ALABAMA A&M AND AUBURN UNIVERSITIES

ANR-856 Suppressive Crops

lant parasitic are de- chrysanthemum, and castor bean, parasitic nematodes. In trials, Pstructive, hard-to-control soil partridge pea, several Crotalaria marigolds grown throughout the pests of vegetables, annual flowers, spp., velvetbean, sesame, and rape- summer suppressed common gar- woody ornamentals, and many row seed produce nematicidal (killing) den nematodes such as root-knot crops. Southern and peanut root- and nematistatic (suppressive) or- (Meloidogyne), lesion (Pratylen- knot nematodes are the two most ganic compounds. These natural chus), and stunt (Tylenchorhyn- common nematode pests. Control compounds, which are toxic to ne- chus) nematodes. Available evi- practices for these and other dam- matodes, are released from the dence indicates that all marigolds aging nematodes have largely fo- roots of living or by plants act generally as trap crops and also cused on yearly nematicide treat- incorporated into the soil as a contain chemicals toxic to nema- ments. However, nematicides for green manure. Some plants, which todes. home and farm use may not be also act as a trap crop, prevent ne- Not all marigold are ef- available in the future, so environ- matodes from maturing or repro- fective in suppressing populations mentally sound control practices ducing once they enter the roots. In of damaging nematodes. In fact, may have to be used to effectively addition, the roots of some of these some marigolds are susceptible to manage these damaging pests. plants simply may not be a good the less common ring (Cricone- One of these practices is grow- food source for nematodes, thereby mella), stubby-rot (Trichodorus), ing nematode suppressive crops. reducing their numbers by starva- and spiral (Rotylenchus) nema- Nematode suppressive crops pre- tion. Finally, the bacteria colonizing todes. vent the buildup of damaging lev- the roots of some plants may inter- Of all types of marigolds, els of nematodes naturally without fere with the life cycle of par- French dwarf marigolds ( nematicides or lengthy rotations to asitic nematodes. patula) give the most consistent non-host crops (see Table 1). control of the greatest number of Several plants may minimize Marigolds damaging nematodes species. nematode damage in the following The ever-popular marigold is (French dwarf marigolds known to vegetable and field crops. Some the most familiar of the plants suppress nematodes are listed in marigolds, a few varieties of known to actively suppress plant Table 2). Four other marigold

Table 1. Host Range Of Common Root-Knot Nematodes. Root-Knot Nematode Susceptible Resistant Southern cotton, soybean, corn, tobacco, peach, edible peanut, johnsongrass, strawberry, coastal beans, carrot, cucumber, cabbage, okra, potato bermudagrass, sorghum, millet (some), sweet potato, bahiagrass Peanut peanut, tobacco, soybean, corn, watermelon, sudangrass, cotton, coastal bermudagrass, carrot,ARCHIVE cucumber, eggplant, cabbage, pepper, sweet potato, sorghum (some), millet onion, potato, squash (some), bahiagrass Northern peanut, tobacco, soybean, cantelope, carrots, coastal bermudagrass, corn, cotton, okra, cucumber, eggplants, lima beans, onion, watermelon, bahiagrass pepper, lettuce, mustard, potato, snap bean, squash, sweet potato, tomato Javanese soybean, tobacco, corn, grain sorghum, peanut, cotton, pepper, strawberry, bahiagrass, vetch, clover, cowpea, cantelope, sweet potato, coastal bermudagrass, carrot, okra, beans, cabbage eggplant, marigold lettuce, onions, potato, squash, tomato

