Toxicity and sub-lethal effects of temephos, lambda-cyhalothrin and cypermethrin on predatory insect Diplonychus rusticu
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ORIGINAL RESEARCH ARTICLE
Toxicity and sub-lethal effects of temephos, lambda-cyhalothrin and cypermethrin on predatory insect Diplonychus rusticus Fabricius (Hemiptera: Belostomatidae) Appadurai Daniel Reegan 1,2
&
Bosvin Ben Bentrock 1 & Antony Cruz Asharaja 3 & Samuel Tennyson 1 & Rajasingh Raveen 1
Received: 6 June 2019 / Revised: 1 September 2020 / Accepted: 18 September 2020 # African Association of Insect Scientists 2020
Abstract Diplonychus rusticus (Heteroptera: Belostomatidae) is relatively a bigger sized tropical water insect serves as a main predator of mosquito larvae. In the present study, toxicity and effects of three different insecticides viz., temephos, lambda-cyhalothrin and cypermethrin was evaluated on D. rusticus. The results showed that the cypermethrin exhibited highest toxicity with lowest LC50 and LC90 values of 0.02 and 0.12 ppm on D. rusticus. Observations showed that the functional response greatly varied with all the three insecticides. The mean number of preys consumed at the density of 64 larvae was significantly different among the treatments. The mean longest handling time of 4.18 ± 0.34 and the mean lowest attack rate of 0.015 ± 0.008 were observed in lambda-cyhalothrin and cypermethrin treatments, respectively. The adult longevity of D. rusticus was found to be very less (42.33 ± 1.52 days) in cypermethrin treatments, whereas it was 113 ± 1.73 days and 120 ± 2.64 days in lambda-cyhalothrin and temephos insecticides, respectively at 0.01 concentration. The coupling behavior of the insect was noted to occur very rarely in all the three insecticide treatments. The total number of eggs layed was 16 eggs and 26 eggs in lambda-cyhalothrin and temephos treatments at 0.01 concentration, respectively. Furthermore, it was noted that there are no eggs were hatched (0%) from these egg clusters. These results indicate that the tested insecticides exhibited sub-lethal effects on the predatory insect D. rusticus. Keywords Conservation biological control . Diplonychus rusticus . Insecticide effects
Introduction Vector-borne diseases are emerging and resurging as serious public health problems (Swei et al. 2020). Mosquitoes plays a major role as vectors of many diseases such as filariasis, malaria, dengue, chikungunya, Japanese encephalitis and zika (Reegan et al. 2016). They cause mortality and morbidity resulting in economic loss and social problems in many developing and under-developed countries (Reegan et al. 2014a, b). Currently, climate change and unplanned urbanization are * Appadurai Daniel Reegan [email protected] 1
Department of Zoology, Madras Christian College, Chennai 600059, India
2
Present address: National Centre for Disease Control, NTI Campus, Bellary road, Bangalore 560003, India
3
P.G. and Research Department of Zoology, Pasumpon Muthuramalinga Thevar College, Tenkasi, Tamil Nadu 627953, India
enhancing human exposure to mosquitoes (Githeko et al. 2000; Monaghan et al. 2018). Further, the development of insecticide resistance in disease vectors is also a ma
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