African Journal of Biotechnology Vol. 10 (4), pp. 670-674, 24 January, 2011 Available online at http://www.academicjournals.org/AJB DOI: 10.5897/AJB10.023 ISSN 1684–5315 © 2011 Academic Journals Full Length Research Paper Susceptibilities of two populations of Aphis gossiper Glover to selected insecticides H. Tabacian 1, S. Ravan 1 and Ali R. Bandani 2* 1Plant Protection Department, Faculty of Agriculture, University of Zabol, Zabol, Iran. 2Plant Protection Department, College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran. Accepted 14 October, 2010 Two populations of Aphis gossypii were collected from cotton and melon crops treated with insecticides to control this aphid species. The susceptibility of both aphid populations to pymetrozine, Pirimicarb, Oxydemeton-methyl and Imidacloprid was evaluated using leaf deep bioassays in Laboratory which were commonly used to control this aphid on both crops. Results showed that LC 50 values of these insecticides against clones of cotton aphid were 452, 1427, 1810 and 209 ppm, respectively. LC 50 values of the above mentioned pesticides against clones of melon aphid were 625, 688, 523 and 125 ppm, respectively. Lc 50 data showed that aphids reared on melon was 2.07, 1.6 and 3.4 times more susceptible than cotton aphids to Pirimicarb, Imidaclopride and Oxydemeton-methyl and 1.4 times more resistant to Pymetrozine, respectively. In conclusion, it has been shown that clones of cotton aphid is on average 3.4-fold less susceptible to Oxydemeton- methyl, 2-fold less susceptible to pirimicarb, 1.6-fold less susceptible to Imidacloprid and nearly 0.7-fold more susceptible to pymetrozine than clones of melon aphid . There was little difference in susceptibility to pymetrozine between the two populations. It is also suggested that continuous resistance monitoring should be conducted on a regional scale to identify the efficiency of compounds which are applied against this insect species. Key words: Aphis gossypii , cotton, melon, insecticide resistance. INTRODUCTION The melon aphid, Aphis gossypii Glover (Hemiptera: probably some other viruses such as cucumber mosaic Aphididae), is found throughout most of the temperate, virus, watermelon mosaic virus and zucchini yellow subtropic and tropic regions of the world. This insect has mosaic virus (Capinera, 2007). Cotton aphid had the a wide host range feeding on about 700 host plants, potential to develop resistance to insecticides due to high including watermelon, cucumbers, cantaloupes, squash reproductive potential (Mallet and Luttrell, 1991). pumpkin, cotton, citrus, eggplant, pepper, asparagus, Insecticides such as pirimicarb, oxydemton- methyl, bean, beet, potato and okra (Leclant and Deguine, 1994). imidacloprid and pymetrozine are often used to manage Melon aphids suck nutrients from the plant causing A. gossypii in the cotton and the other crops. Imidacloprid foliage to become chlorotic and die. Also, their feeding acts on the nicotinic acetylcholine receptor, causing the causes distortion and leaf curling, interfering with photo- insect to reduce or stop feeding and reduces mobility synthetic capacity of the plant. Moreover, this insect (Boiteau and Osborn, 1997). Pymetrozine impacts species secretes honeydew which provides a growing feeding behavior (Harrewijn and Kayser, 1999). Pirimi- media for saprophytic fungi ( Capnodium spp Cladosporium carb, a selective aphicides and Oxydemeton- methyl both spp and Fumago spp) on plant tissues (Hillocks and act as an acetylycholinesterase inhibitor (Mooress et al., Bretell, 1992). Melon aphid transmits potyviruses and 1996; Menozzi et al., 2004). Intensive use of insecticides often leads to resistance development by sprayed aphids, forcing farmer to in- crease dosage of application frequency. Resistances of *Corresponding author. E-mail: [email protected]. Tel: +98 261 A. gossypii to some insecticide have been reported 2818705. Fax: +98 261 2238529. (Andrew et al., 2006; Wang et al., 2002). Mechanisms in Tabacian et al. 671 Table 1. Concentrations (ppm) used in the experiments for all four insecticides against two populations (melon aphid and cotton aphid) of A. gossypii . Concentration tested (ppm) Recommended Insecticide type Cotton aphid Melon aphid dosage (ppm) 500,1000,2000,4000, 8000 250,500,1000,2000, 4000 500 - 700 Pirimicarb 500,1000,2000,4000,8000 125,250,500,1000,2000 1000 Oxydemton-metyl 44,87,175,350,700 42,85,175,350,700 250 Imidacloprid 125,500,1000,2000,4000 125,500,1000,2000,4000 1000 Pymetrozine which Insects develop resistance to insecticides include Leaf dip assays were performed according to the procedures decrease in insecticide penetration through cuticle which described by Bandani and Butt (1999).. Initially, for each insecticide reduce target site sensitivity and enhance metabolism on each population, bracketing test was done to determine doses that produce satisfactory range (10 - 90% mortality). The used (Plapp, 1976; Oppenoorth, 1984); Enhancement of concen-trations were given in Table 1. chemical metabolism, decreasing the effective amount of All four insecticides were