Visit our Web site at: www.aces.edu Table 2. Reaction Of Nematode Suppressive Crops To Common Nematode Pests. Common Root-knot Species Suppressive Crop Southern Peanut Northern Javanese French Marigold (Tagetes patula) ‘Tangerine’ ** ** ** — ‘Happy Days’ — — — ** ‘Lemondrop’ ** — — — ‘French Dwarf Double’ — — — — Chrysanthemum (C. morifolium) ‘Escapade’ ** — — — Castor Bean (Ricinus communis) ‘Bronze King’ ** — — — ‘Hale’ — ** — — Partridge Pea (Cassia fasciculata) —**— Showy Crotalaria (C. spectabilis) ** ** — ** Florida Velvetbean (Mucuna deeringiana) ** ** — ** Common Vetch (Vicia sativa) ‘Cahaba White’, ** ** — ** ‘Vantage’, ‘Nova II’, ‘Vanguard’, and ‘Warrior’ — ** — — Rapeseed (Brassica napus) ‘Juniter’, ‘Cascade’, ‘Elena’, ‘Indore’, ** — — ** ‘Humus’, ‘Bridger’, and ‘Dwarf Essex Sesame (Sesame indicum) —**—— **indicates a high level of suppression. —indicates no suppression or no available data. species, including some cultivars of nematode (P. alleni). Reaction of Tropical Legumes the African (T. erecta) and South cvs. ‘Lemondrop’ and ‘Happy Days’ American (T. minuta) marigold, re- to other root-knot nematode Tropical legumes are often duce numbers of root-knot nema- species is not known. In another used as summer annual forages for tode. study, the cv. ‘French Dwarf grazing livestock and for improving soil fertility. Some have been Control of root-knot nematode Double’ greatly reduced popula- shown to suppress damaging ne- with French dwarf marigolds is tions of reniform nematode. matodes. Foliage of some tropical complicated by the number of root- A few marigolds scattered legumes incorporated into the soil knot species found in Alabama through a vegetable garden will not as a green manure may also reduce soils. All French dwarf cultivars are control plant parasitic nematodes. populations of some root-knot ne- not equally effective in controlling For effective nematode suppression matodes. a mixed population of several root- with marigolds, solid seed the gar- knot nematode species. In one den with a recommended cultivar Many tropical legumes are study, the French dwarf marigold from Table 2. Maintain the solid highly susceptible to attack by all cv. ‘Tangerine’ suppressed repro- stand of marigolds for at least 2 common root-knot nematodes. duction on southern (M. incogni- months and then turn them under Carpon desmodium (Desmodium ta), northern (M. hapla), and with a plow or rototiller as green heterocarpon), hairy indigo (Indi- peanut (M. arenaria) root-knot ne- manure. Keep the treated area gofera hirsuta), pigeonpea (Caja- matodes while cvs. ‘Petite weed free until the next vegetable nus cajan), and alyceclover (Alysi- Harmony’, ‘Petite Gold’, and crop is planted. carpus vaginalis) should not be ‘Goldie’ supported some root-knot planted in areas infested with root- While marigolds can suppress knot nematode. reproduction. The cv. ‘PetiteARCHIVEnematodes, they can also cause Harmony’ was very susceptible to other problems. Dense stands of Forage crops that may be used several root-knot species. In anoth- marigolds are weeds in a vegetable for nematode suppression in veg- er study, the French dwarf cv. garden because they compete with etable gardens and row crop fields ‘Lemondrop’ controlled southern crops for essential nutrients and are discussed below. root-knot. When planted as a cover water. In many gardens and land- Castor Bean (Ricinus commu- crop before carrot, the French scape beds, marigolds are also a nis) greatly reduces survival of ju- dwarf cv. ‘Happy Days’ greatly re- common source of spider mites. veniles and reproduction of south- duced damage caused by javanese ern, peanut, and lesion nematodes. root-knot (M. javanica) and lesion Castor bean cultivars evaluated for

