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Field and Forage Crops |
The good news is that populations of adult migrating thrips are now declining in South Carolina. The bad news is that thrips will probably be around much of North Carolina for another week or two, if recent history is a guide. Although some areas of the state have adequate to good moisture and good cotton growth, most cotton fields are still on the dry side, translating into less than ideal uptake of insecticides from seed treatments and granular at-planting materials. Plus, adult migration is typically heavier under dry conditions. We now are beginning to see some 5 and 6 true leaf cotton that is out of harm's way.
Although not yet confirmed as western flower thrips, we have had several reports of relatively high thrips levels within 2 to 4 days of a foliar application for thrips. Western flower thrips tend to make up more of the overall thrips population under very dry conditions. However, even under dry conditions, other easier-to-control thrips species (tobacco thrips, soybeans thrips, flower thrips, onion thrips, etc.) collectively constitute a high portion of the population in most cases. Western flower thrips cannot be identified in the field, but instead must be brought back to the laboratory, individually "cleared" in a solution, mounted on a microscope slide and cover slip, and examined under high magnification -- a tedious, time-consuming process. Most often in the field, the first sign of western flower thrips is moderate to high levels of immature thrips following an insecticide applied at a normally recommended rate.
Because western flower thrips are difficult to control with insecticides, apparently only the highest rates of Orthene (0.5 pound of active ingredient per acre or higher) have made much of a dent on these populations. Monitor insecticides has also shown some activity against western flower thrips in other states, but is very expensive at high rates. Other foliar insecticides appear to offer limited activity against western flower thrips. Continuing to treat cotton fields with low or medium rates of Orthene or other materials will likely yield disappointing results where damaging levels of western flower thrips are present. Where possible, a foliar band can help keep the Orthene rate high at a more reasonable cost. Although usually not helpful in most insect control situations, a spray adjuvant may help to reduce thrips levels.
Cotton producers should be encouraged to keep checking cotton fields regularly. If newly-emerging leaves look shiny and relatively straight and immature thrips are at or less than about one per true leaf, or if cotton has reached approximately the 5 true leaf stage with adequate moisture, spraying should not be needed. Also, in general expect thrips levels to be quite a bit lower in strip till or no-till cotton fields, so try to make treatment decisions on a field by field basis.
Robeson, Scotland and Hoke counties:
The initial 2004 cotton scouting school will be held at 9:30 a.m. on June 22 in the Extension Conference Room (Suite 800), County Government Center, 231 E. Cronly Street in downtown Laurinburg. Contact David Morrison (telephone: 910-277-2422; e-mail: david_morrison@nusu.edu), Georgia Love (telephone: 910-671-3276; e-mail: georgia_love@ncsu.edu), or Keith Walters (telephone: 910-671-3276; e-mail: keith_walters@ncsu.edu) for details. Producers, summer scouts, industry personnel and consultants are invited to attend the schools.
Northampton and Halifax counties:
Separate cotton scouting schools will be held in Northampton and Halifax counties on July 22. Details will follow in future issues of the "North Carolina Pest News."
The recent rainfall has made a significant difference in many areas. Not only has the rainfall given the peanut plant a big boost of much needed water, but it has done wonders for insecticide uptake to enhance thrips control. There are plenty of thrips out there and the earliest planted peanuts, as usual, are the hardest hit. Be sure to scout the earliest planted peanuts over the next week to determine how well your at-plant insecticide is working. Remember to look for thrips damage only on the newly-opened leaflets. These leaflets give you the best indication of what is currently happening in the field relative to thrips feeding and insecticide effectiveness.
The dry, hot spring weather has been a perfect environment for spider mites to build up and many have already been seen in cotton, corn, melons and other crops. Spider mites rarely attack small peanuts, but this is a warning to watch for them this year. The potential for spider mite problems in peanuts this year is above normal. Stay away from unnecessary insecticide applications and use the leafspot advisory to help reduce the likelihood of spider mites.
We are also observing quite a few southern corn rootworm beetles this year. It is hard to predict what this means in terms of a potential rootworm problem in peanuts this year. First, the dry weather is working against a rootworm problem in peanuts, but that could always change with some good, well-timed rainfall. Obviously the current dry conditions and the threat from spider mites makes treatment for rootworms a less attractive option. I will keep you updated on both rootworms and spider mites over the next two months as management decisions need to be made.
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 May 28, 2004 by Stephen J. Toth, Jr.