made on a field by field basis. Check out this website for more information.

One of my summer field scouts started working for me this week as well. Lauren Watkins, a recent graduate from Ganado will be helping me out this summer. This week she put together an article on mosquitos, I've included it at the end of this blog update.

Cotton in Wharton County
Kate Crumley

I did not see many insect pests this week. Thrips are still out there if you have younger cotton, and cotton fleahoppers are still around. I was picking up more fleahoppers this week, and a good number of those were nymphs. Cotton fleahoppers can cause yield reduction and need to be scouted for carefully and regularly. Below are charts with my scouting information for this past week, the week of 5/28/2021.

Fleahopper feeding will cause squares to drop. Plants can recover for and compensate for some square loss, but the threshold for fleahoppers is 15-25 per 100 plants. I check for fleahoppers by inspecting the plant terminals once they start squaring. I look at 25 plants per stop in the field, usually checking 100 plants total in an 80-100 acre field, more if the field is larger. Fleahopper nymphs can be close to the size of aphids, but look like smaller versions of the adults without wings, and are much more mobile than aphids.

Cotton Fleahopper Adult
Kate Crumley

The chart below contains insecticide suggestions from cottonbugs.tamu.edu (also a good resource) for reference if you have fleahoppers at the action threshold in the upcoming weeks.

Thrips are a small (about 1/15") light tan, straw, to brown or black colored insect with a punch and suck type mouthpart and asymmetrical mandibles. They punch a hole with one side, then siphon the juice out with the other. They typically feed on one plant cell at a time, and march along punching and sucking as they go. The adults are winged, and can travel short distances on their own, or be carried by a breeze for a fair distance. Larvae hide on the underside of the leaves, often close to the leaf veins, as well as in the terminal of the plant. This week I found most hiding in the rolled up true leaf in the terminal. Feeding damage for this insect causes cotton leaves to crinkle and curl, and often looks silvery when examined. Thrips feeding can cause delays in plant maturity, which can lead to yield reduction.

Western Flower Thrips
Kate Crumley

Tobacco Thrips
Kate Crumley

Thrips are visible to the naked eye and scouting can be done by examining the plant, but it is easy to miss some of the smaller larvae. Smacking a cotton plant around on the inside of a cup will knock them off and can make them easier to count. Cotton with a neonicotinoid seed treatment is usually safe from thrips for about 2-3 weeks after planting, depending on weather and soil types. Seedlings in sandier soil will typically lose the effect of seed treatments more quickly than those in heavier clay soils. Heavy rainfall can also reduce the amount of time a treatment is effective, while not enough water can impact the plant's uptake of the treatment and also cause a reduction in efficacy.

Thrips Damage
Kate Crumley

The economic threshold for thrips is 1 thrips per true leaf until the 5th true leaf stage. Once the plant reaches this stage, treatment for thrips is rarely justified.

Cotton Aphid
Kate Crumley

The threshold for cotton aphids is 50 aphids per leaf, and if you see aphid mummies in the field (tan or black dry and unmoving aphids), that's a good thing. Parasitoid wasps lay eggs in the aphids, and the aphid forms a mummy while the wasp larvae is pupating inside. These wasps, lady beetles, and lacewings can knock back aphid populations. Treatment for aphids is rarely justified, but if you do decide to treat for aphids, do not use a pyrethroid. Pyrethroids 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 broad spectrum insecticide application kills all their predators.

Aphid Mummies on Cotton
Kate Crumley

Please check out our weekly IPM Audio Updates, the link is below. If you have any questions feel free to contact me either by email or calling the office. Have a good weekend everyone!

Check out our weekly IPM Audio Updates

How Waterlogged Soils Impact Cotton Growth and Management Decisions

PGR Management Considerations

Plant Growth Regulators as Tools for Challenges

Cotton Insect Management Guide

Development and Growth Monitoring of the Cotton Plant

Mosquito Control Feature:

By Lauren Watkins

Mosquitoes have been an ongoing problem, but with the recent rain it may seem to be worse. Mosquitoes lay their eggs in standing water, so this rain has given them ideal places for their eggs to hatch. Before you can know exactly how to control mosquitoes you need to know a little about their life cycle. Mosquitoes eggs take only one or two days to hatch, which is why they reproduce so quickly. Once hatched, mosquito larvae spend most of their time floating just under the water surface, and the larval phase can last from one to three weeks. After the larval stage, mosquitoes enter a pupal stage in order to transition from a larva to an adult. Adult mosquitoes then emerge from the pupa, seek food, and begin to lay eggs. There are many different methods that can be used to control mosquitoes such as sprays, foggers, and larvicides. These are all great methods to control mosquitoes at your home. 

Psorophora sp.
Kate Crumley

Spraying for mosquitoes will kill them with a longer lasting pesticide. A pest control professional can apply sprays to mosquito resting sites or this can be done by yourself. Aerosol or pesticide sprays can be purchased in many garden and hardware stores. Pyrethroid insecticides can last for weeks, killing adult mosquitoes on their resting surfaces. Pyrethrin, lambda-cyhalothrin, cyfluthrin, esfenvalerate, or bifenthrin are active ingredients you should look for in sprays. 

Electric or propane powered foggers provide temporary relief from mosquitoes. The chemicals used in foggers have a very short life and can be expected to provide only a few hours to a day or so of mosquito relief.  Permethrin, sumithrin, allethrin and pyrethrins are the most commonly available insecticides, and are relatively low in toxicity to people.

Mosquito Dunk in Standing Water
Kate Crumley

Larvicides are helpful when standing water cannot be drained. There are several low-toxicity products that can be used to kill mosquito larvae before they become adults. A bacterial product based on the microorganism Bacillus thuringiens is sold in the form of dunks, granules or doughnuts. These can be placed in ditches, underground catch basins or in other standing water areas where mosquitoes breed. Products containing methoprene are also good, especially for water that will remain for extended periods of time. Both of these products are safe for fish, birds, and pets.

Agrilife Mosquito Safari

Mosquito Control at Home and in the Yard

Time to Say "No" To Mosquitoes

CDC Mosquitoes

CDC Larvicides