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Field and Forage Crops |
Although a given cotton aphid population typically causes far more economic damage on drought-stressed cotton, initial aphid build-ups are more likely in wet weather. In many cotton fields throughout North Carolina, small cotton aphid colonies are present on most plants, perhaps more so than in recent years. Although these widespread, low-level populations are not an economic concern, they may indicate a greater potential for outbreaks in the coming weeks, especially if the onset of pyrethroid insecticide spraying for bollworms or stink bugs coincides with moisture-stressed plants. We received one report from Halifax County of 200 acres treated (numerous large colonies in small cotton with few mummifying parasites, no fungus and minimal beneficials). If other treatable cotton aphid levels develop with the next two weeks or so, the aphid-parasitic fungus Neozygites fresenii may not arrive in time to reduce or eliminate aphid levels as is normally the case from late July on. This would appear be a good year for scouts to record cotton aphid information such as the percentage of infested plants, aphid damage rating, soil moisture, colony size, and presence of aphid mummies or the fungus.
Last week, I mentioned that plant bugs had reached very high levels on weeds and other hosts surrounding cotton fields. Although our recent rain may have helped hold most adult plant bugs on these lush-growing weed hosts, we have a very high probably of returning to drier weather. Moderate to heavy levels of adult plant bugs migrating into cotton could be the result. Square retention counts and sweeping for adults when square retention counts drop to less than 80 percent is strongly recommended this year.
Due to our cool rainy weather and a generally late corn crop, it appears that the major bollworm moth flight will be somewhat lighter and later than in 2002. However, our cotton crop is also shaping up to be on the late side, and will probably remain susceptible further into the growing season (barring drought conditions that could push the crop toward premature cutout). Oddly, our producers suffer almost as much boll damage by season's end during these lighter bollworm years, often due to delays in initiating treatment with insecticide.
A Spanish version of the Cotton Insect Scouting Guide is now available at the Cotton Insect Corner web site.
Nash and Wilson counties: July 21, 2003 at 4:00 p.m. in the Nash Agriculture Center Auditorium in Nashville. Contact Charlie Tyson (e-mail: charlie_tyson@ncsu.edu; telephone: 252-459-9810) or Norm Harrell (e-mail: norman_harrell@ncsu.edu; telephone: 252-237-0114) for details.
Halifax County: July 23, 2003 at 9:30 a.m. in the Halifax Agricultural Center in Halifax. Contact Arthur Whitehead (e-mail: arthur_whitehead@ncsu.edu; telephone: 252-583-1683) for details.
Northampton County: July 23, 2003 at 1:00 p.m. in the County Administration Building in Jackson. Contact Craig Ellison (e-mail: craig_ellison@ncsu.edu; telephone: 252-534-2711) for details.
The thrips populations in peanuts are showing signs of decline and in areas with good soil moisture, the warmer temperatures have brought on a rapid flush of growth. We are starting to see plants with symptoms of tomato spotted wilt virus. It is still too early to say much about the level of virus we will encounter this year. I still think it will be a little less than what we saw last year, but I could easily be proven wrong. Whatever happens, do not waste time and money on the use of foliar insecticides for thrips control at this time of year. Such treatments have not been shown to provide any significant reduction in the virus and could encourage spider mite outbreaks.
If you are going to treat for southern corn rootworm, this is the time to do so. Use the rootworm advisory to help make good decisions about treating with insecticide. We are seeing a few leafhoppers in peanuts, so be sure and watch for them as well. It will not be but a few weeks, when worms start to become a possibility in peanuts. I do not see any reason to think that we will suffer another beet armyworm outbreak this year. It is still important to maintain a good scouting program in peanuts over the next two months for worms and spider mites.
Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age or disability. North Carolina State University, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.
Last modified on July 7, 2003 by Stephen J. Toth, Jr.
