Introduction Symptoms & Signs Causal Organism Chemical Control References
Variety selection is one of the most important decisions in disease management. The development and release of disease-resistant varieties of peanut continue to make a significant contribution to CBR management. In general, spanish varieties are most resistant to CBR and valencia varieties are highly susceptible to the disease. Virginia- and runner-type varieties range from moderately resistant to highly susceptible. Although CBR-resistant, virginia-type breeding lines have been described and released, only a few commercial varieties (NC 10C, NC 12C) offer a moderate level of resistance at this time. NC 9 has exhibited good tolerance to CBR and has been used successfully when seed of NC 10C or NC 12C were not available. NC 10C, NC 12C and NC 9 should be used with the metam sodium treatment in heavily infested fields. NC-V 11, and VA-C 92R are acceptable choices for planting with the metam sodium treatment in fields having moderate to light infestations of the disease. NC 6, NC 7 and VA 93B are highly susceptible to CBR and generally should be avoided. NC 9, NC 10C, NC 12C without a metam sodium treatment should perform well in fields with light infestations. Another factor to consider in variety selection is the presence of other pathogens in a field. NC 9 is highly susceptible to early leaf spot, and both NC 9 and NC 12C are highly susceptible to Sclerotinia blight.
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Leaf spot |
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Sclerotinia |
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Stem rot |
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Pod rot |
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CBR |
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Carefully planned crop rotations and cultural practices are important for disease management with a CBR-resistant cultivar. Because of cooler soil conditions and the probability of higher levels of soil moisture, peanuts planted early are more vulnerable to CBR damage than those planted late. Crop rotation with non-host crops such as corn, small grains, cotton or tobacco may help reduce the incidence of CBR, whereas rotations with leguminous crops such as soybean can result in increased populations of the CBR-fungus in soil. Rotational systems that use non-host crops for three or more years between peanut croppings help to reduce levels of soil inoculum in fields.
Tillage practices that maximize exposure of microsclerotia to winter temperatures may reduce levels of over-wintering inoculum significantly. Removal and destruction of peanut hay and no soil tillage until spring may also reduce inoculum survival. Movement of the pathogen from field to field can be minimized by cleaning field implements and combines to remove adhering soil and plant debris. Peanut seed harvested from fields with the disease have been shown to carry the fungus at low levels. Seed treatment fungicides and winter storage can drastically reduce levels of the fungus in seed, but generally do not eliminate the risk for disease spread through seed transmission. Peanuts harvested from fields with severe disease should not be saved for seed.
The severity of CBR increases when roots are parasitized by the northern root-knot nematode (Meloidogyne hapla) and the ring nematode (Criconemella ornata). Metam sodium treatment along with the application of Temik 15G at 5 to 7 lb/A in the seed furrow provides good control of these nematodes as well as CBR. The severity of CBR on peanut may be increased by root injury caused by certain pre-plant herbicides. Always use pre-plant, soil-incorporated herbicides at recommended rates. Some downward adjustment of rates may be necessary to avoid concentrating these herbicides in the row when fumigating and bedding soil for CBR control.
Introduction Symptoms & Signs Causal Organism Chemical Control References
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http://ipm-www.ento.vt.edu:8000/nipmn/VA-IPM/cblackrot/cultural.htm
Last Updated on March 5, 1998 by Barron Britt Keeling