Invasive plant-invasive insect interactions: Giant reed invasions as suitable refuge for cattle fever ticks (Acari: Ixodidae)

Though eradicated from the US for the past half century, reemergence of populations of southern cattle tick, Rhipicephalus (Boophilus) microplus, and cattle-fever tick, R. (B). annulatus which transmit the blood parasites that cause lethal cattle disease, is of major concern. Given that the key management area of Rhipicephalus ticks in south Texas overlap with the densest infestations of invasive giant reed (Arundo donax L.) in the US, we determine whether giant reed invasions are positively or negatively associated with survival of ticks. We look at tick survivorship and reproduction in three common riparian habitats: native forests, arundo stands, and pastures of exotic buffelgrass. Engorged females in the three habitats were likely to lay eggs and larger masses in arundo and native forests when compared to ticks in buffelgrass where daily temperatures were higher. Average high temperatures predicted the proportion of egg laying ticks (b=-15.81, t(8)=25.74, p < .001) and size of egg masses (b=-0.00916, t(8)=9.41, p < 0.001). The proportion of ticks that laid eggs and resulting mass were correlated, suggesting in areas with favorable climates (arundo stands and native forests) a greater percentage of ticks lay eggs and the mass is larger. However, results from pitfall traps revealed the relatively high abundance of potential ground dwelling predators (ants and spiders) and overall higher diversity of insects in native forests suggest arundo stands would be more suitable for cattle fever ticks given biotic and abiotic factors.