Southeast Missouri Pest Bulletin No. 4, June 10, 2004

INSECTS & OTHER PESTS

There are few new things going on this week on the insect front. I've been receiving reports about several crop pests (ex. plant bugs, spider mites, thrips in cotton; Southwestern corn borer in corn) being active in southeast Missouri. The latest moth trap captures for the crop pests that we're monitoring are reported in Table 1. (MLB)

ALFALFA

Soldier Beetles: Jeff House, MU Regional Extension Specialist, had an interesting find yesterday when he reported seeing large numbers of soldier beetles in an alfalfa field. This particular soldier beetle isn't a pest, but is highly beneficial since they readily feed on aphids and other soft-bodied insects. Adult soldier beetles are very common on foliage and flowers where they feed on pollen and other insects. Again, soldier beetles are not pests and plants should not be sprayed where you see these beneficial insects.

CORN

Southwestern corn borer (SWCB): David Guethle, MU Regional Extension Specialist, reported moth flights decreased this past week in Stoddard County. This is a good indication the first generation moth has peaked, and I'd look for the second one to peak in early-July. Keep in mind this second generation of SWCB has the greatest negative impact on yields in non-Bt corn fields. I also received a report from Brad Williams of Cardwell who found up to 5% infestation levels in some of his fields, with isolated 'hotspots' of 70% infestation levels within those fields. As I mentioned last week, granular formulations are usually more effective for whorl stage corn, whereas, liquid formulations are best once corn plants begin to tassel. The recommended MU action threshold for SWCB is 25% of the plants infested with egg masses and small larvae.

COTTON

Thrips: I've received a few more reports of continued insecticide oversprays for thrips in late-planted or replanted cotton fields. I wouldn't expect thrips pressure to decrease anytime soon in those fields since the wheat harvest is in full swing. As I said last week I still have not received any samples to verify that we have western flower thrips in the area, but I wouldn't be surprised if some are present in Missouri cotton fields. If you have a confirmed identification that western flower thrips are present, methamidophos (Monitor) at 16 fluid ounces of formulated material per acre is recommended for control of this species. Research conducted at other universities indicates two foliar applications (5 to 7 days apart) are required to control western flower thrips infestations.

Aphids: I've received a couple of reports that within the past two weeks a few fields were treated for aphid infestations. I also recommend that you closely monitor any fields that have been treated multiple times for thrips or were treated with acephate. Why? Aphid populations can rapidly increase where their natural enemies have been reduced or eliminated with prior insecticide sprays.

When scouting for aphids, 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 usually recommended once aphid infestations are medium to high, honeydew deposits are present, and/or 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 of the aphids. If the cotton isn't too big and you have the right equipment available, you are better off banding full use rates NOT decreasing the broadcast rates.

Plant Bugs / Cotton Fleahopper: Phil Gurley reported he has recommended treating some of the older cotton that he scouts for plant bugs (mainly tarnished species). He also observed a moderate number of cotton fleahoppers in one field. Plant bugs will most likely move into earlier planted fields and/or those where alternative weed hosts (ex. plains coreopsis) are very abundant within and around the fields. Just remember that plant bugs can be very erratic when infesting fields, and they will move in and out of fields to feed on the most succulent plants available in the area.

The initial MU action threshold for plant bugs is 6-8 per 100 row feet during the first week of squaring cotton, and 8-10 per 100 row feet during the second week of squaring. In recent years several new insecticides have been introduced for plant bug control; therefore, you now have more options for controlling plant bugs and not trigger outbreaks of other pests like aphids with older compounds such as acephate.

Spider Mites: I've also received reports that spider mites are still being treated in a few locations this past week. Just remember that spider mites can be easily spread across fields by field equipment, people, weather, and wildlife from heavily infested areas (i.e. border vegetation) to other parts of the field. The recommended action threshold for insecticide oversprays is 50% of the plants infested and mite populations are increasing. Miticide treatments should be applied at high volumes and pressures so to thoroughly coat the underside of leaves, and a second treatment 7-10 days later is usually necessary to kill any mites hatching from their eggs.

Table 1. Pheromone moth counts as of June 9th.

Comments: Number of days refers to the last time the trap was checked since the last reporting date.CEW = corn earworm / bollworm, ECB = European corn borer, SWCB = SW corn borer, TBW = tobacco budworm

2004 Missouri Rice Farm Field Day Tuesday, August the 24th

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The University of Missouri does not warrant products mentioned in this publication. The use of a trade name does not constitute recommendation of one product over other (generic) products of a similar chemistry.