IN THIS ISSUE

· TPMA Website
· Upper Coast IPM Program Sponsors
· Cotton Insect Situation
· Aphid Control In Cotton
· Boll Weevil Trap Counts
· Mexican Corn Rootworm Scouting Program
· Did You Know

TPMA Website

Extension IPM Program newsletters from across the state can be viewed at the Texas Pest Management Association website at www.tpma.org.

Upper Coast IPM Program Sponsors

Cotton Insect Situation

Growth stages of cotton in the Tri-County area of Wharton, Matagorda and Jackson Counties range from first square to one-third grown square.

Aphid numbers were considered light in 90% of the fields that were monitored during the past week. However, overall aphid numbers appeared to be building in numbers as the week progressed. Fleahopper numbers were below economic threshold numbers in 95% of the fields monitored during the past week. Live boll weevils were found in 10% of the fields and boll weevil punctured squares were found in 5% of the fields as well. Bollworm eggs and live bollworm were found in 48% and 43% of the fields, respectively. Egg counts ranged from 2% to 16% and larvae counts ranged from 1% to 9%.

Other pests that were found in low numbers during the past week included loopers in 14% of the fields.

Aphid Control in Cotton

Three species of aphids, or plant lice feed on cotton plants: the cotton aphid, the cowpea aphid and the green peach aphid. Cotton aphids range from light yellow to dark green to almost black. The immature or nymphal stage looks like the adult stage, only smaller. Most adults do not have wings. Cowpea aphids are shiny black with white patches on the legs and are common on seedling plants. Green peach aphids range from pale yellow to green. Winged migrant forms have a yellowish-green abdomen with a dark dorsal blotch. Aphids usually are found on the undersides of leaves, on stems, in terminals and sometimes on fruit. Heavy and prolonged infestations can cause leaves to curl downward.

A (pre-blooming) cotton field should not be treated for aphids unless a heavy infestation has been present for 7-10 days and no signs of their rapid decline exists. A heavy infestation is when aphids exceed 50 aphids per leaf. To determine aphid levels in a field, a total of 60 leaves divided between the top, middle and lower portion of the plant should be sampled from plants across the field. Insecticide control of cotton aphids should be delayed until infestations exceed 50 aphids per leaf. If you think you need to treat after you have had a heavy infestation for the prescribed amount of time, postpone your treatment for another 48 hours and monitor the progress of aphid suppression by beneficial insects. If aphid numbers are down or increased parasitism has occurred reevaluate you decision to treat at this time. Aphid numbers could be headed down in a very short time.

The major beneficial insects, which can control aphid populations, are lady beetles, scymnus beetles, lacewing larvae, syrphid fly larvae, and parasitic wasps. Do not confuse winged aphids with parasitic wasps. In any aphid population winged aphids exist in varying numbers. Aphids are slow

moving, where as the parasitic wasps moves about rapidly. Actually the presence of parasitized aphid mummies is the best way to judge the parasitic wasp activity. Aphid mummies are dead swollen aphids stuck to leaves. The mummies are tan to gold and contain a developing wasp or have a hole cut in the top through which the wasp emerged. If 20% or more aphid mummies are found, you will know that aphid numbers are shortly headed down.

Listed below are the results of two tests that were implemented to evaluate the effectiveness of different insecticides on controlling aphids.

Table 1. Number of Aphids per 5 whole plants, St Joseph, Louisiana, 1999.^a

^a Test conducted by E. Burris, J.K. Sanders and K.E. Williams, LSU Agricultural Center, Northeast Research Station.
^b Treatments were applied with a CO₂ –charged system with 80015 fan tip nozzle (2/row) at 28 psi and 10 gpa total volume on 18 June. Cotton was planted 5 May.
^c DAT = days after treatment

Table 2. Mean number of aphids per leaf on the first fully expanded leaf from the plant terminal, Weslaco, Texas, 2001. ^a

^a Test conducted by A.N. Sparks, Jr. and J.W. Norman, Jr.
^b Treatments were applied on 5/8 by CO₂ pressurized backpack sprayer, 3 TX hollow cone nozzles/row (1 over top, 2 on drops), 40 psi, and 10 gpa total volume.
^c DAT = days after treatment

Boll Weevil Trap Counts

The boll weevil trap line is located in Wharton County on farm to market highway 1162, county roads 442, 422, 409, and 426 and farm to market highway 441 between El Campo and Hillje.

Table 1. Number of boll weevils captured per pheromone trap per month, thirty-two mile trap line, Wharton County, Texas. Texas Cooperative Extension operated traps.

* only two weeks of data

Also, included in this newsletter are the weekly boll weevil trap counts for 2002 from the period March 4th to May 13th. (See enclosed chart included with this newsletter)

Mexican Corn Rootworm Scouting Program

This year thirty-nine fields or approximately 2,625 acres of corn is being scouted by the Upper Coast IPM program. Fields are located in the Burr and Iago areas of Wharton County. This program was implemented in 2001 and we are beginning our second year to evaluate the feasibility of an areawide pest management approach in suppressing numbers of adult Mexican corn rootworm beetles. The premise of this strategy is to kill adult beetles before they lay most of their eggs and prevent economic infestations from occurring if corn is planted in that field the following year. This program is funded by the Texas Corn Producers Board.

Depending on field size, four to twelve Pherocon CRW Kairomone traps are placed in each field. Traps are monitored on a weekly basis for approximately six to seven weeks beginning in the first week of May. Foliar insecticide applications will be made when fields reach treatment thresholds. The treatment threshold for an insecticide application to be made is when a season long accumulation of 100 beetles/trap is reached and when 30% of the females are gravid.

Did You Know

Early History Of The Boll Weevil In Texas: In 1880, Edward Palmer, who served as a Civil War surgeon, was traveling throughout North American collecting plants for the USDA when he encountered an unknown weevil near Monclava, Mexico, about 120 miles southwest of Laredo, Texas. The insect was destroying the cotton crop in this historic growing area by puncturing immature bolls and squares, which caused them to fall to the ground. Palmer sent a few samples of the insect along with some damaged bolls and a letter to Commissioner of Agriculture W. G. LeDuc in Washington, DC.

For five years the samples bounced from desk-to-desk, expert-to-expert, and from continent-to-continent, awaiting positive identification. USDA entomologist C.V. Riley was one of the first to examine Palmer's small weevils, but he was unable to determine their true identity. He turned for help to Henry Ulke, a prominent beetle taxonomist in Washington, but their identity still remained a mystery. Henry Ulke then sent some of the specimens to George Horn in Philadelphia, who in turn sent them on to August Salle, an imminent beetle authority in Paris. Salle, who may have had access to one of the three type specimens located in European museums, finally determined that they were specimens of the boll weevil, Anthonomus grandis Boheman.

The finding was significant for two reasons. First, although the boll weevil had been taxonomically described since 1840, this was the first time that cotton had actually been identified as its host plant. Second, although it was already wreaking havoc in Mexico when Palmer found it, no one imagined that in seven short years it would cross the Rio Grande and change the cotton culture of Texas-and the United States-forever.