Bio-pesticides for the Control of Two–spotted Spider Mite, Tetranychus urticae Koch, in Strawberry Cultivations

Abstract

Strawberry is cultivated in polytunnels and open field cultivations in Nuwara Eliya district. Recently, a severe infestation of the Two Spotted Spider Mite (TSSM) in strawberry was reported and the farmers observed Department of Agriculture (DOA) recommended insecticide Abamectin was ineffective. Therefore, two Biopesticides; M-Impact and Hort-Impact were tested in three locations of Jagro Farms Ltd, Nuwara Eliya to control TSSM. Two rates of Bio-pesticides were tested in nursery, vegetative and fruiting stages in a randomized complete block design. Results showed that the average percentage mortality of TSSM at day after each application of Hort-Impact was 95.4 for both concentrations. M-Impact resulted an average mortality of 98.7% and 97.9% for 1.0 mLL-1 and 0.5 mLL-1, concentrations respectively during the vegetative stage at Meepilimana. However, at Radella, during the nursery stage, average mortalities were 98.4% and 98.3% for 1.0 mLL-1 concentration and 95.8% and 97.7% for 0.5 mLL-1 concentration for Hort-impact and M-impact, respectively. The DOA recommended insecticide Abamectin at 1.0 mLL-1 concentration resulted a mean TSSM count >200 at the end of the experiment and was significantly higher than Hort-Impact and M-Impact treatments. The TSSM counts were 52 and 45 and 80 and 36 for concentrations 1.0 mLL-1 and 0.5 mLL-1 respectively at Meepilimana and a similar trend was observed at Radella. It is therefore concluded that both Bio-pesticides at both concentrations were effective in controlling TSSM in strawberry. However, M-Impact cannot be used at fruiting stage as it imparts a bitter taste for the fruits at Welimada site.