The Georgia Weekly Weather and Crops Report for the week ending July 23
rd listed the crop as 67 percent setting bolls compared with the 5-year average of 78 percent setting bolls. Recent late afternoon thunderstorms brought temporary relief but sustained moisture is
needed. Thirty-nine percent of the crop is rated poor or very poor due primarily to the ongoing drought. INSECT SITUATION: Tobacco budworm and corn earworm infestations are a mixed bag,
ranging from light to heavy pressure. There is also wide variation in species makeup of the bollworm complex. Threshold levels of stink bugs have been reported from several areas. Aphids are rebounding in some
fields but we would generally expect populations to crash due to the naturally occurring fungus. Silverleaf whitefly has been observed on cotton in the Tift County vicinity and spider mites were reported in southwest Georgia.
Tobacco Budworm and Corn Earworm: There is a wide range in tobacco budworm (TBW) and corn earworm (CEW) populations across the state. Infestations range from light to heavy. There is also much
variability in the species makeup of these infestations. In some areas, it is predominantly TBW or CEW, and in other areas, there is a mixed population. This is not uncommon late in the season as we normally see
overlapping generations of the two species. Species ratio of TBW and CEW is very important when selecting an insecticide, especially in areas where pyrethroid resistant TBW is a concern. We are seeing quite a bit of
variation in species makeup from field to field at this time. Scouts should be observant for moth activity when scouting. Moths are most active after sunset but some can be seen during the day while walking
fields. TBW and CEW moths can be easily recognized. TBW moths are light olive to brownish olive, with a wingspan of about 11/4 inches. Each forewing has three slanted, dark bands. CEW moths are
yellowisholive in color with a dark spot on the forewing. The CEW moth has a wingspan of 1 to 1 1/2 inches which is slightly larger than TBW. "Moth Flushing" counts will give us some idea of which species, TBW or
CEW, is predominant. Bollgard cotton has provided excellent control of TBW, but some treatments for CEW have been needed. On non-Bt cotton, TIMING IS EVERYTHING, especially when TBW is the primary target. Control
of large TBW is very difficult. If pyrethroid resistance is a concern, non-pyrethroid chemistry should be used. If a pyrethroid is used, an ovicide should be added when targeting TBW.
Stink Bugs:
We have received reports from several counties that some fields have reached treatable levels for stink bugs. As corn continues to dry down and be shelled, we may expect to see an increase in stink bug numbers and
damage. Treatment is recommended if 1 stink bug per 6 row feet is found or when 20% internal boll damage is found on quarter sized bolls and stink bugs are observed in the field. Several county agents and consultants
have made observations of higher stink bug numbers on the edge of fields which border peanuts. During 1999, we investigated this edge effect at peanut cotton interfaces and found some interesting results. We collected
bolls from 10 different fields that were bordered by peanuts in Colquitt, Dooly, and Tift Counties. We sampled 30 to 40 bolls from three areas, rows 1-2, 9-10, and 19-20 near the peanut cotton interface. Internal damage
was significantly higher in rows 1-2 (61%) compared with rows 9-10 and 19-20, 27% and 26% respectively. What does this mean? We may expect to see initial field infestations near peanuts. Growers and scouts who are
not familiar with stink bugs and their damage in cotton are likely to see damage in the first few rows near peanuts and thus become more familiar with the damage. There may also be potential to border spray these areas.
Decisions to treat an entire field should be based on a representative sample of the entire field. Recommended treatments for stink bugs include several pyrethroids or the OPs Bidrin or methyl parathion. If larval pests
are also present in a field requiring treatment for stink bugs, pyrethroids would be the treatment of choice.
Armyworms:
Beet and fall armyworm populations remain light, but isolated fields have required treatment.
Aphids: Aphid populations are rebounding in some fields following the crash or epizootic which occurred due to
a naturally occurring fungus. Periodically, we see a rebound in aphid numbers late in the season, but often these populations will crash again from the fungus before populations build to high numbers.
Silverleaf Whitefly: Silverleaf whiteflies have been observed on cotton in Tift and Colquitt Counties during the last two weeks. At this point in time, it is impossible to know if the populations are going to be
economic in coming weeks. However, the potential is there. Rainy periods generally suppress white fly numbers.
Spider Mites: Eddie McGriff, CEC Decatur County, reported a spider mite
infestation in Decatur County. Several products are recommended for spider mites and include Comite, Curacron, Kelthane, Lorsban, and Monitor. Capture should also be recommended for spider mite control and would be a
good option when corn earworm and/or stink bugs are also present in a field. Ovasyn also has spider mite activity. Our threshold is somewhat vague, "apply when mites are spreading". A more defined threshold may be
treat when 50% or more of the leaves 5 nodes down from the terminal are infested. In some situations, spot treatment may be sufficient in infested fields. Good coverage is essential for control, a second application may
be necessary.
INSECT UPDATES: Check the Cotton Insect Hotline (1/800-851-2847) for updates on current insect conditions. The Cotton Pest Management Newsletter is also posted on the Internet at
"www.gaipm.org" and then click on "cotton."
Sincerely,
