Sunn
hemp, Crotalaria juncea,for Nematode Management
K.-H. Wang and R.
McSorley
Department
of Entomology and Nematology, University of Florida
Last update September 29, 2003
Mechanisms
of C. juncea suppressing plant-parasitic nematodes
How to enhance C. juncea
effects
|
|
b |
a
a
Fig. 1. a) Crotalaria
juncea at early flowering stage, b) C. juncea at vegetative stage.
Crotalaria
juncea L. is a rapid growing crop that is used for
fiber production in Indo-Pakistan. It is also good for use as a green manure in
many tropical and subtropical areas in the world as an organic and nitrogen
source. It suppresses weeds, slows soil erosion, and reduces root-knot nematode
populations (Rotar and Joy, 1983). When plowed under at early bloom stage,
nitrogen recovery is the highest. ‘Tropic Sun’ sunn hemp can produce 150 to 165
kg/ha of nitrogen and 7 t/ha air-dry organic matter at 60 days of growth under
favorable conditions (Rotar and Joy, 1983). In southwestern Alabama, plants
grown for 9 to 12 weeks produced 5.9 t/ha dry-matter and 126 kg N/ha (Reeves et
al., 1996). Leaving these residues on the soil surface over the winter
resulted in the release of 75 to 80 kg N/ha (Reeves et al., 1996). In
the tropics, ‘Tropic Sun’ grows and produces seed year round at elevation of 0
to 300 m, and in summer up to 600 m. In Guam and Puerto Rico, C. juncea
is grown under conditions similar to Hawaii. In the continental United States, C.
juncea is adapted to spring and summer planting in the South and Southwest
(Rotar and Joy, 1983) and can be grown as a winter cover crop in Alabama (Reeves et al., 1996). It is suitable as a green manure crop as far north
as Maryland, but may not seed well north of 30°
latitude. The biggest challenge of using C. juncea as cover crop in
U.S. is the seed availability (see
section below). Detail cultivation and other ecological information on C.
juncea can be obtained from http://www.hort.purdue.edu/newcrop/duke_energy/Crotalaria_juncea.html.
In
1958, the National Resources Conservation Service (NRCS) (formerly the Soil Conservation
Service), and the University of Hawaii purchased seeds of Crotalaria
from a farmer who was growing it as a cover crop on the island of Kauai. This
germplasm was used to develop C. juncea ‘Tropic Sun’. ‘Tropic Sun’ was released
in 1982 as a green manure crop by the NRCS and University of Hawaii (Rotar and
Joy, 1983). The Agricultural Research Service’s Poisonous Plant Laboratory and
the University of Hawaii determined that seeds of this cultivar were not toxic
to livestock, and the plant was resistant to root-knot nematodes (Rotar and Joy, 1983).
Suppression
of plant-parasitic nematodes by Crotalaria spp. has been known for
decades. Godfrey (1928) noted that C. juncea had few root galls from
infection with Meloidogyne spp. Most of the plant-parasitic nematodes
suppressed by Crotalaria are sedentary endoparasitic nematodes. These
include Meloidogyne spp. (Good
et al., 1965; McSorley et
al., 1994a; Taylor,
1985), Heterodera glycines (Rodríguez-Kábana et al., 1992) and Rotylenchulus reniformis (Robinson et al., 1997; Araya
and Caswell-Chen, 1994). Some migratory nematodes such as Belonolaimus
longicaudatus (Reddy et al., 1986), Paratrichodorous minor, Xiphinema
americanum (Brodie et al., 1970; Good et al., 1965), and Radopholus
similis (Birchfield and Bistline, 1956) were also suppressed by other
plants in the genus Crotalaria (Wang et al., 2002a). Crotalaria
juncea had been used as a preplant cover crop, intercrop, and for soil
amendment. Table 1 summarizes results of studies on host status of C. juncea
and effects of using C. juncea as a preplant cover crop or intercrop on
various plant-parasitic nematodes.
