Cotton Insects This year, on average, we reached 5 nodes above white flower (NAWF) near August 8. Which by my standard is just a day or so later than normal for our area. Based on my data as the Levelland National Weather Service Observer for August 8-22 we have accumulated 315 heat units. So, by this next week (August 29-31) most of the cotton acres in our program area from Ropesville to Morton and north near Littlefield will have sufficient heat units to meet the criteria of 5 NAWF + 450 DD60 Heat Units to be safe from economic insect damage. The exception to this is cotton aphids. I will continue to watch cotton aphid for some time. So, this is not the “all clear, everyone walk away from the cotton” signal. However, the signal to be very careful in spending money to control an insect situation that will not return in final yield has been given.
Cotton Nematodes Now is an excellent time to soil sample for cotton root-knot nematodes. Soil sampling is important in determining populations of plant parasitic nematodes capable of reducing yield. Nematode samples collected prior to harvest may give the best estimation of nematode populations. In collecting soil samples, several factors, such as sampling method(s), sample preparation and handling and field conditions must be taken into consideration.
Several methods can be used in obtaining soil samples. Samples should be collected samples (from 1/3 of the field each) should be collected per field. Additional samples may be required if dealing with different soil types in a field. A composite sample consists of 15 to 20 soil cores taken from a depth of 12-inches using a soil probe, or a narrow-bladed shovel. Samples should be taken within a 4-inch radius of the taproot, as it is important to have root fragments present in the sample. The soil cores should be placed in a bucket and thoroughly mixed, being sure that any dirt clods are broken up. A sub-sample of 1-quart should be placed in a sealed plastic storage bag. Nematode samples need to be kept cool (not frozen), and out of direct sunlight. In addition to the collection and handling of samples, field conditions at the time of sampling may impact test results. Close attention should be paid to the amount of soil moisture at sampling. Samples should not be taken if the soil is too wet or too dry. Samples should be sent to a qualified laboratory capable of making microscopic evaluations to determine populations.
Grain Sorghum Sorghum aphids (once known as sugarcane aphids), yellow sugarcane aphids, cornleaf aphids, stinkbugs, and headworms can all be found in area fields. The cornleaf aphids have been good fodder for beneficials to establish on. Between these beneficials and the heat sorghum aphids and headworms have had a hard time of it. However, each field is different and must be scouted to determine if these pests warrant treatment based on thresholds.
Peanuts are at the end of their bloom period like cotton. Pods will continue to be formed on pegs for the next few weeks and so that environment in canopy needs to be conducive for that process. Along with that environment comes increased incidence of foliar disease this time of year. Conditions from irrigation, morning dews, cloudiness, rain events, moderation of temperatures etc. create these conditions where disease can be common. All that said, I would encourage an end of season fungicide application to protect vine health.
Elm Leaf Beetles Well, lot of folks have been asking about the elm leaf beetle damage which has occurred on most all elm trees (with some exception to the lacebark and cedar elms) here in Levelland and all the South Plains of Texas. These beetles have been present for many years and have caused much damage in the past. However, I have never noted it to be as bad as it is this year. Most years a good cold winter will knock their overwintering numbers back considerably. The damage we are seeing at present would tell me last winter had little or no effect.
Adults are about 1/4 inch long and light yellow to brownish green. Several black spots decorate the head and thorax, and a broad black stripe follows the outer margin of each wing cover. Overwintering adults are darker and duller than summer adults. Eggs are laid in clusters of five to 25 on the undersides of leaves; they are yellow-orange and pointed on the outer end, resembling miniature lemons. The newly hatched larvae are black. Mature larvae (photo above) are pale yellow with two black, interrupted stripes down the back; they are about 1/2 inch long. Pupae are 1/4 inch long and bright orange yellow with scattered black bristles.
Elm leaf beetles overwinter as adults in any sheltered, dry place that gives them protection. Overwintering adults sometimes enter homes, where they become a nuisance on warm days. The insects do not infest food or other household materials but simply spend the winter indoors. In spring, beetles fly to elm trees shortly after foliage emerges. They eat holes in new leaves and soon deposit eggs. A single female may produce as many as 400 to 800 eggs. Slug-like black larvae hatch in about a week. The larvae feed for about 3 weeks on the undersides of leaves; when they mature, they crawl down the tree to gather in large masses at the base of the trunk (or any other nearby, sheltered place) to pupate. Adult beetles emerge from pupae about 2 weeks later. Three or more generations occur each year in Texas. In late summer and early fall, the adults begin to seek overwintering sites. Elm leaf beetles feed exclusively on foliage. Adult feeding causes small, circular holes in leaves. Larval feeding removes most of the green material from leaves, leaving them dry and brown with only the leaf veins remaining. Heavily infested trees have sparse foliage; remaining leaves are riddled with holes, have a rusty, reddish-brown tint and are likely to drop prematurely. Severe infestations for several consecutive years can cause limbs or the entire tree to die.
Siberian elms are most severely attacked by elm leaf beetles and most of the damage is caused by first generation larvae.
Young, developing leaves provide high quality forage for the small beetle larvae. By the time the second generation is feeding, the leaves are mature and there is less damage. Generally, the environmental conditions under which second and third generations develop are not as good as those for the first generation. Elm leaf beetles do not transmit Dutch elm disease.
Natural enemies include birds, toads, diseases and predaceous and parasitic insects. A small wasp frequently kills many pupae. A fungus also kills pupae and adults late in the summer, especially if the weather is humid. Unfortunately, these natural controls are not often sufficient to hold beetles in check, so it is necessary to use insecticide.
Early detection of beetles makes it possible to spray trees before much damage occurs. Examine the undersides of leaves for yellow eggs and young larvae soon after leaves emerge in April. Apply insecticides when most of the eggs have hatched and the small larvae are just beginning to feed. Make sure insecticide thoroughly covers newly developing leaves. It may be necessary to hire a commercial applicator, someone who is properly licensed and equipped, to spray tall trees. Insecticide applications may need to be repeated to control later generations of beetles.
Another approach is to use systemic insecticides, which can be applied as tree implants, soil injections or granules. Systemic insecticides are transported through the tree to the leaves. To control the first generation of beetles, systemic insecticide should be applied in late March or April.
Adult beetles can be excluded from homes by placing tight-fitting screens over windows and doors and closing all other openings. Spraying outside walls and the perimeter of the house with properly labeled insecticides may reduce the adult population in the fall.
If you have specific questions about these insect pest or their control give me a call at 806 6385635.