LD SfpSS A '7~ I P4 & s.u. ~ . 2.1 LIBRAR1PLANT DISEASE CONTROL NOTES c. t- EXTENSION DIVISION e VIRGINIA POLYTECHNIC INSTITUTE AND STATE UNIVERSITY PMG 21 July 1978 BLACKSBURG, VIRG ~~ANUT STUNT VIRUS by Sue A. Tolin and Jane E. Polston* Peanut stunt virus (PSV) causes at the edges (Fig. 2). The leaves may be paler diseases of peanut, tobacco, clover, soybean, green and/or yellowed. The fruit of infected and snap-beans in Virginia. This relatively peanut plants is frequently small and new virus was first found in Virginia when, malformed, and the shells of the peanuts are in 1964, it caused severe losses in peanut. In split (Fig. 3). Yields are reduced because of a 1976, PSV caused substantial losses to decrease in the amount of fancy pods, extra garden and field beans. PSV has several large kernels, and sound mature kernels. wild plant hosts and is spread by aphids. SYMPTOMS The symptoms of peanut stunt virus vary with the crop, the variety of the crop, the strain of PSV, the age of the plant at the time of infection, and weather conditions during the growing season. In peanut, the whole plant (Fig.1), parts of the plant, or just branch tips will be severely stunted. Following very early infection, a plant may never grow beyond a few inches in height and width. The leaves of infected plants are malformed and curl up Figure 2. Figure 1. *Associate Professor and Graduate Assistant, respectively, Department of Plant Pathology and Physiology. Figure 3. l In tobacco, PSV causes whole leaves or parts of leaves to become a bright yellow, a symptom known as "white top". The whole plant or just upper leaves will be stunted also. The leaves of infected plants show a mosaic pattern of green and yellow areas. Garden and field beans become severely stunted when infected with PSV, and may fail to grow beyond two or three leaves. The leaves of infected plants are reduced in size, malformed and curled at the edges (Fig. 4). A mosaic pattern of green and yellow is also seen on the leaves. The pods of infected bean plants are smaller, twisted, malformed, and are "waxy" in appearance (Fig. 5). Figure 5. source of virus for the next year's crop since the virus remains in them throughout the winter. Infected peanut seed do not play a role in the disease cycle since only seed too small to plant are infected at a high enough rate to act as a source ofinfection. However, some bean seeds may contain PSV and produce infected plants. CONTROL Virus-infected plants cannot be cured, but virus infections can be minimized or prevented. The first step in control is an accurate diagnosis of the problem, since Figure 4. virus infections can resemble other diseases. There are few control measures for PSV. 1. DISEASE CYCLE The best control is to plant PSV­ reSistant varieties of crop plants. No PSV can be found in white clover and resistant cultivars of peanut, tobacco, crownvetch in Virginia. It survives the or soybean have been found to date. winter in these and other wild legumes 'Roma', 'Topcrop', and 'Tendercrop' (clovers, alfalfa, lespedeza, etc.). In the give better yields than do some other spring, as aphids feed on infected wild infected snap-bean varieties. 'Half­ legumes, they pick up PSV in their runner', 'Blue Lake', and wax beans mouthparts and spread the virus to the next are severely damaged. several plants they feed on. In this way, 2. A void planting susceptible crops aphids spread PSV to other wild legumes near fields of clover, mixed legumes, and to susceptible crop plants in the same and crownvetch. and nearby fields. Once inside the plant, the 3. Plant peanut seed certified to be free virus particles increase in number and from PSV by the Virginia spread to other parts of the plant. In the fall, Department of Agriculture and the wild legumes die back but will be the Commerce. 2 TECHNICAL DESCRIPTION Peanut stunt virus is a member of the Cucumovirus group and has microscopic spherical particles (Fig. 6). PSV is mainly spread by the aphids Myzus persicae (green peach aphid) and Aphis craccivora (cowpea aphid). Trifolium repens (white clover) and Coronilla varia (crownvetch) are the most important natural hosts of peanut stunt virus. Figure 6. DISEASE CYCLE OF PEANUT STUNT VIRUS PSV overwinters in wild legum~-- wil~. legume ...... ; • • -.• . : J,. .~ .. " •• ..... : •• • • •• '-;. SPRING WINTER \ 0 virus multiplies 0 0 0 0 0 0 virus multiplies 0 0 0 } SUMMER 0 0 Figure 7. 3 The Virginia Cooperative Extension Service by law and purpose is dedicated to serve all people on an equal and nondiscriminatory basis. An Equal Opportunity/ Affirmative Action Employer Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. W. R. Van Dresser, Dean, Extension Division, Cooperative Extension Service, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061. 4 .