Tomato (Solanum lycopersicum L.) is a vital horticultural crop with economic and nutritional benefits. However, it is vulnerable to pests like the two-spotted spider mite (Tetranychus urticae Koch), which causes significant yield loss and resists many acaricides. Biological control using the phytoseiid mite Neoseiulus longispinosus (Evans) is an eco-friendly alternative. However, the fungicides and pesticides used in tomato cultivation may impact its effectiveness.
The present study was conducted to assess the toxicity of four fungicides viz., copper oxychloride 50% WP (3000 ppm), thiophanate methyl 70% WP (1000 ppm), mancozeb 75% WP (2500 ppm), and metalaxyl 4% + mancozeb 64% WP (2500 ppm) to N. longispinosus and its progeny's fitness against T. urticae. Ten gravid females of N. longispinosus were released onto tomato leaf discs (3cm × 3cm) treated with fungicides in eight replicates by the leaf dip method under laboratory conditions. After 48 hours, cumulative mortality data of N. longispinosus females showed that the fungicide combination metalaxyl + mancozeb caused the highest mortality (60%), followed by mancozeb (52.50%), copper oxychloride (35%), and thiophanate methyl (17.50%). From each treatment and control, 10 surviving predator females were selected and a cohort of 100 predator eggs was collected to further investigate the life table parameters of N. longispinosus on T. urticae. Metalaxyl + mancozeb and mancozeb treatments significantly impacted the life table parameters of N. longispinosus compared to the control, while the effects of copper oxychloride and thiophanate methyl were moderate to negligible.
Thus, N. longispinosus exhibited the ability to withstand the effects of copper oxychloride and thiophanate methyl, while metalaxyl + mancozeb and mancozeb affected its fitness. However, controlled laboratory experiments may not fully account for the influence of biotic and abiotic factors that affect invertebrate fitness under field conditions. Therefore, further field investigations will ascertain the response of the predatory mite to fungicide exposure.
