Abstract
Susceptibility of Tuta absoluta Meyrick (Lepidoptera: Gelechiidae) populations to Metarhizium anisopliae and Bacillus thuringiensis (Bt) were evaluated under laboratory conditions. T. absoluta larvae were treated either individually or in combination with a single dose rate of B. thuringiensis (0.5 μL/L) and three conidial suspensions viz. 1x104, 1x106 and 1x108 spores/mL of M. anisopliae. Larval mortality, pupation, adult emergence, mycosis and sporulation varied depending on the application of different quantities of M. anisopliae alone and in combination with B. thuringiensis. Maximum mortality (100%) was achieved in 2nd instar larvae when M. anisopliae (1x108 spores/mL) and B. thuringiensis (0.5µL/L) were applied synergistically,while 4th instar larvae recorded a 95.45% mortality. Compared with the untreated checks, mortality, pupation and adult emergence of both 2nd and 4th instar larvae were significantly reduced with the combined application of M. anisopliae (1x108 spores/mL) and B. thuringiensis (0.5µL/L). Μycosis was most prevalent on 2nd and 4th instar larvae, exceeding 88 and 80% respectively,after exposure to 1×104 conidia/mL. The results indicate that the entomopathogenic fungi and the insecticidal protein produced by B. thuringiensis can be used in combination as biocontrol agents for the management of T. absoluta.
Highlights
Tomato (Solanum lycopersicum L.) is one of the most popular and nutritious vegetable crops in Greece
Larval Mortality A high mortality trend of T. asboluta larvae was observed in the combined treatments of M. anisopliae and B. thuringiensis, and as the dose rate increased
The maximum recorded mortality was followed by a mortality of 80.18% and 71.76% of 2nd and 4th instar larvae respectively, in Ma2 and B. thuringiensis combination treatments
Summary
Tomato (Solanum lycopersicum L.) is one of the most popular and nutritious vegetable crops in Greece. Application of synthetic insecticides has increased and remains the most common pest control strategy. Chemical control is difficult due to the rapid development of pest resistance to insecticides as well as due to the negative impact on natural enemies, the environment and human health. Considering all the above factors, the scientific community has increased its interest in alternative control methods and Integrated Pest Management approaches.[1,2,3]. Among the possible methods for the management of Tuta absoluta,[4,5,6,7] which is a key pest of tomato, the use of entomopathogenic microorganisms provides an alternative to chemical insecticides with increased environmental safety and pest selectivity; they can be used either alone or in combination with other pest control tactics. The entomopathogenic fungus Metarhizium anisopliae and the bacterium Bacillus thuringiensis have an important role in crop protection, and may represent effective and ecologically sound solutions to pest problems.[9,10]
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