Field efficacy and economic viability of entomopathogenic fungal products for managing the tomato leafminer (tuta absoluta) in Uganda
Management of the invasive tomato leafminer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) has primarily relied on increased application of hazardous synthetic chemical pesticides with limited success. The use of entomopathogens has been advanced among safer and more sustainable management options. The field efficacy of candidate fungal isolates, Metarhizium anisopliae ICIPE 20, M. anisopliae ICIPE 69 (Campaign®) and Dudu Acelamectin (positive check) was evaluated against T. absoluta on tomato through inundative application. Experiments with treatments laid in Randomised Complete Block Design and replicated thrice, were conducted during cropping seasons April – July, 2019 (first season) and December, 2019 – March, 2020 (second season) at Mukono Zonal Agricultural Research & Development Institute, Mukono district in Uganda. Tuta absoluta incidence, injury severity on leaves and fruits, fruit yield loss, and economic viability of test treatments were assessed. Results showed generally reduced injury severity and significantly lower fruit yield loss in treated plots compared to untreated plot in both seasons. Tomato fruit yield was higher in treated plots than the untreated plot. The marketable fruit yield gain for Dudu Acelamectin, M. anisopliae ICIPE 20 and M. anisopliae ICIPE 69 treatments was respectively 130.15, 72.14 and 55.3% during first season, and 41.21, 22.01 and 15.85% during second season. The three respective treatments had Benefit cost ratio (BCR) of 8.92, 4.31 and 3.43 during first season, and 6.30, 2.84 and 2.14 during second season. The treatments showed a degree of effectiveness and economic viability in controlling T. absoluta on tomato in the field. However, the efficacy of M. anisopliae ICIPE 20 and ICIPE 69 should be assessed further at different agro-ecological zones, dosages, formulations, large scale, and their compatibility with the pesticides commonly used in tomato production systems.