A capacity to accurately assess economically important insects and their impact on crop physiology is pivotal to making informed and cost-effective decisions within an Integrated Pest Management (IPM) framework. The use of transgenic cotton provides a strong platform for IPM in the management of Helicoverpa spp. However, sucking pests such as Creontiades dilutus (green mirid) and Nezara viridula (green vegetable bug) are not controlled by the Bt toxin produced by transgenic cotton. Traditional sampling techniques can underestimate abundance of green mirid and green vegetable bug populations in cropping areas because these pests are easily dispersed and their distribution is often not uniform in cotton fields. Therefore, there is an urgent need to develop an effective surveillance system to measure peak activity of these pests throughout the growing season and to provide a predictive tool for identifying quantitative shifts in population abundance that would optimise the timing of control measures.

The Zappa trap was previously tested in proof-of-concept trials over a three year period from 2015 to 2018. Results of these trials demonstrated the potential of the Zappa trap as a sentinel tool for providing growers with an early warning of pest presence, particularly green mirids and green vegetable bugs, which are otherwise difficult to quantify under field conditions. The Zappa trap could also have a direct pest management application as an “attract and kill” strategy, potentially offering growers an alternative method to reduce pest numbers while mitigating risk to non-target species and enhancing the IPM potential in cotton.

The aim of this one year project was to further test the potential of the Zappa trap in field trials located in different cotton growing regions and under intensive sampling regimes. The results provided additional evidence that Zappa trap sampling could be a useful biological indicator for predicting the timing of mirid nymph activity in cotton because temporal synchrony was consistently observed between adult mirids recorded from Zappa trap and total mirid numbers samples recorded during in-field insect checks. Notwithstanding the possibility that Zappa trap sampling could be confounded by environmental factors such as the speed and direction of prevailing winds, the information could nevertheless provide an early warning for the presence of populations in the vicinity of cotton fields and heighten grower awareness to the need for vigilant assessment of pest abundance to optimise the timing of spray applications.

The study of trap placement on the distribution of mirids within cotton indicated that mirid nymph abundance may be influenced by distance from the trap location. Results from the assessment of crop damage generally support the insect abundance and distribution data and there was a trend toward higher levels of insect damage to bolls and lower yield potential at increasing distances away from traps, suggesting that the placement of traps in strategic locations around cotton fields could have a positive influence on yield outcome.

The predictive capability of the Zappa trap could provide the opportunity to manage populations in a timely manner and minimise the damage to fruiting structures of plants while optimising the cost of effectively and sustainably managing green mirids and green vegetable bugs on cotton. An additional benefit could be an increased understanding by growers of pest phenology and behaviour of these problematic species which could reduce reliance on chemical control measures and reduce the risk of flaring end-of season-pests in cotton such as silver leaf whitefly.