Table 1. Host status and
effects of using Crotalaria juncea in crop rotation or intercropping
system on plant-parasitic nematodes (From Wang et al., 2002b).
|
Nematode |
Host status |
Crop rotation or
intercropping effect |
|
Meloidogyne arenaria |
Poor host (McSorley, 1999) |
- |
|
M. exigua |
Resistant (Silva et al.,
1990a) |
- |
|
M. hapla |
Roots almost totally
galled, but few egg masses found (Martin, 1958). |
- |
|
M. incognita
race 1 |
Poor host (McSorley, 1999) |
Suppressed numbers on
cotton (Robinson et al., 1997). |
|
M. incognita
race 3 |
Resistant (Santos and
Ruano, 1987) |
- |
|
M. javanica |
Poor host (McSorley, 1999);
smaller giant cells (Silva et al., 1990b); no galls, no juveniles (Araya
and Caswell-Chen, 1994); galls visible (Martin, 1958). |
Suppressed numbers on taro
(Sipes and Arakaki, 1997); on tobacco (Shepherd and Barker, 1993); on
sugarcane (Moura, 1991). |
|
Pratylenchus brachyurus |
Survived but failed to
multiply (Charchar and Huang, 1981) |
- |
|
P. zeae |
Poorer host than sorghum
but can penetrate roots (Silva et al., 1989). |
- |
|
Rotylenchulus reniformis |
Poor host (Caswell et al.,
1991; Wang et al., 2001; Silva et al., 1989) |
Reduced numbers on pineapple
(Wang et al., 2002). |
|
Radopholus similis |
Leaf extract at 1:5
dilution is toxic (Jasy and Koshy, 1994); |
Intercropping with banana
reduced nematode numbers (Charles, 1995); did not suppress the nematodes when
grown as preplant cover crop without biomass incorporation (Inomoto, 1994). |
|
Helicotylenchus
multicinctus |
- |
Intercropping with banana
reduced nematode numbers (Charles, 1995). |
|
Hoplolaimus indicus |
- |
Intercropping with banana reduced
nematode numbers (Charles, 1995). |
Mechanisms of C. juncea suppressing
plant-parasitic nematodes
The
crop has few pest and pathogen problems. Major diseases of C. juncea are
Fusarium wilt caused by Fusarium udum var. crotalariae and
anthracnose caused by Collectotrichum curvatum (Purseglove, 1974). In Brazil, the only disease reported on the crop is
Ceratocystes fimbriata (National Research Council, 1979). The
three most serious insect pests for C. juncea are larvae of the sunn
hemp moth, Utetheisa pulchella, the stem borer, Laspeyresia
pseudonectis, and pod borers (Purseglove,
1974). Pod borers
can lower seed production of C. juncea. Crotalaria juncea
is also a host to stink bug, Nezara viridula (Davis, 1964) and African
sorghum head bug, Eurystylus oldi (Malden
and Ratnadass, 1998).
Shortage
of seed supplies and increased in seed prices is a draw back on cover cropping
of sunn hemp in U.S. Retail market value of seeds currently averages $4.00 /
kg. Recommended seeding rate for cover cropping is 40-65 kg / ha. This seed
cost is discouraging to growers (U.S. Department Agronomy, 1983). Attempt to
expand seed production of C. juncea in the U.S. beyond Hawaii is
challenging. It is known that C. juncea may not seed well north of 30° latitude. Climate in Florida should be
suitable for C. juncea seed production. However, in northern Florida, C.
juncea flowers well but seed production is poor (McSorley, personal
observation). In southern Florida, Abdul-Baki et al. (2001) proposed to
enhance C. juncea seed productions by increasing stem branching through
pruning at 90 cm.
How to enhance C. juncea effects
Although C. juncea has good
potential as a cover crop for managing several important plant-parasitic
nematodes, the residual effects are short term (a few months). While Crotalaria
juncea is a poor host to many plant-parasitic nematodes, nematode numbers
can resurge on subsequent host crops. The damage threshold level, especially on
longer-term crops, may be reached or exceeded (McSorley et al., 1994b).
