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Comparative Efficacy of Candidate Termiticides Against Worker Termites, Odontotermes obesus (Rambur)
T.D. Kakde, P.M. Siddhabhatti, P.R. Panchbhai and
R.M. Wadaskar
140, Bhau Saheb Surve Nagar
Nagpur - 440 022 (MS), India.
(M): +91 9890 464949
College of Agriculture, Nagpur
Dr. Panjabrao Deshmukh Krishi Vidyapeeth,
Akola (Maharashtra), India.
ABSTRACT In Central and North India termites, Odontotermes Sp .is reckoned as a pest of economic importance for several economically important crops like Groundnut, Maize, Wheat, sugarcane and cotton inflicting damage up to 60 percent. Adverse effect of persistent organochlorine and Cyclodienes, primarily used for termite control on environment provoked the need to screen ecologically safer insecticides against termites, Odontotermes obesus (Rambur).
Application of Chlorpyriphos + Cypermethrin (Nurelle D) recorded the lowest median lethal concentration (0.0017%) and the highest relative toxicity of 2.29 as significant over application of Chlorpyriphos, 1.0,the standard check with LC50 value of 0.000395. Application of Cypermethrin + Chlorpyriphos and Cypermethrin alone proved superior over Chlorpyriphos in terms of the lowest median lethal time. For 50 percent mortality of assorted worker termites population.
KEY WORDS Odontotermes obesus, Termiticide
INTRODUCTION Subterranean termites are the major pest of agriculture and human structures throughout tropical and subtropical climatic zones causing damage worth billions of dollars worldwide. As per the pest ranking system (based on severity of damage inflicted) developed by Natural Resource Institute, United Kingdom,the termite was rated as rank one pest in wheat not only at Indian but also at the South Asian level. (Geddes and Iles, 1991). Odontotermes is identified as an important pest in Central and North India causing damage to the extent of 60 percent in several economically important crops like Groundnut, Maize, Wheat, Sugarcane and Cotton (Mishra, 1999).
Management of Subterranean termites primarily relies on treatment of soil at the site of active infestation. Offlate, increased environmental concern due to several unintended repercussions of persistent Organochlorines and Cyclodienes like Aldrin, Dieldrin, Chlordane and Heptachlor, though the most effective and long lasting insecticides for the control of termites has prompted the need for screening newer potent insecticides against termites (Khoo and Sherman, 1979).
Thus, the present study was framed with a view of screening five candidate termiticides belonging to different classes viz., Cypermethrin (Synthetic Pyrethroid), Chlorpyriphos (Organophosphate), Nurelle D (Chlorpyriphos + Cypermethrin, a Combination Product), Carbaryl (Carbamate) and Lindane (Organochlorine) for their efficacy against assorted population of worker termites, Odontotermes obesus.
MATERIALS AND METHODS Collection of termites, Odontotermes was done with the help of modified bucket trap as described by Su and Scheffrahn, 1986, after location of live termitoria in the fields from 4 villages of Nagpur district (Maharashtra). The assorted population of collected worker termites was maintained in the laboratory, Department of Plant Pathology, College of Agriculture, Nagpur on fungus comb (the natural food collected from termitoria). The culture was maintained at 25 ±2 șC with relative humidity of 80 - 90 percent. Due care was taken for acclimatization of worker termites before proceeding for the bioassay (Gurusubramanian et. al., 1999).
Five dilutions of each insecticide were prepared by serial dilution method in distilled water. Insecticides in powder formulations were diluted with talk powder. The bioassay was carried out in plastic cup (4.5cm x 6.5cm x 5.0cm) covered with a black cloth. A wet filter paper was placed at the bottom of each cup to maintain necessary humidity along with a layer of sterilized soil and fungus comb as a food source. A set of 12 worker termites replicated thrice was subjected to each concentration of five insecticides. The insecticide dilutions were applied to the worker population @ 2 ml/cup with the help of hand atomiser, whereas, the control set was sprayed with same quantity of distill water to record any natural mortality in worker population. Dilutions of insecticides in powder form were applied @ 2 gm/cup on the soil surface with workers and the control set was given the same quantity of talk powder to record any natural mortality.
Treated as well as termites in control set were maintained at 25 ±2 șC temperature and 80-90 percent Relative Humidity. The mortality count was recorded every 24 hours for 7 days after application of treatment. The moribund workers (unable to produce coordinated movement of body when prodded) were considered as dead. Bioassay data was pooled and concentration mortality and time mortality regression was computed by POLO - PC software for Probit analysis (Anonymous, 1987). Relative toxicity of insecticides under consideration was calculated by dividing LC50 due to Chlorpyriphos by LC50 of the insecticide to ascertain the potency of candidate termiticides over Chlorpyriphos, the standard check.
RESULTS AND DISCUSSION For nearly five decades, management of Subterranean termites have extensively relied on treatment of soil with persistent insecticides. Though, Chlorpyriphos became available in the 1980`s, people mostly employed the use of persistent Organochlorines and Cyclodienes as a termite management strategy until the ban was imposed on these insecticides. As a consequence of the adverse effects of these chemicals on environment, research focus was shifted towards screening of new, less harmful candidate termiticides with long residual activity that is highly repellent or inflicting rapid kill like Organophosphtes and Pyrethroids (Su and Scheffrahn, 1992).
