File 2496 (15).qxd Bangladesh J. Sci. Ind. Res. 41(3-4), 239-244, 2006 Introduction The flour beetle Tribolium castaneum Herbst is one of the most destructive pests of stored food grains. It is generally found in granaries, mills, warehouses, etc. feeding on rice, wheat, flour, suji (a coarse flour of wheat), barley, etc. It is one of the major pests of stored products. The mentioned food items are significantly damaged by this pest in stor- age condition throughout the world. Because of the great economic importance of the pest, many studies on this beetle have dealt with its control. Mention may be made of the works of Pinniger, Strong and Tyler et al.1-3 Laboratory studies on the use of malathion as a grain protectant include those of Floyd, Lemon, Hosni et al., Strong et al., Lindgren et al., Gore, Watters, O’Donnell and Husain.4-12 All of them used malathion on adult Tribolium. Malathion gained wide acceptance and approval for use as protectant for stored grain. It has properties with emphasis on its low mammalian toxicity Parkin.13 Very little published works were available regarding the control of T. castaneum larvae with malathion (com- mercial grade) in the environment of Bangladesh. There is no published data on the control of Tribolium castaneum by com- mercial grade malathion in this country. This led to the present work. Synergistic effect of piperonylbutoxide on malathion is also incor- porated here. Materials and Methods The experimental insects were collected from the laboratory cultures and placed in petridishes containing treated whole meal flour. All the cultures were kept at a room temperature 20O ± 2O C. Experiments were carried out with 1st, 2nd and 3rd instar Efficacy of Malathion in Controlling Tribolium Castaneum Herbst (Coleoptera: Tenebrionidae) M. M. Husain and M. R. Hasan BCSIR Laboratories, Binodpur Bazar, Rajshahi, Bangladesh Abstract Effect of malathion on treated food medium was studied on adult and 1st, 2nd and 3rd instar larvae of Tribolium castaneum. The LD50 for the instars was 228.22, 78.13 and 183.01 ppm, respectively. The rate of mortality increased with increasing concentra- tions. Toxicity probably depended on the ingestion of the treated food medium. larvae. Combined effect of piperonylbutox- ide and malathion on adult was also incorpo- rated. Twenty larvae for each treatment were introduced in each petridish containing treat- ed food media. Each treatment consisted of 5 replicates. A similar treatment with untreated flour was also maintained. Standard concen- trations were prepared by adding 2 ml of malathion with 1000 ml of water to prepare 2000 ppm. The lowest concentrations were prepared by mixing water (1:1) with higher concentrations. Mortality counts of the instar larvae and adults were assessed after 20 days. The percentage mortality data were subjected to statistical analysis Busvine14 and the dose mortality relationship was expressed as a median lethal dose (LD50). For adults the effectiveness of the insecti- cides was evaluated by confining 50 test insects on wheat flour which had been treat- ed with insecticide and determining subse- quent knockdown and mortality. To deter- mine synergistic effects of piperonylbutoxide on adult T. castaneum required quantities of malathion alone and in combination with piperonylbutoxide was individually weighed using an electronic balance and mixed with wheat flour. After thorough mixing, the treated flour (approximately 1g) was then transferred to individual glass vials contain- ing Tribolium castaneum adults and secured at the top with cotton wool. Five doses of the insecticides were applied on the insects. Then mortality of the beetle was recorded LD50 and co-toxicity coefficients were calculated. The intensity of synergism was determined by co- toxicity coefficient which is measured by the ratios of the LD50 values of the toxicant done to the LD50 values of the toxicant in mixtures with the synergist x 100. If the co-toxicity coefficient is above 100, then synergism occurs.15 Results and Discussion The results of the dose mortality tests and statistical analysis are shown in Tables I and II and in Fig. 1. Malathion at 50 ppm was unable to give complete kill after 20 days from treatment. The dosage of 200 ppm cause 60, 80 and 56 % mortalities with 1st, 2nd and 3rd instar larvae of Tribolium casta- neum respectively within 20 days. The dosage of 160 ppm gave 23, 70 and 39 % mortalities with the 1st, 2nd and 3rd instar larvae respectively. Similarly, the dosage of 80 ppm gave 12, 60 and 29 % mortalities with larvae of the mentioned instars. It is observed that the mortality percentage increased with increase of dosage and duration. The present result is nearly similar to those of the previous workers (Pinniger, Hosni et al.)1,6 and Tyler et al.3 According to Tyler and Binns,3 the minimum dosage required to kill T. castaneum under low temperature condi- tions (5O C to 1O C) is 1395 mg/m2 of malathion. According to Hosni et al.,6 the LD50 for T. castaneum was 2.25 ppm. The present findings revealed that the LD50 for 1st, 2nd and 3rd instar larvae of T. castaneum was 228.224, 78.134 and 183.019 ppm 240 Efficacy of Malathion in Controlling 41(3-4) 2006 Husain and Hasan 241 Table I. Dose mortality response of the 1st, 2nd and 3rd instar larvae of T. castaneum exposed to different concentrations of Malathion. 