This scenario strongly suggests that integrating the C. juncea rotation
system with other nematode management strategies is necessary. Among the
possibilities for integration are crop resistance, enhanced crop tolerance,
selection for fast growing crop varieties, soil solarization, and biological
control.
Nematicides should be avoided in a cropping
system if the objective is to enhance nematode-antagonistic microorganisms in
the cropping system. Several studies have demonstrated the destructive effect
of fumigation treatments to nematode antagonistic microorganisms (Kerry et al., 1995; Westphal
and Becker, 1999). Crotalaria juncea could enhance activities
of nematode-trapping fungi (NTF) in the rhizosphere or in soil amended with its
biomass (Wang et al, 2002,
2003), but it failed to enhance NTF populations in soils
that were recently treated with 1,3-dichloropropane (Wang et al, 2003).
However, development of microbial populations to a density needed to control
nematodes has occurred only under perennial crops or those grown in
monocultures (Kerry, 1987). Prolonged culture of Crotalaria in an
intercropping system enhanced the nematode suppressive effect in both peach (McBeth and Taylor, 1944) and pineapple systems (Wang et al, 2003).
Another approach worth exploring is the
search for biocontrol agents compatible with Crotalaria cropping
systems. Introduction of biocontrol agents to manage plant-parasitic nematodes
have met with limited success in the field (Stirling,
1991). The rhizosphere of legumes overcomes fungistasis
against the nematode-trapping fungi better than that of root-free soil (Persmark and Nordbring-Hertz, 1997). Although several attempts have failed to enhance
some nematophagous fungi by C. juncea (Venette
et al., 1997), in situ nematode-antagonistic microorganisms
associated with C. juncea rhizosphere and amended soils have not been
studied in depth. Such research studies might improve the prospect of
prolonging the nematode suppressive effect of C. juncea cropping
systems.
In summary, Crotalaria, besides
serving as an efficient green manure, is a poor host to many important
plant-parasitic nematodes, produces allelopathic compound toxics to nematodes,
and is able to enhance some nematode-antagonisitc microorganisms. Therefore
using C. juncea as a cover crop could offer alternatives to nematicides.
By integrating with other pest management strategies, development of new
sustainable agricultural cropping systems with C. juncea is promising.
ARAYA, M., and E. P. CASWELL-CHEN. 1994.
Host status of Crotalaria juncea, Sesamum indicum, Dolichos
lablab, and Elymus glaucus to Meloidogyne javanica. Journal
of Nematology 26: 492-497.
BIRCHFIELD, W., and F. BISTLINE. 1956.
Cover crop in relation to the burrowing nematode, Radopholus similis.
Plant Disease Reporter 40: 398-399.
BRODIE, B. B., J. M. GOOD, and C. A.
JAWORSKI. 1970. Population dynamics of plant nematodes in cultivated soil:
effect of summer cover crops in old agricultural land. Journal of Nematology 2:
147-148.
CASWELL, E. P., J. DEFRANK, W. J. APT, and
C.-S. TANG. 1991. Influence of nonhost plants on population decline of Rotylenchulus
reniformis. Journal of Nematology 23: 91-98.
CHARCHAR, J. M., and C. S. HUANG. 1981.
Host range of Pratylencus brachyurus: 3. Different species.
Fitopathologia Brasileira 6: 469-474.
CHARLES, J. S. K. 1995. Effect of
intercropping antagonistic crops against nematodes in banana. Annals of Plant
Protection Sciences 3: 185-187.
DAVIS, C. J. 1964. The introduction,
propagation, liberation, and establishment of parasites to control Nezara
viridula variety smaragdula (Fabricius) in Hawaii (Heteroptera:
Pentatomidae). Proceeding of Hawaiian Entomological Society 18: 369-375.
GODFREY, G. H. 1928. Legumes as rotation
and trap crops for pineapple fields. Experiment Station of the Association of
Hawaiian Pineapple Canners Bulletin 10: 3-21.
