Northwest
Plains
Pest Management News
|
|
||
| Volume 1 Issue 7 |
Bailey
and Parmer Counties
|
July
26, 2002
|
|
|
||
|
Northwest
Plains
|
|||||||||
|
Current Crop Conditions Many cotton fields with limited irrigation capacities have started cutting out. Many more are very close to cut out. Without rain soon there is a possibility of loss of existing fruit. On the other hand fields being pushed for maximum yield with plenty of irrigation need to be monitored for excessive vegetative growth. Four to five nodes above white flower on August 10th to 15 th would be ideal. Insect pressure has been relatively light this past week in most area cotton. There are a few fields in southern Bailey County that have boll worms in numbers that justify treatment. A few area cotton fields are showing symptoms of bacterial blight and or verticillium wilt. A few earlier planted black-eyed pea fields are showing signs of a bacterial leaf disease. It is to early to start losing leaves. Stink bugs have also been observed in black-eyed peas as well as pinto beans. A few corn ear worms are showing up in very low numbers. Daily Water Requirements
|
Southwestern Corn Borer Most corn has been treated for southwestern corn borers. Fields that have not been treated need to be monitored very closely. Check for egg masses to determine the potential infestation and the correct timing of insecticide application. Insecticide should be applied when 20 to 25 percent of the plants are infested with eggs or newly hatched larvae. Spider mites are simmering in most corn, hopefully the corn borer treatments will not flair them. Keep a close eye on the mites, especially if a corn borer treatment that had no mite activity was applied. Plant Bugs A few fields had to be treated for lygus bugs last week. The threshold for lygus once cotton gets into bloom is two per three row feet based on the beat cloth sampling method. Combine this threshold with a damage assessment to determine the need to treat. Damage to squares is characterized by yellow |
|||||||||||||||||||||||||||
|
1
|
|
staining before it drops off. Damage to blooms results in black anthers (the part of the bloom that contains the pollen) and puckered areas in the petals. Boll damage is often characterized as small black spots or small sunken lesions. The black spots will extend through the boll wall and cause stained lint. Bollworms/Headworms Corn
earworm moths lay eggs on leaves or grain heads of sorghum. Newly hatched
corn earworm larvae are pale in color and only 1/8 inch long. They grow
rapidly and become variously colored, ranging from pink, green or yellow
to almost black. Many are conspicuously striped. Fully grown larvae
are robust and 1 1/2 to 2 inches long. Corn earworm larvae feed on developing
grain. Small larvae feed on flowering parts of the grain head at first,
then hollow out kernels. Larger larvae consume more kernels and cause
most damage. The last two larval stages cause about 80 percent of the
damage. Frass is |
Because many young headworm larvae die naturally, do not apply insecticide until they are at least 1/2 inch long. The economic injury level is about 1 to 2 larvae per grain head of commercial sorghum. Fewer larvae per grain head may justify treatment on sorghum grown for seed because of the higher per-acre value.
Monti Vandiver |
||||||||||||||
| Educational programs
conducted by Texas Cooperative Extension serve people of all ages regardless
of socioeconomic level, race, color, sex, religion, handicap or national
origin. The information given herein is for educational purposes only.
References to commercial products or trade names is made with the understanding
that no discrimination is intended and no endorsement by Texas Cooperative
Extension is implied.
The Texas A&M University System, U.S. Department of Agriculture,
and the Commissioners Courts of Texas Cooperating
|
|
2
|
common in infested grain heads, on tops of upper leaves and on the ground
under p lan t s . Natural mortality of small corn earworm larvae is
normally very high. Begin inspecting sorghum grain heads soon after
flowering and continue at 5-day intervals until hard dough. To examine
grain heads for headworms, shake randomly selected grain heads vigorously
into a 5-gallon bucket, where larvae can be seen and counted easily.
This "beat-bucket" technique permits detection of even small
larvae (less than 1/4 inch) commonly overlooked during visual inspection
of the grain head. Inspect at least 30 grain heads from a field to ensure
reasonable reliability of sample size. Sample at least one grain head
per acre in fields larger than 40 acres. 
