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Southeast Missouri Pest Bulletin June 18, 2003

INSECTS & OTHER PESTS
With temperatures finally starting to warm up, insect pest activity also has picked over the past few days. I've received a few calls regarding infestations in corn (European and southwestern corn borers) and cotton (thrips, aphids, bollworms) fields. Moth counts (Table 1) in pheromone-baited traps remain low but steady again this past week for several crop pests. (MLB)

CORN
Corn Borers: I've received several calls the past few days about increased moth and caterpillar activity by both European (ECB) and Southwestern (SWCB) corn borers in the Bootheel. The early indications are we may be seeing greater borer activity this year compared to the past few years. Bill Emerine reported last Friday he caught approximately 275 SWCB moths in a light trap near Parma. Jeff House, MU Regional Agronomy Specialist in New Madrid County, said he was seeing a lot of ECB moth activity near the Mississippi River levee, and in a field near Portageville he observed ECB larvae feeding in the upper and lower ends of the stalk. On Monday, Brian Williams of Cardwell reported he had a field with 80% of the plants infested with SWCB larvae.

Any non-Bt corn fields should be carefully scouted for corn borer egg masses and hatching larvae. Early detection is the key to maximizing control of both corn borer species. The egg masses of both species look like overlapping fish scales. The larvae will hatch within five days once ECB eggs have a yellowish appearance and SWCB eggs have three red transverse bars. As a reminder ECB larvae initially have a whitish coloration before turning light tan to a pinkish gray with rows of brown spots; whereas, the summer form of SWCB larvae are initially a reddish color before turning white with black spots. An increase in temperatures usually means larvae will feed for a shorter period of time on the leaves before boring into the stalk.

The recommended action threshold for ECB is 50% or more of the plants infested with egg masses and small larvae; whereas, with the SWCB it's 25% infested with egg masses and small larvae. Additional information for both of these corn pests is available in MU guidesheets G7111 (SWCB) and G7113 (ECB). You can obtain these and other crop pest guidesheets at your local MU extension office, here at the MU Delta Center, or from MU Extension Publications (800-292- 0969).

COTTON
Crop Report: We have received another 94 DD60's this past week; whereas, in 2002 we had received 119 for the same week. In effect we lost a day this week. With the low temperatures it's not surprising that the crop is slowly developing this year. A comparison of DD60's for this year's crop versus the 2002 one is reported in Table 2. (BP)

Boll Weevils: I spoke with Dewey Wayne King, Program Manager for Missouri Boll Weevil Eradication Program, yesterday, and he had the following comments to make about the boll weevil situation. 1) A majority of the weevils being caught in traps are in southern Dunklin and Pemiscot Counties near the Arkansas state line. 2) Most acres that will be treated this week will be in southern Dunklin County. 3) A summary of the program's trap counts for June 5-11 can be found in Table 3.

Thrips: Normally, we would be past the time to be worrying about thrips and their feeding damage; however, this hasn't been a normal growing season. You should continue monitoring any cotton that isn't past the 4th true leaf growth stage for any infestations and damage. Again, we can ill afford any delay in this year's crop. With wheat being harvested this week, I definitely expect more thrips will invade nearby cotton fields. Foliar insecticide sprays should be triggered once an action threshold of 1 thrips per plant is present in the field. (MLB)

Plant Bugs: Populations of tarnished plant bugs continue to build in weed hosts bordering cotton fields. My students and I have sampled patches of daisy fleabane, plains coreopsis, and vetch near Portageville and we found approximately 50 tarnished plant bug adults and nymphs per 25 sweeps. A management practice that I've recommended before is to mow down these weeds IF your cotton has not begun putting on squares. On the other hand, if squares are being produced it's best NOT to destroy these weed hosts to prevent flaring plant bug infestations in the cotton.

Bollworm/Budworm: As I mentioned earlier bollworm and budworm moth counts have been declining; therefore, we may be between generations at this time. I'm still receiving reports of bollworm / budworm egg lays in pre-squaring cotton. Ed Kowalski reported he observed 3% infestation levels this past week in 10th-11th node cotton. Generally, I don't recommend spraying for these pests this early unless they are destroying the terminals. I would suggest overspraying with an insecticide that has larval and ovicidal (egg) activity if 20% or more of the plants have terminal damage.

FIELD DAYS
The annual weed is set for July the 17th from 9:30 through 12:00 at the Delta Center Lee Farm located 8 miles southeast of Portageville at the intersection of highways T and TT. This is your chance to see the latest weed control technology in corn, cotton, rice and soybeans at one time. Highlights on the tour include stops for Liberty Link and Roundup Ready Flex cotton and a wide range of no- till burndown studies including horseweed control. The tour is free and open to the public; however, we ask that interested persons preregister by calling the Delta Center at 573-379-5431. Continuing education credit for Certified Crop Advisors should be available. Additional information is available on the following website: http://www.psu.missouri.edu/deltaweeds/. (AK)

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