l.Biol.Control, 8 (1), 14-17, 1994 Relative Toxicity of Certain Insecticides to Adelencyrtus mayurai (Subba Rao), A Parasitoid of Sugarcane Scale Insect, Melanaspis glomerata (Green) s. EASWARAMOORTHY, H. DAVID and K. SUBADRA BAI Division of Crop Protection Sugarcane Breeding Institute, Coimbatore - 641 007 ABSTRACT Toxicity of seven insecticides viz. •carbosnlfan, dimethoate, malathion, monocrotophos, cypermethrin, decamethrin and fenvalerate each at three concentrations were tested for their relative toxicity to Adelencyrtus mayurai (Subba Rao), the principal parasitoid of sugarcane scale insect, Melanaspis glomerata (Green),by exposing the adults to the treated surface. At recom­ mended concentration, both fenvalerate (31.3 % mortality) and deltamethrin (49.9%) proved to be less toxic to the adult parasitoids. Malathion caused 93.0% mortality, while the other insecticides inflicted cent per cent mortality. The mortality increased with increase in the concentation of the insecticides and decreased with increase in time lag between treatment with insecticide and exposure of the parasitoid to the treated surface. KEY WORDS: Adelencyrtus mayurai, parasitoid, Melanaspis glome rata, insecticide susceptibility Adelencyrtus mayurai (Subba Rao) (Encyr­ (Nuvacron 36 WSC), cypermethrin (Ripcord 10 tidae:Hymenoptera) is an important and widely EC) and decamethrin (Decis 2.8 EC) were' distributed uniparental parasitoid of sugarcane selected based on their efficacy in the"'control scale insect, Melanaspis glomerata (Green) of ·;the scale insect (Muralikrishna', 1984). (Venkateswara Rao, 1983; Easwaramoorthy Three concentrations of each insecticide, a andKurup, 1986; Easwaramoorthy etal., 1983, r~commended dose, half the recommended 1986). Under field ccinditio)1s, theaV"crage .,:dose and one and half times the recommended level of parasitization observed was 8.68 per" ,\~dose (Table 1) were tested. Cane pieces of 15 cen't (Venkateswara Rao and David,1986j\At:~ '<em, colonised with sparse population of scale tempts made on mass. multiplicatio~·andfield insect (Easwaramoorthy and Shanmugasun­ colonisation against M. glomerata has given daram, 1991) were sprayed with the insecticide promising results (Anon., 1989). To combat solution. After shade-drying, the lower cut end scale insect menace, chemical control measures of the cane piece was planted in a tray contain­ combined with detrashing is currently recom­ ing sand. Filter paper cut to the size of the base mended. It is essential to know the safety of the of the chimney was kept surrounding the cane insecticides recommended for the control of sett. Top end of the chimney was covered with scale insect to the principal parasitoid so as to a muslin cloth held in position by a rubber integrate various control methods. In the band. present study, the relative contact toxicity of sc yen insecticides as foliar sprays to A. Twenty five freshly-emerged parasitoids' mayurai was determined. were released into each chimney, containing the insecti~ide-treated cane setts with host in­ MATERIALS AND METHODS sects. Setts dipped in water served as control. The treatments were replicated four times. Cot­ Seven insecticides viz., carbosulfan (Mar­ ton swab dipped in 50% honey placed on the shal 24 EC), dimethoate (Rogor 30 EC), inner side of the chimney served as food for the, malathion (Malamar 50 EC), monocrotophos Toxicity of insecticides to A. mayurai 15 parasitoids. After confinement of the respectively. Cypermethrin, carbosulfan and parasitoids inside the chimney for one hour, monocrotophos caused 100% mortality at all they were transferred to fresh chimnies con­ the three doses tested. Between the different taining untreated cane setts colonised with doses tested, low dose of the .insecticide (half scale insects. Mortality was recorded after 24 the. recommended dose) was found to be sig­ hours. nificantly less tox~c (65.8%) followed by recommended dose (71.9%). Dosage above the In the second experiment, the cane setts recommended concentration was highly toxic were treated with recommended dose of the and it caused 83.6% mortality. insecticides. The cane setts were exposed to the parasitoids 1, 24, 48 and 72 hours after treat~ Cent per cent mortality was observed even ment. The experiment was conducted as when the parasitoids were exposed 72 h '~fier detailed under the first experiment. treatment in monocrotophos, carbosulfanand cypermethrin (Table 2). Dimethoate and Mortality data were converted into arc sine malathion retained fairly high degree of x ...Jpercentage after converting zero values to toxicity even at 72 h. Though cypermethrinwas 0.1 and analysed using 'F' test. more toxic compared to decamethrin initially, at 48 and 72 h after treatment it showed sig­ RESUL TS AND DISCUSSION nificantly less mortality. At the normal recommended dose, sig­ nificantly low mortality (31.3%) of the From the study it can be inferred that syn­ parasitoid