2 Alabama Cooperative Extension System nematode suppression are listed in manure, allowed to mature before industrial oil. Normally, this crop is Table 2. Castor beans should be the tops are chopped down with a planted in the fall and harvested for plowed under as a green manure disk, or cut as hay for cattle or seed in the spring. Rapeseed con- before a seed crop is set. A single other livestock. tains sulfur-containing chemicals seed contains enough poison to kill (glucosinolates) that break down in humans, pets, and livestock. Seed Temperate Legumes decomposing tissues into com- availability is limited. pounds toxic to nematodes. Temperate legumes are often American Jointvetch. When Rapeseed cultivars 'Dwarf Essex’, planted as a winter cover crop in incorporated as green manure, ‘Elena’, ‘Indore’, ‘Jupiter’, ‘Cascade’, gardens and row crop land. American jointvetch (Aeschyno- ‘Bridger’, and ‘Humus’ are effective Common vetch (Vicia saliva) and meme americana) suppresses the in suppressing southern and ja- hairy vetch (V. villosa) are widely peanut root-knot nematode. vanese root-knot nematodes. cultivated as winter cover crops. However, other trials have shown However, some rapeseed cultivars Caley pea (Lathyius hirsutus) has that American jointvetch is suscepti- support high populations of the also been used as a cover and for- ble to five root-knot species, in- southern root-knot nematode and age crop on calcareous clay soils in cluding southern and javanese root- reproduction of the less common Alabama and Mississippi. knot nematodes. Therefore, this northern root-knot nematode. forage legume should not be used Use of these cover crops for Rapeseed is most effective to suppress nematodes in a garden nematode suppression is discussed against nematodes when incorpo- or most row crop production sys- below. rated as a green manure 2 to 3 tems. Common Vetch. Cultivars of months after planting in the fall. Partridge Pea. Grown for 2 common vetch are resistant to the Mature rapeseed (6 months old) years, partridge pea (Cassia fascic- southern, peanut, and javanese plowed under as a green manure ulata) will reduce populations of root-knot nematodes. Those culti- has little affect on root-knot nema- peanut root-knot nematode. Since vars are 'Cahaba White’, ‘Vantage’, tode populations. Early the effect of partridge pea on the ‘Nova II’, and ‘Vangard’. The culti- (September) plantings of rapeseed more common southern root-knot var ‘Warrior’ is highly resistant to should be avoided. species is not known, partridge pea the peanut root-knot nematode. is not recommended as a nematode The broad resistance of the above Bahiagrass suppressive crop in home gardens common vetch cultivars makes Bahiagrass, a widely used but may be rotated with peanuts. them suitable for use as a winter warm-season perennial pasture- Also, partridge pea’s small, hard cover crop in gardens and some grass in the southern two-thirds of seed makes this forage a potential row crops. Common vetch may be Alabama, is an excellent nematode weed problem. a weed problem if allowed to set seed. suppressive crop of all important Showy Crotalaria (C. Hairy Vetch. Because hairy root-knot species. This aggressive spectabilis) is reported to be highly grass is especially well adapted to resistant to the southern, peanut, vetch is highly susceptible to sever- al root-knot species, this legume the well-drained soils of Alabama’s and javanese root-knot nematodes. coastal plain. Its resistance to a broad range of should not be grown on root-knot Bahiagrass rotations provide root-knot nematodes makes showy infested garden and croplands. excellent suppression of peanut crotalaria a suitable rotation and Caley Pea. In screening trials, and southern root-knot nematodes. green manure crop in home gar- caley pea has supported some re- Long-term bahiagrass rotations pro- dens. Showy crotalaria should be production of the peanut root-knot vide the additional benefit of sup- grown as a green manure because nematode. Reaction of this legume pressing soil-borne diseases (white its tops and seed are toxic to live- to the southern and javanese root- mold and vascular wilts) and im- stock and humans. knot nematodes is unknown. proving soil tilth. All bahiagrass va- Velvetbean. If velvetbean Because little information is avail- able concerning the reaction of rieties are easily established from (Mucuna deeringiana)ARCHIVEis grown seed. the year before planting peanuts, caley pea to several damaging ne- In most fields and gardens, root exudates of velvetbean and as- matodes, it is not recommended as bahiagrass works best when grown sociated rhizobacteria reduce popu- a cover crop on nematode infested for a minimum of three summers. lations of the peanut root-knot ne- sites. Often, two summer crops can be matode. Velvetbean also reduces grown with little interference from juvenile populations of the south- Rapeseed nematodes or soil diseases before ern and javanese root-knot nema- Rapeseed (Brassica napus) is reseeding bahiagrass. When grown tode. Velvetbean may be incorpo- an annual winter crop grown for rated into the soil as a green