GOOD, J. M., N. A. MINTON, and C. A.
JAWORSKI. 1965. Relative susceptibility of selected cover crops and Coastal
Bermudagrass to plant nematodes. Phytopathology 55: 1026-1030.
INOMOTO, M. M. 1994. Host reaction of some
plant species to the burrowing nematode. Nematologia Brasileira 18: 21-27.
JASY, T., and P. K. KOSHY. 1994. Effect of
certain leaf extracts and leaves of Glyricidia maculata, (H. B. & K)
Steud. as green manure on Radopholus similis. Indian Journal of
Nematology 22: 117-121.
KERRY, B. R., D. H. CRUMP, and F. IRVING.
1995. Some aspects of biological control of cyst nematides. Biocontrol 1: 5-14.
KERRY, B. R. 1987. Biological control. in
R. H. Brown and B. R. Kerry, eds. Principles and practice of nematode control
in crops. Academic Press, Sydney.
MARTIN, G. C. 1958. Root-knot nematodes (Meloidogyne
spp.) in the Federation of Rhodesia and Nyasaland. Nematologica 3:332-349.
MALDEN, J. M., and A. RATNADASS. 1998. Crotalaria
juncea (Fabaceae) cited for the first time as alternative host of Eurystylus
oldi important pest of sorghum and ricinus (Hem., Miridae). Bulletin de la
Societe Entomologique de France 103: 272.
MCBETH, C. W., and A. L. TAYLOR. 1944.
Immune and resistant cover crops valuable in root-knot-infested peach orchards.
Proceedings of the American Society of Horticultural Sciences 45: 158-166.
MCSORLEY, R. 1999. Host suitability of
potential cover crops for root-knot nematodes. Supplement to the Journal of
Nematology 31: 619-623.
MCSORLEY, R., D. W. DICKSON, and J. A.
BRITO. 1994a. Host status of selected tropical rotation crops to four
populations of root-knot nematodes. Nematropica 24: 45-53.
MCSORLEY, R., D. W. DICKSON, J. A. BRITO,
T. E. HEWLETT, and J. J. FREDERICK. 1994b. Effects of tropical rotation crops
on Meloidogyne arenaria population densities and vegetable yields in
microplots. Journal of Nematology 26:
175-181.
MOURA, R. M. 1991. Two years of crop
rotation on sugarcane field to control root-knot part I; Effect of the
treatments on the nematode population. Nematologia Brasileira 15: 1-7.
NATIONAL RESEARCH COUNCIL. 1979. Tropical
legumes: resources for the future. National Academy of Science, Washington,
D.C. pp. 272-278.
PERSMARK, L., and B. NORDBRING-HERTZ. 1997.
Conidial trap formation of nematode-trapping fungi in soil and soil extracts. Federation
of European Microbiological Societies Microbiology Ecology 22: 313-323.
PURSEGLOVE, J. W. 1974. Tropical crops:
Dicotylendons. Longman Group Limited, London.
REDDY, K. C., A. R. SOFFES, G. M. PRINE,
and R. A. DUNN. 1986. Tropical legumes for green manure: II. Nematode
populations and their effects on succeeding crop yields. Agronomy Journal 78:
5-10.
REEVES, D. W., Z. MANSOER, and C. W. WOOD.
1996. Suitability of sunn hemp as an alternative legume cover crop. in
Proceedings of the New Technology and Conservation Tillage 96 (7): 125-130.
University of Tennessee Agricultural Experiment Station, Tennessee.
RICH, J. R., and G. S. RAHI. 1995.
Suppression of Meloidogyne javanica and M. incognita on
tomato with ground seed of castor, Crotalaria, hairy indigo and wheat.
Nematoropica 25: 159-164.
ROBINSON, A. F., R. N. INSERRA, E. P.
CASWELL-CHEN, N. VOVLAS, and A. TROCCOLI. 1997. Rotylenchulus species.
