Environmental and biological drivers of flight initiation in a sporadic pest, Rutherglen bug, Nysius vinitor Bergroth (Hemiptera: Orsillidae)

Abstract

Flight initiation is fundamental to insect dispersal. Insights into the meteorological and environmental drivers of flight initiation, and their relative importance, can therefore help determine the conditions under which mass dispersal events may occur. In relation to insect pest management, the ability to anticipate such events would allow us to predict mass colonisation of crops and better manage outbreaks of an insect pest. This study insects aims to better predict flight initiation of Rutherglen bug, Nysius vinitor, and thus crop outbreaks originating from over-winter weed hosts. We examined the influence of temperature in combination with sex and the availability of food and water, under controlled environment conditions inside a flight chamber. Most of the variation in flight initiation was explained by temperature. We found that warm temperatures are required for flight initiation: the lower flight threshold was determined as 21°C, the optimum temperature for flight as 25°C and the upper flight threshold as 28°C, fitting a quadratic distribution. However, additional data shows that such thresholds are not limiting: when N. vinitor is under extreme heat stress (35-40°C) for a short period, they have a very high propensity to take-off. The rate of flight initiation was fastest within the first 5 h in both males and females for all tested temperatures. A lack of food and water resulted in a faster take-off rate of males, but had no effect on female flight initiation. Application of our analysis to temperature data in New South Wales (NSW) and Queensland (Qld), Australia, indicates that flight initiation in N. vinitor is likely to be highly seasonal, with very little flight activity expected in winter in eastern Australia. We found a longer suitable flight period and a greater number of suitable flight days per month in Qld compared to NSW. Such estimates could be used to inform regional pest arrival forecasts, integrated pest management decisions and the development of dispersal simulation models for this pest.

A native with a taste for the exotic: weeds and pasture provide year‐round habitat for Nysius vinitor (Hemiptera: Orsillidae) across Australia, with implications for area‐wide management

“…). The wide host range allows N. vinitor to move between non‐crop and crop hosts in times of environmental stress (Kehat and Wyndham ; Moradi‐Vajargah and Parry ). This allows N. vinitor populations to persist under less favourable conditions, build‐up their population and (re‐)colonise crops when conditions are more favourable.…”

“…Chemical pest management options to control N. vinitor are currently limited to older broad spectrum insecticides, such as pyrethroids and dimethoate, which are only moderately effective due to movement propensity and avoidance behaviours (Moradi‐Vajargah and Parry ) and hold the potential for pest resurgence when their residual activity wears off. As a consequence, crops like sunflower and sorghum with an extended period of susceptibility may require repeated applications, and the use of these chemicals is associated with an increased risk of Helicoverpa sp., mites and silverleaf whitefly populations surging or developing resistance.…”