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Relative Toxicity of Some Insecticides Against the Greenhouse Whitefly Trialeurodes Vaporariorum (Hemiptera: Aleyrodidae)

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Relative Toxicity of Some Insecticides Against the Greenhouse Whitefly Trialeurodes Vaporariorum (Hemiptera: Aleyrodidae) Indian Journal Of Natural Sciences www.tnsroindia.org. © IJONS Vol.6 / Issue 31 / August 2015 International Bimonthly ISSN: 0976 – 0997 RESEARCH ARTICLE Relative Toxicity of some Insecticides against the Greenhouse Whitefly Trialeurodes vaporariorum (Hemiptera: Aleyrodidae) Nisha Devi*, KC Sharma and RS Chandel Dr Y.S. Parmar University of Horticulture and Forestry, Department of Entomology & Apiculture, Nauni, Solan, Himachal Pradesh 173230, India. Received: 12 May 2015 Revised: 25 Jun 2015 Accepted: 31 Jul 2015 *Address for correspondence Nisha Devi Dr Y.S. Parmar University of Horticulture and Forestry, Department of Entomology & Apiculture, Nauni, Solan, Himachal Pradesh 173230, India. E-mail: [email protected] This is an Open Access Journal / article distributed under the terms of the Creative Commons Attribution License (CC BY-NC-ND 3.0) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. All rights reserved. ABSTRACT Relative toxicity of imidacloprid, acetamiprid, thiamethoxam, diflubenzuron and two Horticulture Mineral Oils viz., SERVO and ESSO were evaluated against the second instar nymphs of the greenhouse whitefly, Trialeurodes vaporariorum Westwood infesting tomato under laboratory conditions. All the test insecticides and HMO’s caused significant and dosage dependent mortality. The LC50 values calculated for imidacloprid, acetamiprid, thiamethoxam, diflubenzuron, ESSO and SERVO were 0.016, 0.019, 0.041, 0.067, 0.28 and 0.35 per cent, respectively. LC90 for these insecticides were 0.20, 0.23, 0.34, 0.53, 2.65 and 2.74 per cent, respectively. On the basis of these studies imidacloprid was found to be the most toxic insecticide followed by acetamiprid, thiamethoxam and diflubenzuron. Among HMO’s, ESSO was comparatively more effective against the greenhouse whitefly but caused phytotoxicity at 1% concentration whereas SERVO caused phytotoxicity at 1 % and 0.5 % to tomato leaves under laboratory conditions. Key words: Insecticide, Trialeurodes vaporariorum, toxicity INTRODUCTION Growing crops in greenhouses is faced by several challenges, among them, the infestation by pests and diseases is the fore for most which not only reduce the quantity of the product but reduces the yield to a greater extent. Among 8791 Indian Journal Of Natural Sciences www.tnsroindia.org. © IJONS Vol.6 / Issue 31 / August 2015 International Bimonthly ISSN: 0976 – 0997 Nisha Devi et al. these the greenhouse whitefly Trialeurodes vaporariorum Westwood (Hemiptera: Aleyrodidae)is the most serious (Van Lenteren and Noldus, 1990). Whiteflies feed voraciously on the plant sap and in sufficient numbers, cause leaf drop and prohibit the maturing of fruits. They produce sticky honeydew which damages crops and serves as a substrate on which sooty mould (a black fungus) grows, thereby prohibiting normal respiration of leaves, reducing photosynthesis and rendering plant products unattractive. In addition to damage caused by direct feeding pressure, whiteflies transmit plant viruses also (Gerling, 1990). There are different pest control tactics, but the most common and quicker one is that of chemical control which is generally adopted by our farming community. Among these neonicotinoids are the insecticides with wide spectrum effect against sucking and certain chewing insect pests (Jeschke and Nauen, 2008). On the other hand, HMO’s are widely used against the pests of orchards, yet their use in vegetable crops are limited. Horticultural oils (e.g., SunSpray) are one of the most effective whitefly controls available for use on house plants. Applied as dilute sprays (e.g., 2 percent), they smother the immature forms and eggs (http://www.ext.colostate.edu/pubs/insect/05569.pdf). In view of this the present studies were undertaken to evaluate the efficacy of some neonicotinoides (imidacloprid, acetamiprid, thiamethoxam), diflubenzuron and HMO’s against the greenhouse whitefly so that the information thus gathered may be utilized in managing the population of this pest. MATERIAL AND METHODS Raising of stock culture:A stock culture of the greenhouse whiteflies was raised under laboratory conditions on tomato plants, which were planted in earthen pots (25 cm X 20 cm) and plastic cups (7 cm X 7.5 cm). Six insecticides viz., imidacloprid (Midas 17.8 % SL), acetamiprid (Pride 20 % SP), thiamethoxam (Actara % 25 WG), diflubenzuron (Diflubenzuron 20 % SC) and two HMO’s (ESSO and SERVO) were evaluated for their toxicity against the greenhouse whitefly. Stock solutions of 0.1 % of each insecticides and 1 % of HMO’s was prepared. Desired concentrations of the test insecticides were prepared from the stock solutions. Intrinsic toxic studies: The intrinsic toxicity of the test insecticides was evaluated under laboratory conditions against the second instar nymphs of the greenhouse whitefly. The bioassay was