Texas Agricultural Extension Service

Volume XXVII No. 12 May 18, 2001 GENERAL SITUATION: The weather this week was hot and dry. Most field work observed was cleaning field margins and a small amount of cultivation. Most fields were laid by and waiting for the next rain or irrigation. Already some fields need moisture and quickly since there is no subsoil moisture this year. Blooms in the top of cotton and sorghum heads appearing to be drying too rapidly were observed this week. Insect activity was lighter this week than last except for boll weevils in cotton. Aphids Take a Nose Dive Aphids were on the decline in most fields this week. Fields which last week showed heavy infestations and some honeydew had fewer aphids this week, in most situations. Beneficials including lady beetles, syrphid fly larvae, aphid parasites and minute pirate bugs took a big chunk out of the aphid populations. Increased aphid mummies were present indicating increased aphid parasite activity. Also, the aphid-killing fungus (probably Neozygites fresenii) that tends to increase when aphid populations are high and area wide moisture is abundant (even if it is temporary), was in evidence this week. Large and increasing numbers of dead aphids had grey-colored fungal growth on their bodies in cotton fields scattered across the LRGV. Between the beneficial insects and fungus, the aphid populations appeared to be in a rapid, major decline in most fields. Some fields still required treatment for aphids because of overwhelming numbers this week, but most were much improved compared to last week. But, keep looking at the fields. Aphids and beneficials don't read books and therefore may not do what they are supposed to. Scouting will tell. Weevil Punctures Going Up Boll weevil infestations increased slightly this week. Reports from the Delta Lake area and Santa Rosa areas indicated weevil punctures being easily found on the ground in a few fields where overwintered weevil applications had not been made. The recently found infestations required the first in-season insecticide application for weevils this year. Reports indicated that neighboring fields which were treated for overwintered weevils had yet to see any significant number of weevil punctured squares. Weevils could be tough customers again this year, but so far, the overall picture indicates that they are in lower numbers than at this same time last year. Let's hope they stay that way. Boll weevil trap numbers remained low except at the two sites which have been high since the first week of trapping (See attached graphs). They are trap sites number 17 north of Edcouch on FM 1015 and number 63 just west of Santa Rosa on S.H. 107, near the sugar mill. Any cotton in those two areas should be checked frequently for weevil activity. Fleahoppers Up/Down Cotton fleahoppers were in lower numbers in some fields and higher in others based on reports to us this week. Insecticide applications for the fleahoppers apparently were successful

Educational programs conducted by the Texas Agricultural Extension Service serve people of all ages regardless of socioeconomic level, race, color, sex, religion, disability or national origin.
The Texas A&M University System, U.S. Department of Agriculture, and the County Commissioners Courts of Texas Cooperating.

PEST CAST continued

in most fields. Some adults were noted in a couple of fields following treatments a week ago. But, nymphal stages were much lower in most fields. Counts of fleahoppers reported to our offices this week ranged 0 to 30 per 100 plants.

Beet Armyworms Lower

Captures of beet armyworm (BAW) moths in traps were lower this week than last week. The highest moth count was at Weslaco, but was low by previous years' standards. Field counts of BAW larvae this week were also lower than last week. Many parasite (Cotesia spp.) cocoons were reported, especially in Willacy county. Less than one BAW larvae per field was reported this week. Since times do change and BAW could re-surge as a significant pest before this season is completed, all growers should continue to monitor for BAW Stay alert.

Beet Armyworm Trap Records

Garden Webworms

While some fields of cotton are beginning to look like flower gardens due to blooming in the top, garden webworms are finding some cotton fields more than a little tasty. We had several reports of garden webworms feeding in cotton this week. Garden webworms are pale yellow-green with dark spots on their bodies and have a brown head. They range in size from 1/16th inch to slightly over 1 inch. When disturbed, the webworms become very agitated and may even leap off the plant. They seem to have the ability to move just as fast backwards as they can forwards.

They generally feed around the square taking off the calyx of the square, but not actually penetrating the square itself. Webworms usually spin a web inside the square bracts around the square and feed under the web. Feeding of the kind that webworms normally do on cotton should not cause square shed, but if the crop is already under drought stress, the plant may decide that the little feeding on the square edges is excuse enough to dump the square. Webworms normally are at low levels in any given field and do not damage the crop. However, one field north of Hargill was reported to have about 8 garden webworms per 100 plants. While no squares were reported to have been holed, a couple of squares were found on the ground with the webbing intact.

No threshold exists for garden webworms simply because they are not considered a pest, even though they are found

PEST CAST continued

in very light numbers most years in the LRGV. But, caution should lead to increased scouting in fields where the webworms are in the heaviest concentration. Probably, any insecticide used for worm control would kill webworms, but should not be used just because a few have been found in the field. Carefully evaluate the actual cause of any fruit loss before deciding that insecticide is needed.

Greenbugs Staying Put

Greenbugs were continuing to be found in some sorghum fields this week. There were a couple of reports this week indicating heavy damage from greenbugs in at least two fields. The reports also indicated that some insecticide applications for the pests were made this week, but overall, greenbug numbers were not yet noted to be causing too much concern. Beneficials, as in cotton, were heavy in most fields and were taking a good toll on greenbugs and other aphids. Check each field for actual damage and beneficial activity before making any insecticide applications.

Greenbugs Being Typed

Early last week, we sent some greenbugs to have them tested to determine which biotype we have in the LRGV. The reason for typing the greenbugs is that greenbug-resistant grain sorghum varieties only protect against certain types of greenbugs. For instance, type E resistant sorghum will be protected from type E and earlier greenbug types. If type I greenbugs show up, then the type E greenbug resistant sorghum may not protect the field from type I greenbugs. Serious damage could occur unless insecticide is used. One of the reports we received this week was that greenbugs caused significant damage to a field of type E greenbug-resistant sorghum. The samples we sent will have to be reared into slightly larger colonies so that they can be

properly tested. But, when we get the result we will relay them to you.

Sorghum Midge Reported

Sorghum midge were reported in very light numbers in one field near Weslaco this week. However, all other blooming fields of sorghum examined this week had zero midge. The presence of midge, even in one field, probably indicates the normal increase that we expect at this time of the year. Therefore, everyone should be alert for increases in midge to economic levels within the next two to three weeks. The attached table shows the midge treatment thresholds and insecticide suggestions for sorghum midge from the Texas Agricultural Extension Service publication number B-1220, Managing Insect and Mite Pests of Texas Sorghum.

Research we have conducted in the LRGV shows that when midge reach economic levels, insecticide applications will be necessary to prevent the near complete loss of yield. Even though the cost of control maybe higher than the return, no insecticide applications likely could mean the complete loss of the crop and no return at all.

PEST CAST continued

Remarks
Cyfluthrin. If one or tow applications are made, green forage may be fed or grazed on the day fo treatment. If the three applications are made, allow at least 14 days between last application and grazing.
Cyahlothrin. Do not graze livestock in treated area or harvest for fodder, silage or hay.
Parathion. Aerial application only. Do not substitute methyl parathion.

THE INFORMATION GIVEN HEREIN IS FOR EDUCATIONAL PURPOSES ONLY. REFERENCES TO COMMERCIAL PRODUCTS OR TRADE NAMES ARE MADE WITH THE UNDERSTANDING THAT NO DISCRIMINATION IS INTENDED AND NO ENDORSEMENT BY THE COOPERATIVE EXTENSION SERVICE IS IMPLIED.

Posted at this web site by:
texagnet Internet Services.