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Southeast Missouri Pest Bulletin June 25, 2003

INSECTS & OTHER PESTS
I've received a few calls regarding infestations in corn (European and southwestern corn borers) and cotton (aphids, plant bugs, bollworms) fields. Moth counts (Table 1) in pheromone-baited traps remain low but steady this past week. (MLB)

CORN
Corn Borers: I've only received a couple more calls regarding European (ECB) and Southwestern (SWCB) corn borer infestations in the Bootheel. Looking at the trap counts I suspect we are between generations; therefore, it will be necessary to intensify scouting efforts in the next week or two.

Early detection will be the key to maximizing control of both corn borer species. Both species generally lay most of their egg masses in the ear zone (leaves just below and above the ear plus the leaf at the ear). 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.

COTTON
Crop Report: It's been COLD this year as we have received 514 DD60's since May the 1st; whereas, in 2002 until the present we had received 674 DD60's. Maybe I made a mistake calculating, but the crop looks like it is three weeks behind just as the DD60's indicate. Unfortunately, we can't change the weather; however, we can try to make the best crop possible. Much of the nitrogen has probably leached out so don't reduce the amount of side-dress nitrogen very much. Much of the crop also appears to have a sulfur deficiency, especially on the sandy areas. The crop probably can't stand much water stress this summer; therefore, use a soil probe to keep track of the soil moisture and be prepared to irrigate. Weed control also may be tough due to the crop's short stature and thin stands. A comparison of DD60's for this year versus 2002 is reported in Table 2. (BP)

Aphids: I've received a couple of reports recently that aphid populations are increasing in the region. I'm not surprised as temperatures have risen allowing for improved crop growth. This will enable aphid populations to quickly build in the coming days. Beneficial insect populations also are building, but a combination of different parasitoids and predators are usually required to help keep aphid infestations at subthreshold levels. (MLB)

When scouting for aphids in the field, examine the underside of leaves on five plants at each of 10 locations per field. Aphid infestations can be classified as follows: low (less than 10 aphids per leaf), medium (11 to 25 aphids per leaf) or high (26 or more aphids per leaf). An insecticide treatment is recommended once aphid infestations are medium to high, honeydew deposits are present, and the aphid's natural enemies are absent or ineffective in suppressing these infestations.

A labeled, recommended insecticide should be applied at maximum volume (5 gallons by air and as many gallons as possible with ground rigs) with hollowcone nozzles so to thoroughly coat the plants. If you select one of the neonicotinoid insecticides (Centric, Intruder, or Trimax), avoid the temptation to use lower use rates as it decreases the products' effectiveness and shortens residual control. You are better off banding full use rates NOT decreasing broadcast rates.

Plant Bugs: Tarnished plant bugs are still easy to find on their weed hosts that border cotton fields. As I mentioned last week I strongly recommend that you don't destroy these weed hosts if your crop is producing squares. This will only flare plant bug infestations in your cotton fields.

Bollworm/Budworm: We are still catching a low but steady number of bollworm and budworm moths each week. The highest egg/larval counts I've heard of thus far is around 4% infestation level. As we move further into the season, it will be important to intensify your scouting efforts as infestations may be localized and intense.

STORED GRAIN
Insect pests: With the wheat harvest in full swing, anyone who is storing grain for a long time should consider the following steps to minimize insect damage to your grain. An effective stored pest management program is a 6-step process. 1) Preventing infestations is the initial step. This can be accomplished by inspecting the incoming grain, maintaining storage units in good condition, and adequate ventilation. 2) Sanitizing storage units involves the removal of all old grain from the bins. Never mix new grain with old grain that is potentially contaminated with insects and molds. 3) Proper storage should include spacing pallets 18-inches away from the wall so it's easier to inspect and repair damaged bags. 4) Rotate out old stock to prevent infestations from getting started in the new ones. 5) Proper ventilation is essential to regulate moisture levels in the grain below the recommended maximum levels (ex. wheat - 12%) and to help slow the development of pest populations. 6) Pesticide control should be considered the final step to control infestations.

Insecticides such as Reldan and Tempo can be applied to the inside of grain bins. Grain protectants like Reldan can be applied as the grain is being elevated into the bin. Storcide (a combination of Reldan and Tempo) also can be used but only on wheat to be sold in the United States. In the past malathion has been available to treat stored grain, but it is no longer being recommended. Why? Few malathion formulations are now labeled for such use, insect control has declined, and treated grain has been rejected because of excessive malathion residues. If your management efforts fall short, then fumigation is another chemical option for you. These pesticides should only be applied by certified applicators and when the weather conditions are calm. Bins should be covered and any holes plugged before the bin is sealed. Leave the fumigated grain covered and undisturbed for two to three days.

If you follow the 6-step management plan, you can prevent most pest infestations in your stored grain. Grain that is kept cool (below 55 degrees F) and dry is usually unsuitable for stored grain pests.