Identification, distribution, host ranges and crop plant resistance.
Nematropica 27: 127-180.
RODRÍGUEZ-KÁBANA, R., J. PINOCHET, D. G.
ROBERTSON, and L. W. WELLS. 1992. Crop rotation studies with velvetbean (Mucuna
deeringiana) for the management of Meloidogyne spp. Supplement to
Journal of Nematology 24: 662-668.
ROTAR, P. P., and R. J. JOY. 1983. 'Tropic
Sun' sunn hemp, Crotalaria juncea L. Research Extension Series 036.
College of Tropical Agriculture and Human Resources, University of Hawaii. 7
pp.
SANTOS, M. A. and O. RUANO. 1987. Reação de
plantas usadas como adubos verdes a Meloidogyne incognita raça 3 e M.
javanica. Nematologia Brasileira 11: 184-197.
SHEPHERD, J. A. and K. R. BARKER. 1993.
Nematode parasites of tobacco. Pp. 493-518 in M. Luc, R. A. Sikora and
J. Bridge eds. Plant Parasitic Nematodes in Subtropical and Tropical
Agriculture, 2nd ed. CAB International, Wallingford, UK.
SINGH, B. N., S. N. SIGHN, and M. B.
SRIVASTAVA. 1937. Photoperiodism, a factor in determining the manurial
efficiency and distribution of Crotalaria juncea. Journal of the
American Society of Agronomy 29:123-133.
SIPES, B. S., and A. S. ARAKAKI. 1997.
Root-knot nematode management in dryland taro with tropical cover crops.
Supplement to Journal of Nematology 29: 721-724.
SILVA, G. S., S. FERRAZ, and J. M. SANTOS.
1989. Resistência de espécies de Crotalaria a Pratylenchus brachyurus
e. P. zeae. 13: 81-86.
SILVA, G. S., S. FERRAZ, and J. M. SANTOS.
1990a. Effect of Crotalaria spp. on Meloidogyne javanica, Meloidogyne
incognita race 3 and Meloidogyne exigua. Fitopatologia Brasileira
15: 94-95.
SILVA, G. S., S. FERRAZ, and J. M. SANTOS.
1990b. Histopathology of Crotalaria roots infected with Meloidogyne
javanica. Fitopatologia Brasileira 15: 46-47.
STIRLING, G. R. 1991. Biological control of
plant parasitic nematodes. CAB International, Brisbane, Australia.
TAYLOR, S. G. 1985. Interactions between
six warm-season legumes and three species of root-knot nematodes. Journal of
Nematology 17: 367-370.
VENETTE, R. C., F. A. M. MONSTAFA, and H.
FERRIS. 1997. Trophic interactions between bacterial-feeding nematodes in plant
rhizospheres and the nematophagus fungus Hirsutella rhossiliensis to
suppress Heterodera schachtii. Plant and Soil 191: 213-223.
WANG, K.-H., SIPES, B.S., and SCHMITT, D.P.
2001. Suppression of Rotylenchulus
reniformis by Crotalaria juncea, Brassica napus, and Target erecta. Nematropica 31, 237-251.
WANG, K.-H., SIPES, B.S., and SCHMITT, D.P. 2002a. Management of Rotylenchulus
reniformis in pineapple, Ananas comosus, by intercycle cover crops.
J. Nematol. 34: 106-114.
WANG, K.-H., SIPES, B.S., and SCHMITT, D.P.
2002b. Crotalaria as a cover crop for nematode management: a review.
Nematropica 32:35-57.
WANG, K.-H., SIPES, and B.S., SCHMITT, D.P.
2003. Suppression of Rotylenchulus
reniformis enhanced by Crotalaria
juncea amendment in pineapple
field soil. Agriculture, Ecosystem and Environment 94: 197-203.
WESTPHAL, A., and J. O. BECKER. 1999.
Biological suppression and natural population decline of Heterodera
schachtii in a California field. Phytopathology 89: 434-440.