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Field and Forage Crops |
Although stink bugs do not seem to have come out of the gate as strongly as last year, I think we can count on at least a moderate stink bug year in many areas of the state. Remember that this year's cotton crop is off to a much later start than in 2004, and late maturity may become a significant issue this year unless we are blessed with timely rainfalls for the remainder of the season and good harvest conditions. This translates into taking stink bugs and bollworms seriously. For stink bugs and plant bugs, within a week to 10 days after bloom initiation a sample of 25 to 50 quarter-sized bolls should be selected from representative areas of cotton fields and either crushed or cut open with a knife an examined for internal stained lint and/or warts on the inside surface of boll walls. Cutting open bolls is critical to responding to stink bug damage in a timely fashion and alternatively to the avoidance of unnecessary insecticide sprays.
All our light traps this season are being checked for both green and brown stink bugs, with green stink bugs being more readily attracted to these traps. Stink bugs caught in light traps will likely reveal much more localized information than is the case with corn earworm moths whose numbers are often a good indication of the timing and intensity of these flights over larger areas. In the Laurinburg light trap, the July 22 green stink bug count was 108, versus 0 in Onslow County. This dramatic difference in stink bug levels is more likely due to differences in the immediate surrounding crop and non-crop vegetation in the two locations, as opposed to a widespread trend. A graduate student, Eric Blinka, is presently evaluating the possible relationship between landscape and vegetation features and stink bug levels with an eye toward being able to assign cotton fields into stink bug risk categories.
The beginning of our major bollworm moth flight must be just around the corner in Scotland and Robeson counties. The July 22 light trap counts of bollworm moths in Scotland County were 6, 25, and 11 in Gibson, Johns, and Laurinburg, respectively (very low numbers for this time of year). We will almost certainly have increases in moth counts to report on the July 27 Cotton Insect Hotline Teletip (1-800-662-7301). The same potentially late crop considerations that applied to stink bugs on Bt cotton will apply to bollworms on conventional cotton. That is, we may need to be somewhat more protection oriented with what could be a shortened boll production period. So be alert to the beginning of the moth flights, close down the scouting frequency accordingly when that time comes, and respond to threshold levels of bollworm eggs on conventional cotton.
In general, spider mites levels seem to have declined significantly during the past week, in part to moderate to excessive rainfall over much of the eastern part of the state. Several areas are dry, however, with small cotton blooming out the top in parts of Northampton County on July 21, but with surprisingly low levels of spider mites.
Cotton aphid levels are at least moderate in some areas, with several cotton fields treated this past week. Before treatment, be sure that all of the following criteria have been met: 1) aphid levels both high and causing "drooping" on most plants in the field; 2) honeydew easily seen on most plants; 3) little or no evidence of the parasitic wasp mummies; and 4) complete lack of the aphid fungus. Following a cotton scouting school on July 21 in Halifax County, I was in a cotton field with the remnants of an aphid infestation. Both aphid mummies and the fungus were present. By next week, we should have a greater appreciation of how this year's stink bug and bollworm levels are shaping up.
Quite a lot is happening in peanuts these days. The hot weather has had numerous impacts. First, it has created a few spider mite problems and I expect more to follow. Growers should be sure to watch fields carefully, especially those treated for corn rootworms. If growers are planning to make an application of insecticide for rootworms, the deadline for effective timing is rapidly approaching. Research has shown that applications after August 5 are often much less effective.
The hot weather has resulted in the symptoms of tomato spotted wilt virus occurring a lot more readily. It is hard to determine if there is more virus in peanuts this year as compared to the past two years. The weather this year has been hotter which stresses the plants more. This often gives us more symptoms in the field.
Keep in mind that worm season in peanuts is rapidly approaching. Treat only when the threshold of four worms per row foot is exceeded.
This is what all tobacco growers have been waiting for . . . blue mold on cultivated tobacco was first reported in North Carolina in 2005 on July 15 in Reidsville, North Carolina. Two days later, this disease was also reported in Leicester, North Carolina (northwest of Asheville); however, this infestation is probably older due to the severity of symptoms. This foliar infection is characterized by round, yellow spots with gray or bluish-gray mold on the undersides of leaves. If growers have yet to treat their tobacco, tank mixes of Acrobat 50WP and Dithane DF Rainshield should be applied weekly until topping. Because Acrobat MZ is no longer manufactured and has been replaced with Acrobat 50WP (dimethomorph only), Acrobat 50WP must be tank mixed with a protectant -- the only option being Dithane DF Rainshield. Mixing ratios for Acrobat and Dithane DF Rainshield are listed in the 2005 Burley Tobacco Production Guide. Actigard 50WG also is effective against blue mold and should be used preventively. It has a narrow window of use, starting when tobacco is 18 inches high or approximately five weeks after transplanting and up to topping. Because Actigard 50WG is a systemic product that induces the plant to resist blue mold beginning four days following application, it should not be used for the first application as blue mold is in North Carolina NOW. However, it can be used after an initial Acrobat application. The induced resistance will persist for approximately 10 days, and Actigard 50WG can be reapplied to continue protection until topping.
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 25, 2005 by Stephen J. Toth, Jr.