Spatial distribution of 17-year periodical cicada (Hemiptera: Cicadidae) exuviae and oviposition injury in Mid-Atlantic, USA Apple orchards and implications for management

Abstract

Tree fruit orchards in some Mid-Atlantic states are within the geographic range of 17-year periodical cicada Brood X, Magicicada septendecim (L.) and M. cassini (Fisher) (Hemiptera: Cicadidae), and can be badly affected by injury from its oviposition in branches. Several applications of broad-spectrum insecticides, such as pyrethroids, are needed to mitigate this injury, but can incite secondary pest outbreaks by impacting natural enemy populations. The spatial distribution of cicada exuviae and oviposition injury in orchards have not been examined in relation to edge effects or the effect of different adjoining habitats, from which cicadas can move into orchards. Addressing these knowledge gaps may reveal the potential for spatially precise insecticide applications targeting cicadas, thereby mitigating the effects of spraying entire orchard blocks. In 2021, the distribution of Brood X cicada exuviae (a proxy for oviposition during its emergence 17-years previously) and oviposition injury was measured using tree transects in commercial apple orchards in Virginia and West Virginia, USA. All orchards had woods and non-woods habitats along opposite borders, and depending on their age, were or were not exposed to cicadas previously. Orchard edges facing and not facing woodlands were vulnerable to the effects from cicada. Overall, there was a tendency for somewhat higher numbers of exuviae and oviposition sites in orchard border rows facing woods, however both variables were recorded in considerable numbers in the orchard interior on edges facing and not facing woods. Results are discussed in relation to their implications for cicada management in fruit orchards.