was recorded in decamethrin treat­ thetic pyrethroids like fenvalerate . and ment. This was followed by fenvalerate decamethrin were relati vely safer to A. mayurai (49.9%). Malathion recorded a significantly than the other insecticides tested. Synthetic higher mortality of 93.0%. Dimethoate, car­ pyrethroids were reported to be less harmful to . bosulfan, monocrotophos and cypermethrin several other parasitoids (Waddil,1978; Wilkinson 1979; Mani and Krishnatnoor­ caused 100% mortality of the parasitojq~ et ai., (Table 1). thy, 1984; Varma et al., 1988) and a dipteran parasitoid Stu rm iopsis , inferens Tns (Eas­ When all the three concentration~ were' waramoorthy et at.. 1990).' However, cyp<et­ considered together, significantly less JUOT" methrin was found to behighly toxic to the tality (48.8%) was observed in fenvalerate fol~ parasitoid. The insecticides, malathion and lowed by decamethrin (53.0%). Malathion 'lno dimethoate which are currently recommended dimethoate recorded 89.6 and 98.4%morta.lity for scale insect control were found to be more Table 1. Effect of different concentrations of inse~ticides on the mortality of A. mayurai , Concentration tested (!fa) Adult mortality* atconcentration (%) Insecticide Recom- Recom- Pooled Low High Low High mended mended mean c c b c Malathion 0.05 0.1 0.15 78.0 93.0 97.6 89.6 Dimethoate .0.04 0.08 0.12 95.3d 100.Od 100.Od 98.4d a b a Fenvalerate 0.005 0.01 0.015 23.7 49.9 73.0 '48.9a Cypermethrin 0.01 0.02 0.03 100.Oe 100.Od 100.0d 100.Oe Ciubosulfan 0.01 0.02 0.03 100.Oe 100.Od 100.Od 100.Oe Monocrotophos 0.1 0.2 0.3 100.Oe 100.Od 100.Od 100.Oe b a c b Decamethrin 0.01 0.02 0.03 29.7 31.3 98.3 53.0 Mean 65.8 71.9 83.6 * Means followed bythesame letters are not different statistically (P=O.05) by LSD 16 EASWARAMOORTHY et al. Table 2. Per cent mortality of A.mayurai adults exposed to insecticides at different intervals after treatment Adult mortality (%) h post treatment* Treatment 1 24 48 72 Mean c c c Malathion 0.1 % 100.Oc 88.0 9Ll .. 79.1 C 89.6 d d Dimethoate 0.08% 100.Oc 100.Od IOO.Od 93.8 98.4 b a a a a Fenvalerate 0.01 % 62.2 52.0 42.7 38.7 48.8 Cypermethrin 0.02% 100.Oc 100.Od 100.Od 100.Oe 100.Oe Carbosulfan 0.02% IOO.Oc 100.Od 100:Od 100.Oe 100.Oe Monocrotophos 0.1 % 10O.Oe 10O.Od IOO.Od 100.Oe IOO.Oe Decamethrin 0.0 I % 55.4a 53.3b '54.0b 50.0b 53.0b * Means followed by the same letters are not different statistically (P=0.05) by LSD ~ harmful to theparasitoid. In an earlier study, EASWARAMOORTHY, S., SUBADRA BAI, K., malathion was observed to be extremely toxic KURUP, N.K. and DAVID, H.1986; Survey for the indigenous parasite complex of sugarcane to this parasitoid, when exposed 72 h after scale insect, Melanaspis glomerata (Green). treatment. Similarly, in the case of dimethoate Bharathiya Sug., 12, 63-65. only 25.3 per cent survival was noticed when EASWARAMOORTHY, S., DAVID, H., SAN.: the parasitoids were exposed to 7 days after THALAKSHMI, G., SHANMUGASUN-:­ treatment (Renuka Devi, 1985)indicatlng their DARAM, M., NANDAGOPAL, V. and KURUP, N .K. 1990. Toxicity of certain insecticides' to harmful effects to the parasitoid. Sturmiopsis inferims '. Tns. a larval parasite of sugarcane moth borers. Entomophaga, 35, 130-' ACKNOWLEDGEMENT 136. The authors are thankful to Dr. K. Mohan MANI, M.and KRISHNAMOORTHY, ··A. 1984. Toxicity of some insecticides to Apanteles Naidu, Director, Sugarcane Breeding Institute plutellae a parasite of the diamond back moth. for h~ encouragement and lothe .ICARfor Trop. Pest. Mgmt., 30, 130-132. fundiiIgthe AP Cess Fund Scheme under which MURALIKRISHNA, Y. 1984. Studies on the insec­ this work was carried out. ticidal control. of sugarcane scale insect, Melanaspis glomlwata (G.). M.Sc.(Ag.) Thesis, ··REFERENCES Tamil Nadu Agric. Uniy., Coimbatore. ANONYMOUS, 1989. Final report of ICAR research RENUKA DEVI, T. 1985. Evaluation of some new scheme on biological control of sugarcane scale insectides for the control of sugarcane whitefly, insect using parasites. Sug.Cane Breed. lnstt., Aleurolobus barodensis Mask. and scale insect Coimbatore 125 p. Melanaspis glomerata (Green). M.Phil. Thesis, EASWARAMOORTHY, S. and KURUP, N.K. 1986. Bharathiyar University, Coimbatore. The scale insect, Me Jan asp is glomerata (Green). VARMA, G.C., MANINDER, S. and BRAR, K.S. In: Sugarcane Entomology in India (H. DAVID, 1988. Studies on the effect of insecticides on S. EASW ARAMOORTHY, and R. JAY ANTHI, Trichogramma achaeae Nagaraja and Nagar eds.). S~g. Cane Breed. Instt. PubI. Coimbatore katti (Hymenoptera:Trichogrammatidae). T pp.233-258. Biol.Control, 2, 5-8. EASWARAMOORTHY, S. and SHANMUGASUN­ VENKATESWARA RAO, V. 1983.· Studies· on , DARAM, M. 1991. Techniques for culturing parasite complex of sugarcane scale insect, . hymenopterous parasites. In: Biocontrol tech­ Melanaspis glomerata (Green) (Diaspididae: nology for sugarcane pest management (H. Hemiptera) in two coastal districts of Andhra DAVID and S.