Abstract
Rhynocoris longifrons (Hemiptera: Reduviidae) is a generalist predator of many cotton insect pests. The hiding behaviour of this predator, which is one of the key factors of predation success, was investigated under screen house conditions. Moreover, we evaluated its biocontrol potential against Aphis gossypii (Hemiptera: Aphididae), Dysdercus cingulatus (Hemiptera: Pyrrhocoridae), Phenacoccus solenopsis (Hemiptera: Pseudococcidae), and Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) under screen house and field conditions. Results showed that R. longifrons life stages preferred to hide under small pebbles in the screen house tests. All the R. longifrons life stages showed a biocontrol potential against the four insect pests under screen house conditions. However, their biocontrol potential had not varied in relation to day and night hours. Augmentative releases of R. longifrons were carried out for two seasons such as South-west monsoon, 2011 and post-monsoon, 2012. The augmentative release of R. longifrons reduced significantly insect pests on cotton. In fact, the release of this predator in cotton fields was capable to reduce the population of H. armigera (50%), P. solenopsis (28%), D. cingulatus (18.8%), and A. gossypii (11.8%) during the rain fed condition (south-west monsoon season). During irrigated condition (post-monsoon season), populations of D. cingulatus were reduced by 26%, than P. solenopsis (20.6%), and A. gossypii (16.8%). Except ants, no negative impact was reported on other natural enemies present in the cotton field. Significantly higher crop yield and cost benefit ratio was observed in the predator release plots indicating that R. longifrons can be used in an integrated pest management program for multiple cotton pests.
Highlights
Cotton (Gossypium hirsutum L., Malvaceae), is an important cash crop throughout the world
No significant differences in the predation rate of R. longifrons life stages was recorded on A. gossypii (F = 1.022, df = 23, p ≥ 0.05), D. cingulatus (F = 1.410, df = 23, p ≥ 0.05), P. solenopsis (F = 0.794, df = 23, p ≥ 0.05), and H. armigera (F = 1.092, df = 23, p ≥ 0.05) during dawn hours
When we considered total predation rate, no significant difference of predation rate was observed between R. longifrons life stage when feeding on D. cingulatus (F = 1.422, df = 47, p ≥ 0.05), P. solenopsis (F = 1.081, df = 47, p ≥ 0.05), and H. armigera (F = 0.839, df = 47, p ≥ 0.05)
Summary
Cotton (Gossypium hirsutum L., Malvaceae), is an important cash crop throughout the world. Reduviids are common in cotton agro-ecosystems[10,11] They often fail to colonize fields to provide effective control of the pests. Specific information on the predatory behaviour and biological control potential of R. longifrons against any pests under field conditions has not been widely reported. The predator can exhibit a variety of necessary adaptations for predation as well as survival[28] One such important adaptation is a hiding behavior, either to escape from natural enemies and/or to find shelter. The specific objectives of this study were to: 1) understand R. longifrons hiding behaviour under open field conditions, 2) evaluate their biocontrol potential in relation to day and night hours, 3) test their efficacy in an augmentative release program under field conditions for two seasons, and 4) estimate the cost benefit ratio and percent avoidable loss
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