Potential of Metarhizium Anisopliae in the Management of Tomato Borer (Tuta Absoluta) Infesting Tomato

Abstract

Greenhouse experiments were conducted consisting of 5 treatments: Metarhizium anisopliae (6.0 x 103 cfu /ml) formulated with Nonylphenol ethoxylate, Metarhizium anisopliae (6.0 x 103 cfu /ml) conidia alone, Nonylphenol ethoxylate alone, compared to a standard pesticide having Indoxacarb 85g/L and Emmamectin benzoate 15g/L. The field experiment consisted of Metarhizium anisopliae (6.0 x 103 cfu /ml) in Nonylphenol ethoxylate, Metarhizium anisopliae (6.0 x 103 cfu /ml) conidia alone, Nonylphenol ethoxylate alone and a standard pesticide Indoxacarb 85g/L with Emmamectin benzoate 15g/L. Rio grande variety had the largest leaf area in the two seasons but this was comparable with that recorded for M82, Eden, Cal J and Moneymaker. The evaluated tomato varieties retained viable conidia of Metarhizium anisopliae on their leaves but Rio grande variety significantly (p<0.05) retained the most colonies. Adjuvants, Nonylphenol ethoxylate 15% and Tween 80 significantly (p<0.05) increased the radial growth of Metarhizium anisopliae ICIPE 69 and ICIPE 78 isolates, compared to control whereas liquid soap significantly (p<0.05) prevented the radial growth of Metarhizium anisopliae ICIPE 69 and ICIPE 78 isolates at all concentrations when compared to control. Greenhouse experiments were conducted consisting of 5 treatments: Metarhizium anisopliae (6.0 x 103 cfu /ml) formulated with Nonylphenol ethoxylate, Metarhizium anisopliae (6.0 x 103 cfu /ml) conidia alone, Nonylphenol ethoxylate alone, compared to a standard pesticide having Indoxacarb 85g/L and Emmamectin benzoate 15g/L. The field experiment consisted of Metarhizium anisopliae (6.0 x 103 cfu /ml) in Nonylphenol ethoxylate, Metarhizium anisopliae (6.0 x 103 cfu /ml) conidia alone, Nonylphenol ethoxylate alone and a standard pesticide Indoxacarb 85g/L with Emmamectin benzoate 15g/L. xiv Rio grande variety had the largest leaf area in the two seasons but this was comparable with that recorded for M82, Eden, Cal J and Moneymaker. The evaluated tomato varieties retained viable conidia of Metarhizium anisopliae on their leaves but Rio grande variety significantly (p<0.05) retained the most colonies. Adjuvants, Nonylphenol ethoxylate 15% and Tween 80 significantly (p<0.05) increased the radial growth of Metarhizium anisopliae ICIPE 69 and ICIPE 78 isolates, compared to control whereas liquid soap significantly (p<0.05) prevented the radial growth of Metarhizium anisopliae ICIPE 69 and ICIPE 78 isolates at all concentrations when compared to control. The findings of the laboratory assays show that Metarhizium anisopliae significantly (p<0.05) caused mortality to Tuta absoluta larvae. One hundred percent (100% ) mortality of Tuta larvae was achieved within 36 hrs of treatment of larvae treated with Metarhizium anisopliae 1.2 x 106 cfu /ml. Metarhizium anisopliae 1.2 x 103 cfu /ml , 1.2 x 104 cfu /ml and 1.2 x 106 cfu /ml did not differ in effect 60hours after treating the larvae. In the greenhouse experiment, no differences were noticed in the population of larvae in the different treatments except in the 8th week where Metarhizium anisopliae & NPnEO recorded the least mean population of larvae and was significantly (P<0.05) lower than control but comparable with the rest of the treatments. The resultant yield recorded show that the standard pesticide, Indoxacarb 85g/L and Emmamectin Benzoate 15g/L, significantly (p<0.05) had the highest yield compared to control but it was comparable to the second highest yield recorded in Metarhizium anisopliae & NPnEO. Control had the most larval population, most damaged tomatoes and lowest yield recorded which were significantly (p<0.05) different from the treated tomatoes. In the open field, Indoxacarb 85g/L and Emmamectin Benzoate 15g/L had the least mean population recorded which was significantly different (p<0.05) from control but not from Metarhizium anisopliae and Nonylphenol ethoxylate xv 15% treatment with the second lowest population. The resultant yields were significantly (p<0.05) higher compared to control with the least damage percentage of the fruits in both Indoxacarb 85g/L and Emmamectin Benzoate 15g/L and Metarhizium anisopliae and Nonylphenol ethoxylate 15% treatments. Metarhizium anisopliae can be used to manage T. absoluta under field and greenhouse conditions and that Nonylphenol ethoxylate 15% and Tween 80 as adjuvants can be used to formulate and facilitate distribution of the conidia and enhance growth for fast establishment on the crop.