 |
Field and Forage Crops |
We are starting to see a lot of worms in peanuts. It appears to be quite a mixture in many areas with corn earworms being the predominant species. That is a mixed blessing in that while corn earworms are typically a little bit easier to kill, they also cause quite a bit of damage. That is why the threshold is 4 worms per row foot in August. Vine growth is quite extensive in many areas and I think the plant can certainly tolerate quite a bit of feeding. We are also anticipating quite a bit of rain over the next few days from the tropical storms and hurricanes. Heavy rains have been one of the best worm control products I have seen in peanuts. Be sure and recheck peanuts next week after the rains before treating. Remember that fall armyworms are not as damaging and I usually say we should double the threshold for treating. However, they are usually mixed with corn earworms and they are harder to kill. Check control recommendations. There are a few beet armyworms in fields and the product Steward is effective against beet armyworms and products like Lannate and Tracer will do OK against smaller ones. IF the rains come through as predicted, I think many of our worms problems will subside in peanuts.
Wet weather in many portions of the state has led to a proliferation of foliar and other diseases. Thus far, there have been numerous confirmed cases of frogeye leaf spot on soybean. This is a destructive disease of soybean that can be prevented by the uses of resistant varieties. Soybean varieties range from highly resistant to very susceptible. In 2003 many soybean fields were prematurely defoliated by this disease. Based on fungicide trials, yield losses of 30% have been reported as a result of this disease. Symptoms are spots on leaves that have a distinctive reddish to brownish border. Spots are typically less than 5mm in diameter, although spots may coalesce to form larger often irregular lesions. The leaf spots can be confused with soybean downey mildew, which is also quite common this year. Additional fungal foliar diseases that have been observed include brown spot and anthracnose. More information about these diseases and aids in identification can be found on the web at http://cipm.ncsu.edu/ent/SSDW/soyatlas.htm and http://www.ces.ncsu.edu/depts/pp/notes/Soybean/soybean_contents.html Fungicide sprays may be warranted for frogeye leaf spot, especially for highly susceptible varieties planted after small grains. The decision to spray full season soybean is more difficult, since in many instances yield potential may not be adequate to justify an economic return, or disease may have progressed too far to control. The fungicides TopsinM, Quadris, and Bravo are labeled for use on soybean. Follow label directions if a decision to spray is made. Fungicides will not control bacterial blight.
Saturated soils in many locations in North Carolina have resulted in an increase in the amount of soybean root and stem rots. Phytophthora root and stem rot, Southern blight, Sudden Death Syndrome (SDS), and red crown rot (also called black root rot), are quite common this year. Intervienal chlorosis and (or) necrosis is generally indicative of SDS or red crown rot, although occasionally Phytopthora root rot or Southern blight will cause similar foliar symptoms. Both SDS and red crown rot cause a reddish to brownish discoloration of the vascular tissue that usually extends only an inch or two above the soil line. The pith will usually remain white. SDS is generally more severe in no-till and varieties vary in susceptibility. Susceptibility of varieties to red crown rot is not known. Phytophthora root rot can generally be distinguished from SDS and red crown rot by examining split stems. Dark or rotted pith, often with pith disking that may extend several inches to more than a foot through the stem is characteristic of Phytopthora root and stem rot. Southern blight typically runs down the row, and often white fungal strands covered with brown to black sclerotia about the size of a mustard seed are visible on the stem. Foliar applications of fungicides will have no impact on these diseases. More information on these diseases is available at http://cipm.ncsu.edu/ent/SSDW/soyatlas.htm and http://www.ces.ncsu.edu/depts/pp/notes/Soybean/soybean_contents.html
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 August 30, 2004 by Stephen J. Toth, Jr.