Predation by Engytatus varians (Distant) adults on different development stages of the prey species Bactericera cockerelli (Sulcer) (egg, second, and third nymphal instars), Spodoptera exigua (Hübner) and Spodoptera frugiperda (J. E. Smith) (egg, first, and second larval instars) was evaluated using tomato (Solanum lycopersicum L.) leaflets or plants. These insects are the primary pest of several agriculturally important crops. The influence of E. varians age on the predation capacity was also analysed. Engytatus varians females consumed significantly more B. cockerelli eggs and nymphs than males. Additionally, female predators consumed significantly more second than third instar prey at two predator ages, while males consumed significantly more the second instar than third instar prey at all predator ages. In most of the cases, females also consumed significantly more S. exigua and S. frugiperda eggs than males; however, in terms of larvae consumption, this difference was observed only in some predator ages. Females consumed more the first than second instar S. exigua than males, whereas this behaviour was only observed in males when the predators were 15 and 17 days old. No significant differences were observed in the consumption of first and second instar of S. frugiperda for both sexes of the predators. Predator age did not cause any systematic effects on the predation rates of any prey species. Based on these results, we confirmed that E. varians has potential as a biological control agent for B. cockerelli and also for the Spodoptera species bioassayed.

Creontiades dilutus (green mirid) and C. pacificus (brown mirid) are major hemipteran pests of transgenic (Bt) cotton in Australia. Current integrated pest management (IPM) guidelines for mirids in Australian cotton, based on economic thresholds and sampling recommendations, were developed and disseminated to industry at the start of the 2005–06 growing season and have remained largely unchanged since then. However, adoption of mirid IPM guidelines by industry has been highly variable and generally well below expectation. Annual surveys of crop protection practices across the Australian cotton industry, from 2010 to 2017, indicate that a third of all mirid sprays are applied below the recommended thresholds each year. More than half of all survey respondents in the 2017 survey indicated lack of confidence in the mirid thresholds due to highly variable and disproportionate damage, a phenomenon best described as the ‘mirid enigma’. A critical review of RD&E outputs since 1998 shows that potential contributors to the mirid enigma include but are not limited to biological, ecological and methodological factors. Mirid feeding damage is likely to vary with developmental stage, gender and reproductive status. Ecological factors including trophic effects and multiple host plant usage are potential modifiers of mirid feeding damage. Methodological and technological constraints and shortcomings are evident in the threshold research done to date. Inadequate commercial sampling that results in unreliable estimates of pest density in the crop is a major contributor to the mirid enigma. Failure to account for the complexity of factors that can influence the nature and severity of mirid damage to cotton often results in fruit loss due to non-mirid related factors being incorrectly attributed to mirids. An alternative approach to mirid management based on modelling the dynamics of net fruit load (production–loss) proposed over 15 years ago is discussed.

Helicoverpa spp. and mirids, Creontiades spp., have been difficult to control biologically in cotton due to their unpredictable temporal abundance combined with a cropping environment often made hostile by frequent usage of broad spectrum insecticides. To address this problem, a range of new generation insecticides registered for use in cotton were tested for compatibility with the assassin bug, Pristhesancus plagipennis (Walker), a potential biological control agent for Helicoverpa spp. and Creontiades spp. Indoxacarb, pyriproxifen, buprofezin, spinosad and fipronil were found to be of low to moderate toxicity on P. plagipennis whilst emamectin benzoate, abamectin, diafenthiuron, imidacloprid and omethaote were moderate to highly toxic. Inundative releases of P. plagipennis integrated with insecticides identified as being of low toxicity were then tested and compared with treatments of P. plagipennis and the compatible insecticides used alone, conventionally sprayed usage practice and an untreated control during two field experiments in cotton. The biological control provided by P. plagipennis nymphs when combined with compatible insecticides provided significant (P<0.001) reductions in Helicoverpa and Creontiades spp. on cotton and provided equivalent yields to conventionally sprayed cotton with half of the synthetic insecticide input. Despite this, the utilization of P. plagipennis in cotton as part of an integrated pest management programme remains unlikely due to high inundative release costs relative to other control technologies such as insecticides and transgenic (Bt) cotton varieties.