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 pestmanagement, 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 degrees C, the optimum temperature for flight as 25 degrees C and the upper flight threshold as 28 degrees 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 degrees 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.