Southeast Missouri Pest Bulletin No. 9, July 15, 2004

INSECTS & OTHER PESTS
Insect activity has picked up this past week in southeast Missouri. I've received reports about the following crop pests (ex. corn borers in corn; bollworms, plant bugs, spider mites, stink bugs in cotton) being active in the Bootheel. The latest moth trap counts for the crop pests that we're monitoring along with area consultants are in Table 1. (MLB)

CORN
Corn Borers: Based on this week's SW corn borer trap counts at Portageville, we're definitely in the midst of the second generation moth flight. Any fields with non-Bt corn should be monitored for infestations because this generation's feeding damage can lead to the greatest yield losses. The MU action threshold for SW corn borers is 25% of the plants infested with eggs and live larvae.

COTTON
Sulfur Deficiency: We've recently received several calls about yellow cotton. With the wet weather, sulfur deficiency has been common this year. The typical symptom is yellowing of the new plant growth; whereas, nitrogen deficiency is yellowing of the old growth. A petiole test along with a soil test can determine if sulfur deficiency is the root of the problem. Results from the MU Delta Center Soil Test Lab can be obtained within 24 hours! A foliar application of fertilizers containing sulfur should solve this problem. Between growing seasons a soil application is most advisable. (BP)

Insecticide Product Update: I recently received some product information from AMVAC regarding the legal use of Bidrin (dicrotophos) for 2004. Key application points on the current label are: 1) Bidrin can still be aerially applied, 2) Bidrin may be applied at rates up to 8 oz /A, and 3) Bidrin may be applied a maximum of 3 times this season. (MLB)

Bollworm/Budworm: We continued to catch to a high number of bollworm moths in our pheromone trap at Portageville this past week, and Phil Gurley had a couple of sites with some substantial counts as well. But, the moth counts were again very variable across locations as listed in Table 1. Any fields that are lush and flowering plus have non-Bt or Bollgard I varieties should be closely monitored for eggs and small larvae. The recommended MU action threshold for bollworms and budworms in non-Bt cotton is to treat before 10% or more of the plants are infested with small larvae (less than ¼-inch in length). In Bt cotton fields a recommended threshold for bollworm control is to apply a foliar treatment when 4 or more larvae (greater than ¼-inch in length) per 100 plants are present.

Plant Bugs / Cotton Fleahopper: Based on comments that I received from several different people, there doesn't appear to be much of a letup in plant bug infestations. A couple of experienced consultants are reporting they are spraying for plant bugs practically on a weekly basis. This is reminiscent of the days that boll weevils were our main problem! Unfortunately, plant bugs have many more hosts than boll weevils; thus, we have a greater pool of plant bugs migrating into cotton from other crop and weed hosts.

Spider Mites: Matt Robbins reports this has been his major pest problem this past week. If hot, dry conditions continue to persist, there's the potential for a rapid increase in spider mite infestations. To maximize control of mite infestations, choose an appropriate miticide and apply it at high volume and pressure so to thoroughly coat the plant.

Stink Bugs: Both Michael Johnson and Matt Robbins report finding stink bugs, primarily green stink bugs, in fields that they scout. In Mr. Johnson's case, the cotton fields were close to corn. This is a common occurrence of how corn can influence stink bug infestations in cotton as well as grain sorghum and soybeans. Since stink bug infestations can be very sporadic in cotton, careful scouting is important for detecting the insects plus their feeding damage.

To scout for stink bug infestations, use a drop cloth or take beat-net samples at 10 different locations in a field. Since stink bug eggs are laid in masses, infestations are rarely uniform across a field. Unlike most pests that infest cotton fields, stink bugs can damage even relatively mature bolls (outer damage - small, sunken, black spots; inner damage - seeds discolored and 'warty' growth on inner boll wall). Thus, it's just as important to cut open a few bolls to check for signs of feeding damage (stained lint and discolored seeds) as finding the stink bugs themselves. Insecticide treatments are recommended once stink bug infestations reach two to six stink bugs (large nymphs and/or adults) per row feet, OR when 20% of medium-sized bolls display internal signs of damage and stink bugs are observed in the field.

Recognizing whether brown or green stink bugs are more prevalent is important because it will influence which insecticide you should apply. Since brown stink bugs are more tolerant to pyrethroid insecticides than green stink bugs, it's recommended that you use an organophosphate (ex. Bidrin, Orthene) if brown stink bugs are most prevalent in the field.

RICE
Rice Stink Bug: Nothing new to report on rice stink bug infestations. Just remember to closely monitor any fields where the panicles are emerging for rice stink bugs. The MU action threshold is to treat when stink bug populations average 5 or more per 10 sweeps during the first two weeks of heading and 10 or more per 10 sweeps during the second two weeks of heading. At this time of the growing season, I'd recommend applying a pyrethroid (Karate, Mustang Max, Prolex), as these insecticides will give you the longest residual control of the insects.

ANNOUNCEMENT Dr. Ray Nabors, Coordinator of MU Southern Telecenter, is pleased to announce that courses will be offered beginning this August for a Masters of Science in Agriculture through the MU Delta Center's Southern Telecenter. This degree program is cooperative effort between Arkansas State University (ASU) and the MU Southern Telecenter. For more information on this program contact Dr. Nabors (dctcrc@missouri.edu, 573-379-5609) or Dr. Cal Shumway at ASU (cshumway@astate.edu, 870-972-2087).