diluted with distilled water and each insecticides that can kill insects. Cytochrome P450 assay consisted of 25 apterous adult per treatment (each dose) and monooxygenases, glutathione S-transferases and este- each treatment replicated 5 times. Plant leaf was cut (three weeks rases are the major detoxifying enzymes that are old seedlings leaf) and dipped into insecticide solution for 10 s and allowed to dry for 30 min before exposing the insects to it. For involved in insecticide resistance (Oppenoorth, 1984). controls, plant leaves were treated with distilled water alone. Mortality In recent years there are complains about insufficient was assessed after 48 h. Mortality data were corrected with control results of available chemicals on both melon and Abbott’s formula (Abbot, 1925). cotton aphids. So, the aim of the current study was to evaluate susceptibilities of two populations of A. gossypii to insecticides used for control of this aphid species in Data analysis Iran. These insecticides are from four different insecticide In these experiments, concentration-mortality regression for the groups including pirimicarb, oxydemeton- methyl, imida- adult from each bioassay was evaluated statistically using probit cloprid and pymetrozine. So, the efficacy of these analysis (Polo-PC Probit and Logit analysis; LeOra Software 1997) insecticides on two populations of A. gossypii , reared on to determine the lethal concentrations (LC 50 s). Differences in cotton and melon were investigated to determine these toxicity were considered significant when 95% Fiducial Limit (FL) insecticides effectiveness on the A. gossypii control. did not overlap (Adams et al., 1990). Unavailability of known sus- ceptible strain of A. gossypii has led comparison of LC 50 between Bioassays using treated leaf disks were used to two populations that had collected from cotton and melon fields and determine dose response curves for both populations. reared on them. MATERIALS AND METHODS RESULTS Insect rearing Susceptibilities to imidacloprid (Confidor®) A. gossypii used in these experiments were collected from melon Toxicity of imidacloprid against A. gossypii obtained and cotton farms of Torbat Jam, Iran. Two aphid colonies were originally from melon and cotton is illustrated in Table 2. established separately on Cucumis melo var khatooni and on Lethal toxicity (LC ) of imidacloprid to aphid was 125 Gossypium hirsutum var varamin in greenhouse at 20 ± 2°C, a 16 h 50 light: 8 h dark cycle and relative humidity of 55 ± 5% as described ppm and to cotton aphid was 209 ppm. There was a 1.67 by (Lashkari et al., 2008). These colonies were kept on each fold increase in response values (Table 2) that it shows rearing plants for several generations. Every week (5 - 7 days) that average LC 50 for cotton aphid was 1.67 fold more plants were replaced with new ones in order to keep colonies alive. than melon aphid. However, there was considerable Apterous adults from these colonies were used in this study. overlap between individual values that it means there Seedlings used for aphids culturing as well as producing leaf disks were not significant differences in tolerance to the insec- for insecticide bioassays were grown in plastic pots in above mentioned conditions. ticide. Both species are susceptible to imidacloprid but comparing the responses of the two clones showed that clones of cotton aphid were moderately more tolerant to the Toxicity bioassay insecticide compared with those clones of melon aphid. Four insecticides used in this experiment were Pirimicarb 50% WP (China's Jecom Company), Pymetrozine 25% WP (Iran's Susceptibilities to oxydemeton-methyl (Metasystox- Moshkfaamfars Company), Imidacloprid (Confidor®) 35% SC R®) (German's Bayer Company) and Oxydemton-methyl (Metasystox- R®) 25% EC (German's Bayer Company). Average LC 50 values ranged from 1810 ppm for cotton 672 Afr. J. Biotechnol. Table 2. Susceptibility of two populations (melon and cotton aphids) of A. gossypii to imidacloprid based on probit analysis of mortality after 48 h. 2 Slop ± SE X (df) N. Imidacloprid LC 50 LC 90 Aphid population 1 ± 0.1 14.1(3) 750 673(333 - 7339) 125)43 - 231) Melon aphid 1 ± 0.1 10.8(3) 750 1025(531.5 - 5680) 209(121 - 358) Cotton aphid LC values are based on ppm; values in parenthesis show Fiducial Limit (FL); N: number of insects treated. Slope: derived from regression equation of mortality values. SE: standard error. Table 3. Susceptibility of two populations (melon and cotton aphids) A. gossypii to oxydemton-metyl based on probit analysis of mortality after 48 h. 2 Slop ± SE X (df) N. Oxydemton-metyl LC 50 LC 90 Aphid population 1 ± 0.2 1.7(3) 750 2521(1938 - 3622) 523(424 - 628) Melon aphid 0.9 ± 0.2 6.7(3) 750 7296(4587 - 18489) 1810(1062 - 2672) Cotton aphid LC values are based on ppm; values in parenthesis show Fiducial Limit (FL); N: number of insects treated. Slope: derived from regression equation of mortality values. SE: standard error. Table 4. Susceptibility of two populations (melon and cotton aphid) A. gossypii to pirimicarb based on probit analyses of mortality after 48 h.