Vegetable Virus Problems in South Florida As Related to Weed Science
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168 FLORIDA STATE HORTICULTURAL SOCIETY, 1971 18. Sylvester, E. S. 1955. Lettuce mosaic virus trans 20. Zink, F. W., R. G. Grogan, and J. E. Welch. 1956. mission by the green peach aphid. Phytopathology 45:357-370. The effect of the percentage of seed transmission upon sub 19. Weber, G. F. and A. C. Foster. 1928. Diseases of sequent spread of lettuce mosaic virus. Phytopathology lettuce, romaine, escarole and endive. Florida Agr. Exp. 46:662-664. Sta. Bull. 195: 30 pp. VEGETABLE VIRUS PROBLEMS IN SOUTH FLORIDA AS RELATED TO WEED SCIENCE J. R. Orsenigo and T. A. Zitter Both crop and weed plants may serve as reser voirs for the maintenance and/or propagation of IF AS Agricultural Research and Education Center plant viruses. Viral infestations of plants can be Belle Glade mitigated through eradication of cultivated and wild host reservoirs, control of virus vectors, and Abstract use of healthy or resistant propagules. Previous Most plant viruses require living plant ma work in Florida has pointed-up the importance of terial for survival and propagation. Some viruses eradication of wild host reservoirs in the control may infect a wide range of crop and weed plants of virus diseases of celery, pepper, tomato, and while others are highly specific in their host cucurbits (1, 9, 11, 12, 13). Theoretically, the relationships. Plant viral infections can be miti simultaneous eradication of crops, weeds, and gated by eradication of cultivated and wild host their propagules from a specific area should elimi reservoirs, control of virus vectors, and use of nate viral infections. healthy or resistant propagules. The more import ant viruses in the south Florida area are: bidens Major Virus Diseases mottle, lettuce mosaic, potato Y, southern celery The most important virus diseases of vegetable mosaic, tobacco etch, tobacco mosaic, watermelon crops in south Florida are: bidens mottle (BMV), mosaic, and western celery mosaic. The principal lettuce mosaic (LMV), potato Y (PVY), southern crops affected by these viruses are: celery, cu celery mosaic (SCMV, or cucumber mosaic CMV), cumber, endive, escarole, lettuce, pepper, potato, tobacco etch (TEV), tobacco mosaic (TMV), summer squash, tomato, and watermelon. The more watermelon mosaic (WMV), and western celery important known hosts of these viruses include: mosaic (WCMV). hairy beggarticks, creeping cucumber, dayflower, groundcherry, black nightshade, and Virginia pepperweed. Control of these and other virus host Major Vegetarle Crops Affected plants is related to their habitats, seasonal cycles, The principal crops affected by viruses are: and herbicide susceptibilities. celery (Apium graveolens L. var. dulce Pers), Live vegetation is necessary for the mainten cucumber (Cucumis sativus L.), endive (Chicorium ance and reproduction of most plant viruses. Plant endivia L.), escarole (Chicorium endivia L.), lettuce viruses require active plant growth for multiplica (Lactuca sativa L.), pepper (Capsicum annuum tion, but some may survive in dormant plant pro L.), potato (Solanum tuberosum L.), summer pagules, seed, or vegetation. Plant viruses tend to squash (Cucurbita melopepo Alef.), tomato (Ly'co be host specific and do not infect wild or crop persicon esculentum Mill.), and watermelon (Cit- plants indiscriminately, but the host range of some rullus vulgaris Schrad.). viruses includes many botanical families, genera and species. Viral specificity could be based on Major Weed Hosts* virus-plant interactions including the ability of a virus to survive or multiply in a given plant, or Usual botanical style has been modified for the the transmitting agent. Virus particles must be following weed descriptions. transmitted physically or mechanically by animate or inanimate means. *Weed descriptions are adapted from: Miller, J. F., et al. 1969. Weeds of the southern United States. Cooperative Ex tension Service — Southern Region States; and, Small, John Florida Agricultural Experiment Stations Journal Series Kunkel. 1933. Manual of the southeastern flora. The Univer. No. 4203. sity of North Carolina Press, Chapel Hill, p. i-xxii, 1-1554, ORSENIGO AND ZITTER: VEGETABLE VIRUS AND WEEDS 169 Hairy beggarticks, Bidens pilosa L. Appears on slender stalks attached to branches between similar to spanishneedles, B. bipinnata L. but lacks the leaves. The fruit is a small, smooth black deeply cut leaves. Leaves opposite on stems and berry. An inhabitant of cultivated and abandoned branches. Flower heads borne singly on the ends crop land and non-crop areas. of long, largely leafless terminal branches. Flowers Virginia pepperweed, Lepidium virginicum L. have yellow centers and white ray petals. Seed Primarily a winter annual which may germinate, long, narrow, pointed, dark-brown to black in grow and flower sporadically throughout the year. color with 2 to 4 barbed spines. This is primarily Smooth, erect, branched stems may reach 2 feet an annual plant which may survive as a perennial in height. Long, narrow, smooth, slightly toothed in frost-free areas. Seed may germinate through leaves borne