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Bhardwaj, H.L., A.A. Hamama, D.M. Porter, and P.F. Reese, Jr. 1996. Rapeseed meal as a natural pesticide. p. 615-619. In: J. Janick (ed.), Progress in new crops. ASHS Press, Arlington, VA.

Rapeseed Meal as a Natural Pesticide*

Harbans L. Bhardwaj, Anwar A. Hamama, D. Morris Porter, and Paul F. Reese, Jr.

  1. METHODOLOGY
  2. PESTICIDAL EVALUATION
  3. GERMPLASM EVALUATIONS
  4. REFERENCES
  5. Table 1
  6. Table 2
  7. Table 3
The current interest in glucosinolates and the associated degradation products stems from the possibility of using them as pesticides. Glucosinolates are organic anions possessing a ß-D-thioglucose moeity (Brown et al. 1991) decomposing to form isothiocyanates, the same class of chemical compounds produced by the decomposition of metam-sodium (Vapam).

Cruciferous plant tissues or tissue extracts, which contain high amounts of glucosinolates, have been reported to be phytotoxic (Jimenez-Osornio and Gliessman 1987; Fenwick et al. 1983) and insecticidal (Lichtenstein et al. 1964). The most thoroughly described control of a plant pathogen is for Aphanomyces root rot of peas, in which a variety of cruciferous plant amendments applied to infested soil reduced either the level of Aphanomyces euteiches (f. sp. pisi W.F. Pfender & D.J. Hagedorn) or the severity of the disease symptoms (Papavizas 1966; Papavizas and Lewis 1971; Lewis and Papavizas 1971, Chan and Close 1987). Glucosinolates from rapeseed (Brassica napus L.) meal were shown to have anti-fungal activity against Cylindrocladium parasiticum (Crous, Wingefield and Alfenas), casual agent of Cylindrocladium black rot (CBR) of peanuts, by Adamsen et al. (1991).

Considerable demand exists in the United States for industrial feedstocks and products from high erucic acid oil. Existence of glucosinolates restricts the use of protein-rich, defatted meal, from industrial rapeseed, as livestock feed. Development of defatted rapeseed meal as a natural annually-renewable biocide can not only help the environment but also has the potential to support industrial base of U.S. industry by providing a boost to development of rapeseed as a domestic source of high erucic acid oil.

The main objective of these studies was to ascertain efficacy of glucosinolate-rich rapeseed meal to control CBR in peanut and SCN (soybean cyst nematode, Heterodera glycines Ichinohe) in soybean. Our intent in conducting these experiments was not to develop rapeseed as a new crop to provide meal for use as a natural pesticide but to find a use of the meal so that production of industrial rapeseed as an oilseed can be facilitated. Accessions of Brassica napus and B. rapa were evaluated for winter hardiness in a separate study.

METHODOLOGY

CBR and SCN incidence was determined in replicated field experiments following three rates of soil-treatment with rapeseed meal (1, 2, or 3 t/ha), a commercial pesticide (Vapam for peanut and Aldicarb for soybean), and an untreated control. Both Vapam and Aldicarb were applied at rates recommended in the production area. The rapeseed meal was obtained from the Department of Agricultural Engineering, University of Idaho.

Two peanut cultivars, 'NC6' (susceptible) and 'NC10C' (resistant), were used for CBR studies. Six soybean lines/cultivars (susceptible/tolerant, G88-20092 and 'Hutcheson'; susceptible/intolerant, 'Essex' and 'Toano'; and resistant 'Asgrow 5403' and 'Deltapine 415') were used for SCN studies. The layout of field experiments was a split-plot design with soil-treatments in main-plots and cultivars in sub-plots. Each sub-plot consisted of four rows with 1 m and 0.45 m spacing between rows, respectively for peanuts and soybean. The rapeseed meal and Vapam treatments were applied to peanut experiments with a tractor-driven spreader/sprayer. In the soybean experiments, rapeseed meal was spread manually in each main-plot. The rapeseed meal in soybean experiments was spread on May 2, soybean were planted on May 23, and Aldicarb was applied on May 27, 1994. Rapeseed meal was spread in peanut experiments on May 2 and peanuts were planted on May 16, 1994. The peanut sub-plots were 15 m long whereas soybean plots were 6 m long. A constant length was harvested from two middle rows of each plot at maturity. The peanut plots were scored for CBR incidence in Sept., 1994 with a disease severity index of 1 (all plants healthy in 15m row) to 10 (all plants in a 15m row length exhibiting typical CBR symptoms). Each row of each sub-plot was scored and averaged for CBR incidence.

Soil samples were taken on May 2, June 29, Oct. 7, 1994 in soybean experiments. These samples were kept under refrigeration until determination of SCN cysts and larvae by Department of Plant Pathology, Virginia Tech, Blacksburg.

PESTICIDAL EVALUATION

The rapeseed meal was effective as a pesticide to control CBR of peanut. The rapeseed meal reduced the disease incidence by 7%, 25%, and 70% over control in `NC6', a susceptible cultivar, when 1, 2, or 3 t/ha, respectively of rapeseed meal was used as soil treatment. The lowest disease incidence on `NC6' occurred with Vapam (Table 1). However, a clear reduction in disease incidence was observed with increasing rate of rapeseed meal. Similar results were also obtained from 'NC10C', a resistant cultivar. All three rapeseed meal treatments resulted in significantly lower disease incidence as compared to control. However, the lowest incidence still occurred when Vapam was used, indicating that resistance alone may not be adequate to control CBR incidence in peanut. The yield of 'NC6', following soil treatment with 3 t/ha of rapeseed meal, was similar to that following treatment with Vapam and the yield following soil treatment with 1 or 2 t/ha was significantly higher than that from the control treatment. In the case of 'NC10C', Vapam treatment resulted in significantly higher yield as compared to the other four treatments. The yield differences among rapeseed meal treatments and control were not significant.