Nematode Suppressive Crops 3 for at least 4 years, bahiagrass pas- suppress nematode populations Effects of rapeseed and vetch as ture controls nematodes and soil- sufficiently to eliminate the need green manure crops and fallow on borne diseases in root-knot sensi- for a nematicide treatment on the nematodes and soil-borne patho- tive field and vegetable crops. following year’s peanut crop. gens. Journal of Nematology Shorter bahiagrass rotations will 24:117-126. greatly reduce juvenile numbers Conclusion Mojtahedi, H., G. S. Santo, A. but some damage, particularly in N. Hang, and J. H. Wilson. 1991. Growing a nematode suppres- fields or gardens with exceptionally Suppression of root-knot nematode sive crop will not eliminate plant high root-knot populations, will populations with selected rapeseed parasitic nematodes from the soil. occur. In those fields or gardens cultivars as green manure. Journal However, it may reduce nematode with high larval populations, bahia- of Nematology 23:170-174. numbers enough to allow produc- grass should be grown for a mini- Rodriguez-Kabana, R., and G. mum of 5 years before the field is tion of nematode susceptible plants in a nematode infested field, bed, H. Canullo. 1992. Cropping systems rotated back to a nematode suscep- for the management of phytonema- tible crop. or garden. If nematode populations are high, cropping several succes- todes. Phytoparasitica 20(3):211- When tall fescue or coastal sive suppressive or non-host crops 224. bermudagrass is used in place of will be needed before a susceptible Rodriguez-Kabana, R., N. bahiagrass, the same cropping pat- crop may be grown without the Kokalis-Burelle, D.G. Robertson, terns should be followed. If protection of a nematicide. Nema- L.W. Wells. 1994. Evaluation of broadleaf weeds in a bahiagrass tode populations often can re- Sesame for Control of Melotdogynl pasture are not controlled, some bound to pretreatment levels on a arenaria and Scleratium rolfsil in nematode damage may be seen. susceptible vegetable or field crop peanut. Nematropica 24:55-61. grown after the production of a ne- Rodriguez-Kabana, R., J. Sesame matode suppressive crop. Pinochet, D. G. Robertson, and L. Sesame (Sesame indica), a crop Nevertheless, suppression of nema- Wells. 1992. Crop rotation studies valued for its oil and seed, has sup- todes by growing nematode sup- with velvetbean (Mucuna deeringi- pressive activity against the peanut pressive crops has been similar to ana) for the management of root-knot nematode. When grown or somewhat better than suppres- Meloidogyne spp. Annals of Applied as a summer annual, this crop has sion of nematodes obtained with a Nematology (Journal of Nematology proven equally if not more effective weed-free summer fallow. 24, Supplement) 24(4S):662-668. than bahiagrass and cotton in re- Rodriguez-Kabana, R., D. G. ducing the carryover of peanut Some Additional Robertson, L. Wells, P S. King, and root-knot nematode juveniles in the Sources Of Information C. E Weaver. 1989. Crops uncom- soil in a peanut or soybean produc- mon to Alabama for the manage- tion system. The status of sesame Bernard, E. C., and M. E. ment of Meloidogyne arenaria in as a host of other species of root- Montgomery-Dee. 1993. peanut. Annals of Applied Nema- knot nematode commonly found in Reproduction of plant-parasitic ne- tology (Journal of Nematology 20, Alabama has not been determined. matodes on winter rapeseed Supplement) 20(4S):712-715. Sesame may be rotated with (Brassica napus spp. oleifera). Taylor, S. G., D. D. peanut, soybean, and possibly cot- Annals of Applied Nematology Baltensperger, and R. A. Dunn. ton. A single crop of sesame in a (Journal of Nematology 25, 1985. Interactions between six field heavily infested with the Supplement) 25(4S):863-868. warm-season legumes and three peanut root-knot nematode will not Johnson, A. W., A. M. Golden, species of root-knot nematodes. D. L. Auld, and D. R. Sumner. 1992. Journal of Nematology 17:367-370.

ARCHIVEAustin Hagan, Extension Plant Pathologist, Professor; William Gazaway, Extension Plant Pathologist, Professor; and Ed Sikora, Extension Plant Pathologist, Associate Professor; all in Plant Pathology at Auburn University

For more information, call your county Extension office. Look in your telephone directory under your county’s name to find the number.

Issued in furtherance of Cooperative Extension work in agriculture and home economics, Acts of May 8 and June 30, 1914, and other related acts, in cooperation with the U.S. Department of Agriculture. The Alabama Cooperative Extension System (Alabama A&M University and Auburn University) offers educational programs, materials, and equal opportunity employment to all people without regard to race, color, national origin, religion, ANR-856 sex, age, veteran status, or disability. 5M, Reprinted Sept 1998, ANR-856