alternately. Long finger-like flower out the year in warm periods and plants may clusters (racemes) borne at stem and branch tips flower every month of the year where free of may be as long as the vegetative plant is tall. frost. Found mainly along fields, roads, ditchbanks, Small flowers develop into circular, flat, top-notched and fencerows and in non-cropped areas and is pods. Racemes frequently grow for extended peri rarely an important weed of crop fields in south ods and have mature seed below and buds above Florida. open flowers. A weed of cultivated and abandoned Creeping cucumber, Melothria pendula L. A land and especially roadsides, fencerows, and non- slender, climbing vine which may grow perennially crop areas. in warm, frost-free areas. Leaves smooth, ovate, and shallowly-lobed. Flowers bright yellow, female flower larger than male. Fruit a green to blackish Minor Weed Hosts ellipsoidal juicy berry V2 to 1 inch long. Climbs Balsamapple, Momordica charantia L. A slender, trees, brush, fences, abandoned buildings, trash creeping, climbing, branched frost-sensitive vine. piles and herbaceous plants as well as creeping Light-green, broad, deeply lobed (5 to 7), toothed over low-growing plants and the soil line. leaves may be nearly smooth or hairy on smooth Day flower, Commelina spp. A low-growing or hairy petioles. Yellow flowers about 1 inch frost-sensitive annual with semi-erect, spreading wide develop into softly-spined, irregular, ridged, or creeping, succulent, green to brownish stems. 2-inch golden berries which rupture open natur Alternate, short, lance-shaped leaves clasp the ally at the blossom end to reveal small, bright red stem. Irregular blue to violet flowers borne in keel- seed attached to the inner flesh of the fruit. Climbs shaped structures. A weed of moist fields, ditch- trees, brush, fences, abandoned buildings, trash banks, fencerows, and non-crop areas. piles, and herbaceous plants as well as low-grow Groundcherry, Physalis sp. Some species are ing plants and the soil line. annuals which grow perennially in frost-free loca Cressleaf groundsel, Senecio glabellus Poir. Pri tions; other species are perennial or resprout from marily a winter-spring annual which germinates underground rootstocks when aerial parts are massively in January-February following cold killed by frost. Smooth to hairy, purple or dark weather although occasional specimens may be splotched, erect, branching stems grow to three found growing and flowering in almost all months. feet tall. Oval, smooth, variously toothed 2-inch Coarsely-toothed leaves with large terminal lobes leaves borne alternately. Broad, bell-shaped, droop form a rosette. A green, erect, hollow stem up to ing flowers light to greenish yellow. The fruit is 2 feet tall may develop upper branches. Terminals a round, green berry completely enclosed by green of stems and branches bear bright yellow flowers or brown, papery bladder-like sepals. They are in clusters. An infestant of pastures, roadsides and inhabitants of cultivated and abandoned crop land uncultivated areas. and non-crop areas. Common lambsquarters, Chenopodium album L. Black nightshade, Solanum nigrum L. Occurs Primarily a cool to warm season annual germinat with and is difficult to distinguish from Solanum ing in late winter and spring through summer. graaile Link. It is an annual which may grow Stems and branches form an erect plant 1 to 6 perennially in frost-free locations. Smooth, erect, feet tall with vertical ridges and often with reddish branched stems may develop into globular or free- or pale green vertical striping. Branches profusely. form bushes to 3 feet tall. Oval to elliptic, smooth, Margins of alternate leaves are ragged toothed. lightly toothed leaves borne alternately. Small Undersides of leaves are greyish-green while young flowers, five white linear petals around a yellow leaves often have white, powdery "bloom" on upper center, borne in groups of small, hanging clusters surfaces. Small flowers borne densely on spikes 170 FLORIDA STATE HORTICULTURAL SOCIETY, 1971 from leaf axils and branch terminals. A weed of tices must destroy the entire host plant, including cultivated crops, road and field margins, and non- underground roots and stems capable of sprouting crop areas. and regenerating. Mockbishopweed, Ptilimnium capillaceum Crop and weed hosts mentioned herein are (Michx.) Raf. Primarily a fall-winter-spring an controllable with chlorophenoxy herbicides. Two nual requiring cool weather and moist soil condi specific chemicals of choice, 2,4-D and silvex, tions for massive germination and best growth. applied as foliar wetting sprays should be effective Plant arises from feathery, finely-branched basal in most circumstances for mixed plant populations. leaves. One or several, green to reddish-brown, Silvex alone at 1.5 lb/A is preferable if black vertically ridged, variously branching, erect stems nightshade and groundcherry occur uniquely. Cellu- range from 1 to 2 feet tall. When plant has many losic spray thickeners may be used to increase stems it may assume a bushy appearance. Leaves spray solution viscosity and minimize spray drift opposite, feathery, and relaxed.