Concentration mortality regression analysis (Table 1) indicates the superiority of Nurelle - D (Chlorpyriphos + Cypermethrin ) in terms of lowest median lethal concentration, 0.0017 percent against the assorted population of worker termites followed by Chlorpyriphos (0.0039 %), the standard check. These treatments were superior when compared with other insecticide treatments like Cypermethrin (0.0155 %), Carbaryl (0.0327 %) and Lindane (0.1183 %), respectively. There were significant toxicity differences between Chlorpyriphos + Cypermethrin (Nurelle D) and Chlorpyriphos also between Chlorpyriphos and Cypermethrin determined by non overlap of 95 percent Fiducial Limits at LC50 values of these insecticides.
Higher efficacy of Chlorpyriphos against the termite's population was reported by Khoo and Sherman, 1979, Su et. al.,1982, Su and Scheffrahn,1990 and 1992, Goyal,1994 along with Mishra,1999 whereas, higher potency of Cypermethrin (Su and Scheffrahn, 1990) and lower efficacy of Carbaryl (Smith,1979 and Su et. al.,1982) and Lindane was reported by Arora and Arora,1995 which are in corroboration with the present findings. Estimation of relative toxicity values (Table 1) is indicative of the fact that the combination product, Nurelle D was 2.29 times effective over Chlorpyriphos, whereas, rest of the insecticides (Cypermethrin - 0.25, Carbaryl - 0.12 and Lindane - 0.03) were not comparable with efficacy of the Chlorpyriphos (1.0), the standard check.
Time mortality response data (Table 2) of insecticide dilutions constituting LT50 and LT90 (range) reflects the higher potency of Nurelle D in terms of lower time (0.4 days for 0.05 %, 0.6 days for 0.005 % and 1.3 days for 0.0005 %, respectively) to record 50 percent mortality in worker termites. The former treatment was followed by Cypermethrin (LT50 values, 0.5 days for 1.0 %, 0.9 days for 0.1% and 1.5 days for 0.01% concentration, respectively) superior over the standard check, Chlorpyriphos which registered LT50 values of 0.8 days for 0.2 percent, 1.2 days for 0.02 percent and 2.4 days 0.002 percent concentration respectively, strongly supported by the findings of Su and Scheffrahn, 1990.
Rest of the treatments viz., application of Carbaryl and Lindane followed the low efficacy trend as in case of concentration mortality response. On the contrary application of Nurelle D and Cypermethrin shows promise to be used as termiticides besides Chlorpyriphos, the standard check.
REFERENCES
Anonymous (1987) : POLO - PC a users guide to probit or logit analysis. 22 pp. California, Le Ora Software, California.
Arora, K. and Arora, S.S.(1995) : Lindane as termiticide. A review. In terrmite Management in Buildings. (Ed. Y. Singh) pp. 56 - 59. Tata Mcgraw Hill Publishing Company Limited, New Delhi.
Geddes, A. M. W. and Iles, M.(1991) : The relative importance of crop pests in South Asia. Nat. Resour. Inst. Bull. No. 39, Natural Resource Institute, Chatham, Maritime, Kent, UK.
Goyal, D. D. (1994) : Antitermite treatment in buildings. Construc. Rep. 1 : 5 - 8.
Gurusubramanian, G., Tamuli, A. K. and Ghosh, K. R.(1999) : Susceptibility of Odontotermes obesus (Rambur) to Beauveria bassiana (Bals.) Vuill. Insect Sci. Application. 19(123) : 157 - 162.
Khoo, B. K. and Sherman, M.(1979) : Toxicity of Chlorpyriphos to normal and defaunated Formosan Subterranean termites. J. Econ. Entomol. 72 : 298 - 304.
Mishra, H. P.(1999) : Efficacy of Chlorpyriphos against termites in groundnut. Indian J. Ent. 61(4) : 326 - 329.
Smith, V. K. (1979) : Improved techniques designed for screening candidate termiticides on soil in the Laboratory. J.Econ. Entomol. 72 : 877- 879.
Su, N. Y., Tamashiro, M., Yates, J. R. and Haverly, M.I.(1982) : Effect of behavior on the evaluation of insecticides for prevention of or remedial control of the Formosan Subterranean termites. J. Econ. Entomol. 75 : 188 - 193.
Su, N. Y. and Scheffrahn, R. H. (1986) : A method to access, trap and monitor field populations of the Formosan Subterranean termites (Isoptera : Rhinotermitidae) in the urban environment . Sociobiology 12(2) : 299 - 304.
Su, N. Y. and Scheffrahn, R. H.(1990) : Comparision of eleven soil termiticides against the Formosan Subterranean termites and eastern Subterranean termites (Isoptera : Rhinotermitidae). J. Econ. Entomol. 83 (5) :1918 - 1924.
Su, N. Y. and Scheffrahn, R. H.(1992) : Longevity and efficacy of Pyrethroid and Organophosphate termiticides in field application using miniature slabs. J. Econ. Entomol. 92 (4) :898 - 904.
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