The results with soybean were unclear. The number of cysts was significantly lower when 2 t/ha rapeseed meal was used with resistant cultivars but increased with susceptible-tolerant ones (Table 2). The larval population of soybean cyst nematodes, generally, increased over time when 2 or 3 t/ha of rapeseed meal was used. The seed yields (Table 3) of soybean cultivars were similar following five soil treatments.

GERMPLASM EVALUATIONS

In a separate experiment, 938 accessions of Brassica napus and B. rapa, supplied by USDA-ARS, Plant Introduction Station, Ames, Iowa, were evaluated in single row observation plots during 1993-94 for winter hardiness at Petersburg, Virginia. Five hundred accessions from this collection were identified to be cold-tolerant. The glucosinolate content in seeds of these accessions, when determined using TRUBLUGLU meter (Truscott et al. 1991), varied from 38 to 77 µmol/g. The glucosinolate content in 456 napus accessions as a group was 49 µmol/g which was significantly greater than the mean glucosinolate content of 44 µmol/g in 44 rapa accessions. The oil content was determined in 159 accessions. The 122 napus accessions (38.4%) had significantly higher oil content than that of 37 rapa accessions (36.5%). A significant positive correlation (0.63** for napus and 0.79** for rapa accessions) existed between oil content and glucosinolate content.

The results from one year's field studies indicate that rapeseed meal has pesticidal properties against Cylindrocladium parasiticum, casual agent of Cylindrocladium black rot (CBR) of peanuts. Further evaluations are needed to confirm these results and to determine if rapeseed meal has potential to control soybean cyst nematode.

REFERENCES

*This material is based upon work supported by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Cooperative Agreement No. 93-COOP-1-9523. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the view of the U.S. Department of Agriculture.
Table 1. Cylindrocladium black rot (CBR) disease scores on peanut cultivars at Suffolk, Virginia following rapeseed meal and other soil treatments during 1994.

CBR severity scoresz Yield (kg/ha)
Soil treatment NC10Cx NC6y NC10C NC6
Untreated 4.9aw 8.9a 3612b 2643c
Vapam 1.2c 1.8c 4364a 4359a
Meal (1 t/ha) 3.4b 8.3a 3594b 3221b
(2 t/ha) 2.6b 6.7b 3897b 3194b
(3 t/ha) 2.7b 2.7b 3959b 4027a
zDisease index from 1 (all plants healthy) to 10 (all plants exhibiting typical CBR symptoms).
yResistant to CBR.
xSusceptible to CBR.
wMean separation in columns by Duncan's Multiple Range Test (5% level).

Table 2. Soybean cyst nematode populations following soil treatments with rapeseed meal or Aldicarb during 1994.

Sample datez
Treatment Cultivar T1 T2 T3
No. cysts
Meal (1 t/ha) Resistant 63 33 56
Susceptible-Intolerant 63 41 45
Susceptible-Tolerant 63 48 88
(2 t/ha) Resistant 71ay 62ab 31b
Susceptible-Intolerant 71 85 51
Susceptible-Tolerant 71 61 69
(3 t/ha) Resistant 92 73 61
Susceptible-Intolerant 92 64 67
Susceptible-Tolerant 92 60 78
Aldicarb Resistant 41 45 35
Susceptible-Intolerant 41 45 65
Susceptible-Tolerant 41b 37b 102a
Untreated Resistant 50 45 42
Susceptible-Intolerant 50 64 55
Susceptible-Tolerant 50 66 75
No. larvae
Meal (1 t/ha) Resistant 170 70 227
Susceptible-Intolerant 170 88 178
Susceptible-Tolerant 170 110 260
(2 t/ha) Resistant 133 205 137
Susceptible-Intolerant 133 87 165
Susceptible-Tolerant 133b 102b 450a
(3 t/ha) Resistant 43b 133a 150a
Susceptible-Intolerant 43 155 153
Susceptible-Tolerant 43b 88b 282a
Aldicarb Resistant 110 162 103
Susceptible-Intolerant 110 122 193
Susceptible-Tolerant 110 197 258
Untreated Resistant 63 97 110
Susceptible-Intolerant 63 62 106
Susceptible-Tolerant 63b 148ab 297a
zT1 = Sampled before planting, May 2, 1994
 T2 = Sampled after planting, June 29, 1994
 T3 = Sampled before harvest, Oct. 7, 1994
yMean separation between T1, T2, or T3 within treatments and cultivars by Duncan's Multiple Range Test (5% level)

Table 3. Seed yield of soybean cultivars following soil treatments with rapeseed meal or Aldicarb during 1994.

Seed yield (kg/ha)
Soil treatment Resistantz Susceptible/
intolerant		 Susceptible/
tolerant
Untreated 2368y 1336y 1800y
Aldicarb 2688 1566 1997
Meal (1 t/ha) 2700 1510 2103
(2 t/ha) 2401 1179 2004
(3 t/ha) 2488 1046 1972
zClassification of soybean cultivars based on reaction to infestation by soybean cyst nematode.
yNo significant differences within columns (Duncan's Multiple Range Test, 5% level).

Last update July 1, 1997 aw