carried out as per the procedure given below: Tomato leaves having second instars of greenhouse whitefly were dip-treated in each test concentration for 30 seconds. Treated leaves were then air dried and placed on a filter paper in petri plates. A cotton boll soaked in water was placed at the base of each filter paper for hydration of leaves (García-Mateos et al., 2007). For each concentration, 5 replicates were prepared along with an equal number of replicates in untreated (emulsified water, 0.05 %) control. The mortality data were recorded after 48 hours. Concentration-mortality relationship data for the nymphal stage was calculated by recording the mortality range of 20-80 per cent for each insecticide. The LC50 and LC90 values were calculated by subjecting the mortality data to probit analysis (Finney, 1971) after applying Abbott’s correction (Abbott, 1925). Phytotoxic studies Phytotoxicity studies of HMO’s with imidacloprid and acetamiprid on tomato leaves was recorded to evaluate their individual and combined effect on the tomato and gerbera plant. A stock solution of 0.1 % of the test insecticides and 1 % HMO’s was prepared and further dilutions were made as per the desired concentrations. Symptoms were observed after 24 hours and 48 hours. 8792 Indian Journal Of Natural Sciences www.tnsroindia.org. © IJONS Vol.6 / Issue 31 / August 2015 International Bimonthly ISSN: 0976 – 0997 Nisha Devi et al. RESULTS AND DISCUSSION Intrinsic toxic studies : The studies revealed that imidacloprid when applied at 0.1 %, 0.05 %, 0.025 %, 0.0125 %, 0.00625 % and 0.00312 5% by leaf-dip method resulted in 82.69, 72.01, 61.03, 50.80, 39.30 and 25.39 per cent mortality, respectively of greenhouse whitefly nymphs. In control, where nymphs were treated with emulsified water (0.05 %) only 11.04 per cent mortality was recorded. After correcting the mortality data and subjecting to probit analysis LC50 and LC90 values of 0.016 % (fiducial limits: 0.011 and 0.022 % conc.) and 0.20 % (fiducial limits: 0.10 and 0.36 % conc.) respectively. Acetamiprid at concentration ranging from 0.003125 to 0.1 % killed the treated insects in concentration dependent manner from 25.39 to 81.69 per cent. On subjecting the data to probit analysis, the LC50 value was calculated to be 0.019 % with fiducial limits of 0.013 and 0.025 %. The LC90 value was 0.23% with fiducial limits of 0.12 and 0.46 %. The nymphs when treated with thiamethoxam at concentration varying from 0.00625 to 0.2 % gave dosage dosage dependent mortality of 21.26 to 85.28 per cent as against 11.04 per cent in the control. Probit analysis of the data revealed that LC50 and LC 90 values of thiamethoxam were 0.041 % (fiducial limit: 0.031 and 0.054) and 0.34 % (fiducial limit: 0.20 and 0.58), respectively. Diflubenzuron at concentration varying from 0.0125 to 0.2 % gave dosage dependent mortality of 25.45 to 81.42 per cent. After correcting the mortality data using Abbott’s correction and subjecting to probit analysis, a median lethal concentration of 0.067 % (fiducial limit: 0.051 and 0.089 %) was obtained. The concentration of diflubenzuron required to kill 90 per cent of the test population was 0.53 % (fiducial limit: 0.28 and 0.98%). Among Horticulture mineral oils, in SERVO, mortality ranged from 23.13 to 74.53 % at concentrations varied from 0.0625 to 1.00 %. the LC50 value was calculate to be 0.35 % (fiducial limits; 0.27 and 0.47 %) whereas, LC90 value was 2.74 % (fiducial limit: 1.41 and 5.37 %). ESSO when applied at concentration range 0.0625 to 1.00 % resulted in 25.48 to 76.69 per cent mortality of the nymphs of T. vaporariorum. On subjecting the data to probit analysis the LC50 and LC90 values were 0.28 % (fiducial limit: 0.20 and 0.39 %) and 2.65 % (fiducial limit: 1.23 and 5.62 %), respectively (Figure1). Taking the toxicity of SERVO as unity (1.0), the relative toxicity of imidacloprid, acetamiprid, thiamethoxam, diflubenzuron and ESSO was 21.9, 18.4, 8.5, 5.2 and 1.3, respectively. Phytotoxic studies of HMO’s revealed that SERVO caused phytotoxicity with acetamiprid and imidacloprid at the concentration of 1 % oil + 0.1 % insecticide and 0.5 % oil + 0.05 % insecticide. ESSO caused phytotoxity only with imidacloprid at the conc. of 1 % oil + 0.1 % insecticide (Table 2). No phytotoxic effect was observed at LC50 value of these insecticides. The studies on the evaluation of these insecticides revealed a variable response against the second instar nymphs of whitefly which may be due to the variability in neonicotinoids characteristics influencing the movement in plant tissues such as water solubility which greatly affecting their toxicity especially against those insects having piercing and sucking mouth parts such as whitefly (Cloyd and Bethke, 2011). The present studies find support with those of Muhammad Amjad et al., (2009) who reported that acetamiprid (Megamos 20 SL) was the most effective insecticides against the cotton whitefly, Bemesia tabaci at recommended dose (150 ml/acre) followed by imidacloprid (Conifidor 200 SL) and thiamethoxam (Actara 25 WG) with 250 ml/acre and 24 gm/acre recommended dose, respectively.
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