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From: Jack S. Bacheler, Extension Entomologist
As sometimes happens, the general appearance of our cotton crop seems to have actually worsened this past week, perhaps a combination of our cool night time lows, the rough start and heavy thrips pressure. I had thought by this time, cotton would have taken a strong turn for the better. The cotton seedlings in this photo are probably pretty typical. This cotton looks more like our untreated checks in most years, but is, in fact, seedlings treated with a foliar spray of Orthene at 0.3 pounds of active ingredient per acre behind 5.5 pounds of Temik 15G at planting.
In some cases, we need to be more patient. With our cool nights, cotton may take as long as 5 or 6 days, or more, to show visibly improved growth due to thrips control. Some poor looking cotton revealed immature thrips levels of less than one per plant. In other cases, we have found 2 to 4 immature thrips per plant just 4 or 5 days after being treated with a moderate to high rate of Orthene (0.37 to 0.5 to ounces per acre following either a seed treatment or Temik). Control difficulties such as this are sometimes associated with western flower thrips, a more difficult to control species. However, an early inspection of a small sample revealed mostly easier to control tobacco thrips.
Be sure to inspect cotton seedlings for immature thrips with a hand lens or beat seedlings onto a flat white object to determine whether the thrips are present at high enough levels to justify treatment. An average of 1 immature thrips per plant per true leaf present is a good point of reference.
As mentioned in last week’s North Carolina Pest News, for cotton replanted from this time on, a seed treatment alone or Temik 15G at the lower 3 pound rate should not require a foliar insecticide treatment for thrips. Don’t leave out this protection, however, as late May planted cotton at our latitude should not be exposed to stresses that might cause additional delays.
With the high percentage of our cotton acreage being treated for thrips, some 2 or occasionally 3 times, spider mites may again become a problem on some of this acreage, more so in the case of these applications following the seed treatments Gaucho Grande, Cruiser or Avicta than following Temik. So watch for spider mites.
From: Gerald J. Holmes, Extension Plant Pathologist
On May 23, 2006 an outbreak of potato late blight was reported from south central Washington County, North Carolina. Cool spring weather has undoubtedly contributed to disease development. According to County Agent Frank Winslow, the crop is anywhere from 8 to 28 days from harvest so the disease is early enough to impact yields.
Late blight occurs in North Carolina about once in every two or three years, but it generally occurs late enough that it does not impact yields. On rare occasions (approximately every 10 to 15 years) the disease will occur early enough to cause severe losses. This year’s outbreak is early enough to cause some concern, but its impact on yield will depend largely on future weather conditions and management practices.
The best way to control late blight is with preventive applications of effective fungicides. It is a difficult disease to control once it is established in the field. If the affected area is relatively small, disease spread can be minimized by killing diseased plants with an herbicide (e.g., Gramoxone). The area treated with herbicide should be large enough to include plants that are likely to be infected, but not yet showing symptoms. Fields in the immediate vicinity (1 to 3 miles) should be treated with an effective fungicide that can provide some systemic and curative activity. Other potato acreage in the area should at least begin a preventive program with chlorothalonil or mancozeb on a 5- to 7-day interval.
There are many fungicides with good to excellent activity against late blight. A listing of these products and their efficacy is available at: http://www.umaine.edu/umext/potatoprogram/Pest%20Control%20Guide/Fungicides.pdf.
From: Stephen B. Bambara, Extension Entomologist
Well, maybe it is not prevention, but now (and the for the next few weeks) is the time to scout and treat for bagworms, especially on evergreens. Agents will receive calls on this in mid to late summer. Treating bagworm host foliage with insecticide while they are small is the most effective time for control. Hand-picking bagworms, when practical, is a safe and effective means of control. Bagworms are still small enough to be barely noticeable and still eating small bites. Several insecticides are available if needed. See Ornamentals and Turf Insect Information Note Number 81 (http://www.ces.ncsu.edu/depts/ent/notes/O&T/trees/ort081e/ort081e.htm) for more information on bagworms.
Start examining cannas as the leaf whorls enlarge and begin to unfurl. Early larvae may appear, like leaf miners. This pest is more prominently recognized in the fall as the second generation damage becomes more noticeable and that's when agents are more likely to receive calls.
Lesser canna leafrollers are small caterpillars related to European corn borers, pickleworms, coneworms and sod webworms. Lesser canna leafrollers overwinter as larvae in the leaves and stems of canna and the moths emerge to mate and lay eggs after the new growth emerges in the spring. When the larvae hatch, they feed within the new, rolled leaves. Older larvae can actually tie the edges of older leaves together and roll the leaf! One mistake canna growers make is to leave the old dead growth on the canna bed as mulch. Canna seems to be the only host plant for this pest. If the plants are isolated from other cannas, it may be possible to drastically reduce the lesser canna leafrollers by carefully removing all dead leaves and stems in the fall after the frost has killed it back. It is possible to eliminate this pest by spraying Orthene several times at 10-day intervals. Bacillus thuringiensis (B.t.) insecticides are also effective for this pest. Landscapers are encouraged to spray the dilute pesticide mixture directly down into the rolled leaves so that the pesticide can soak into the shelter around the caterpillars. They are especially encouraged to gather and destroy all of the dead tops this winter after frost. For more information on lesser canna leafrollers, visit the following web site: http://ipm.ncsu.edu/AG136/cater12.html.
As usual, spruce spider mite and southern red mite damage are now being reported. And as mentioned in an earlier issue of the North Carolina Pest News, it is too late to treat for these cool season mites by the time symptoms appear. This on-again-off-again spring weather made it difficult to know when these mites were active in many areas of the state. For more information on spruce spider mites, see Ornamentals and Turf Insect Information Note Number 77 (http://www.ces.ncsu.edu/depts/ent/notes/O&T/trees/ort077e/ort077e.htm).
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Last modified on May 29, 2006 by Stephen J. Toth, Jr.
