Abstract. The Cotton Catchment Communities Cooperative Research Centre began during a period of rapid uptake of Bollgard II ® cotton, which contains genes to express two Bt proteins that control the primary pests of cotton in Australia, Helicoverpa armigera and H. punctigera. The dramatic uptake of this technology presumably resulted in strong selection pressure for resistance in Helicoverpa spp. against the Bt proteins. The discovery of higher than expected levels of resistance in both species against one of the proteins in Bollgard II ® cotton (Cry2Ab) led to significant re-evaluation of the resistance management plan developed for this technology, which was a core area of research for the Cotton CRC. The uptake of Bollgard II ® cotton also led to a substantial decline in pesticide applications against Helicoverpa spp. (from 10-14 to 0-3 applications per season). The low spray environment allowed some pests not controlled by the Bt proteins to emerge as more significant pests, especially sucking species such as Creontiades dilutus and Nezara viridula. A range of other minor pests have also sporadically arisen as problems. Lack of knowledge and experience with these pests created uncertainty and encouraged insecticide use, which threatened to undermine the gains made with Bollgard II ® cotton. Here we chronicle the achievements of the Cotton CRC in providing the industry with new knowledge and management strategies for these pests.

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Here we review the current knowledge of green mirids, Creontiades dilutus (Hemiptera: Miridae). Creontiades dilutus are highly polyphagous pests that are endemic to Australia. They are widely distributed across Australia and feed on a broad range of agricultural crops. Recently, C. dilutus has become an important focus of pest control in Australian cotton crops, most likely due to a decrease in insecticide use associated with the widespread uptake of transgenic cotton varieties. Prior to this, C. dilutus had been coincidentally controlled in cotton by applications of insecticides targeted at other pests such as Helicoverpa spp. Further, the pest status of C. dilutus in summer pulse crops has become more apparent due to the increased research dedicated to this area over the past decade. We review various aspects of the biology and ecology of C. dilutus, including their life cycle, feeding behaviour and host plants. We also examine current control methods and laboratory-rearing techniques, which will be important for the development of novel control strategies in cotton and other cropping environments. Possible future research directions are highlighted, such as dispersal capabilities and extent of genetic structure within C. dilutus populations, as these will have important implications for effective and sustainable control in the future.

The egg and nymphal development, fecundity and survival of the green mirid, Creontiades dilutus were examined at a range of temperatures and a modified day-degree model fitted to the data. Day degree (DD) requirements for egg and nymphal development, and threshold temperatures were calculated from the fitted lines. Female fecundity and longevity, egg and nymphal development, and survival of C. dilutus were significantly influenced by temperature. Eggs and nymphs failed to complete development at temperatures below 17 and at 38°C. Females also failed to produce any eggs at 11 and 38°C. The optimum temperature range for female fecundity was found to be 26-32°C. The optimum temperature for the development of eggs was calculated from the model as 30.5°C and for nymphs as 31.5°C. The threshold temperature for development was 15.8°C for egg and 15.1°C for nymph; 69.4 and 156.7 DD were required for completing the egg and the nymphal development, respectively. At the optimum temperature, it was estimated that development from egg to adult took 15 days. Survival was highest at 26°C for eggs and at 30-32°C for nymphs.

The efficacy of commercially available chemical insecticides and biopesticides on the cotton mealybug (CMB), Phenacoccus solenopsis, was evaluated in the glasshouse. Spirotetramat, sulfoxaflor and buprofezin were identified as key insecticides for use in integrated pest management (IPM) strategies aimed at controlling CMB without flaring other co-occurring pests. When used as a single application, spirotetramat and sulfoxaflor at the rate of 96 g (active ingredient, ha À1 ) provided variable control of CMB. Spirotetramat used in a double spray tactic (two sequential sprays, 14-15 days apart) without crop oil provided ≥80% control of adult CMB while the addition of oil (5% v/v) increased control to ≥90%. Clothianidin synergised the spirotetramat + oil combination and was identified as a potentially useful tank mix option for use in situations where a quick knockdown of high density and/or large infestation of CMB is required, or to treat high risk infestations in squaring or younger cotton when the abundance of beneficial insects is typically low. Sulfoxaflor used in a double spray tactic provided ≥90% control of adult CMB. The addition of Pulse® penetrant (0.5% v/v) to both options improved overall efficacy. Addition of crop oil to sulfoxaflor did not yield any tangible benefits. Spirotetramat and buprofezin were identified as important tools in managing situations where whitefly (Bemisia tabaci) is the primary pest management target, but CMB is also present in the crop. Buprofezin was effective on early instar mealybugs; this makes it an option for arresting CMB population growth while allowing the beneficial insect populations to increase. Sulfoxaflor was shown to be a useful option in situations where CMB is present along with key pests such as mirids (Creontiades spp.). Mealybugs are typically well controlled by naturally occurring beneficial insects without the need for insecticide use. Chemical insecticides for CMB control should be considered only as a last resort and deployed within the bounds of an IPM strategy.

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Insecticidal treatment options based on putative integrated pest management (IPM) compatible active ingredients spirotetramat, sulfoxaflor and buprofezin were evaluated for efficacy against first and second instar (small) and large (third instar and adult) cotton mealybugs, Phenacoccus solenopsis. Four field evaluations were conducted at the Department of Agriculture and Fisheries (Queensland) research station facilities at Kingaroy (KRS) and Emerald (ERS) in 2016 and 2017. Two 'insecticide evaluations' included treatment options with different rates of active ingredients and adjuvants, aimed at validating efficacy results obtained in previous glasshouse evaluations. The other two 'IPM evaluations' were designed to test the compatibility of selected insecticidal active ingredients with naturally occurring beneficial arthropods through differential exclusion by means of large field cages configured to be either partially open or fully closed to regulate access. Spirotetramat gave consistent and commercially acceptable (≥80%) control of large and small mealybugs at the highest rate of 96 g in these insecticide evaluations. The addition of crop oil to spirotetramat as a tank mix partner significantly enhanced efficacy, as documented previously in glasshouse evaluations. Sulfoxaflor provided equivalent control of large and small mealybugs but only at the ERS site. The overall control efficacy of buprofezin was equivalent to spirotetramat and sulfoxaflor at the ERS site but inferior to both at the KRS site. In the IPM evaluations, the abundance of predatory arthropods and their potential contribution to overall mortality was generally low. Parasitism contributed significantly to overall mortality among treatments over time and was independent of cage status (closed or open). Large mealybugs were equitably distributed between the upper (terminal) and lower sections of the cotton plant canopy in both ERS evaluations whereas in the KRS evaluations the distribution was biased towards the lower section. The importance of pest distribution within the crop canopy in the context of insecticide efficacy is discussed. The results of this study confirm the importance of spirotetramat, sulfoxaflor and buprofezin as key insecticidal platforms that will give growers and crop managers the flexibility and confidence to implement sustainable, multi-pest IPM strategies in Australian cotton.