1st 200 100 60 2.559 + 2.109x 228.224 425.014 122.552 160 100 23 80 100 12 40 100 8 20 100 2 control 100 0 2nd 200 100 80 1.131 + 2.043x 78.134 87.690 68.060 160 100 70 80 100 60 40 100 25 20 100 10 control 100 0 3rd 200 100 56 0.815 + 1.849x 183.019 225.367 148.635 160 100 39 80 100 29 40 100 11 20 100 3 control 100 0 Table II. Combined effect of malathion and piperonylbutoxide on Tribolium castaneum Herbst. Co-toxicity coefficient LD50 Percentage mortality Malathion Combined Malathion ppm Combined ppm Doses of insecticide of synergist (ppm) Malathion + piper- onylbutoxide 1:1 ratio Doses of insecticide (ppm) Malathion 200 400 60 74 160 320 44 54 80 160 34 41 138.25 251.74 109.84 40 80 15 21 20 40 5 9 Larval instar Concentration (ppm.) No of insect used Corrected % kill Regression equation Y LD50 (ppm) 95 % Confidence limit Upper (ppm) Lower (ppm) 242 Efficacy of Malathion in Controlling 41(3-4) 2006 Figure 1 (1st instar) 0 10 20 30 40 50 60 70 1 2 3 4 5 Mortality (%) D os es ( pp m ) Figure 2 (2nd instar) 0 10 20 30 40 50 60 70 80 90 1 2 3 4 5 Mortality (%) D os es ( pp m ) Fig. 1,2 & 3. Mortality response of the 1st, 2nd and 3rd instar larvae of T. castaneum exposed to different concentrations of Malathion. respectively. This difference was probably due to the difference in the emulsifiable concentrate formulations. Besides, Hosni et al.6 used adult for the experiments. Husain12 used premium grade malathion. It is, thus, inferred that malathion may be used in controlling this pest under pest man- agement programme. To assure best protec- tion against the pest, the highest dose should be applied. It appeared from the results (Table II) that malathion in combination with the synergist produced synergism to the adults of T. casta- neum. The results were discussed in relation to the potential use of piperonylbutoxide alone and in combination with malathion as synertgist in the control of adult Tribolium population. Acknowledgement The author thanks Professor Dr. K. A. M. S. H Mondal, University of Rajshahi, for supervising the experiments. M. M. Husain also wishes to thank Dr. M. O. Faruq (Ex- Director), BCSIR Laboratories, Rajshahi for his suggestions in preparing the manuscript. References 1. D. B. Pinniger. The behaviour of insects in the presence of insecticides : The effect of Fenitrothion nad Malathion on resistant and Susceptible strains of Tribolium confusum H. Proc. Ist. Int. Mg. conf. stored Prod. Ent., (1975) 301-308. 2. R. G. Strong. Relative susceptibility of Confused and Red flour beetles to twelve Husain and Hasan 243 Figure 3 (3rd instar) 0 10 20 30 40 50 60 1 2 3 4 5 D os es (p pm ) organophosphorus insecticides with notes on adequacy of the test method. J. Econ. Ent., 63(1) (1970) 258-263. 3. P. S. Tyler and T. J. Binns. The toxicity of seven organophosphorus insecticides and lindane to eighteen species of stored product beetles. J. Stored Prod. Res., 13 (1977) 39-43. 4. E. H. Floyd. Effectiveness of malathion dust as grain protectant for farm-stored corn in Louisiana. J. Econ. Ent., 54 (1961) 900-904. 5. R. W. Lemon. Laboratory evaluation of Malathion, Bromophos and Fenitrothion for use against beetles infesting stored products. J. Stored Prod. Res., 2 (1967) 197-210. 6. S. M. Hosni, A. K. M. Fahmy, EL-Nahat and E. Z. Fam. The effectiveness of five toxicants against three species of stored grain insects. Bull. Ent. Soc. Egypt, Econ. Ser., 3 (1969) 85-95. 7. R. G. Storng and D. E Sbur. Influence of grain moisture and storage temperature on the effectiveness of malathion as grain protectants. J. Econ. Ent., 53 (1960) 341- 369. 8. D. L. Lindgren, H. E. Krohne and L. E. Vincent. Malathion and chlorthion for control of insects infesting stored grain. J. Econ. Ent., 47(4) (1954) 705-706. 9. K. S. Gore. Laboratory experiments with some organic phosphorus insecticides as wheat protectants. Ph. D. Thesis, Cornel Univ. (Univ. Microfilms, Inc.) (1958). 10. F. L. Watters. Effects of grain moisture content on residual toxicity and repellency of malathion. J. Econ. Ent., 52 (1959) 131-134. 11. O’Donnell. The toxicities of four insecti- cides to Tribolium confusum Duv. in two sets of conditions of temperature and Humidity. J. Stored Prod. Res., 16 (1980) 71-74. 12. M. M. Husain. Dose mortality response of Tribolium confusum larvae to malathion, Bangladesh J. Sci. Ind. Res., 32(4) (1997) 599-601. 13. E. A. Parkin. A provisional assessment of malathion for stored product insect control. J. Sci. Food Agr., 6 (1958) 370-375. 14. J. R. Busvine. A critical review of the techniques for testing insecticides. Commonwealth Agricultural Bureaux, London (1977) 345. 15. Y. P Sun and F. R Johnson. Synergistic and antagonistic action of insecticide-synergist combinations and their mode of action. J. Agric. Food Chem. 8 (1960) 261-266. 16. M. M. Husain. Synergistic effect of piper- onylbutoxide on malathion to control adult Tribolium confusum Duval, Bangladesh J. Sci. Ind. Res., 31(4) (1996) 111-115. 244 Efficacy of Malathion in Controlling 41(3-4) 2006 Ahmed, Haque, Hossain, Rahman, Alamgir and Jalal 7 8 Study of Thermal Conductivity of Hexamethylene 41(3-4) 2006 Effect Of Plant Extracts on the Yield of Soybean 9 10 Effect Of Plant Extracts on the Yield of Soybean 41(1-2) 2006