Eriophyid mite Floracarus perrepae readily colonizes recovering invasive vine Lygodium microphyllum following herbicide treatment

Abstract

Lygodium microphyllum (Cav.) R. Br. (Schizaeales: Lygodiaceae) is among the most damaging invasive plant species in Florida, USA. Following mechanical and herbicide treatment, the plant typically recovers to pre-treatment levels within 1–2 years through regrowth from the adult rhizome and recruitment of new sporelings. A classical biocontrol agent, the gall-inducing mite Floracarus perrepae Knihinicki & Boczek (Acariformes: Eriophyidae), could attack recovering L. microphyllum, thereby reducing the need for repeated treatments. Here, we investigated natural F. perrepae colonization of recovering L. microphyllum following treatment using two field experiments. First, we monitored F. perrepae colonization on adult regrowth and sporelings on tree islands that were clipped and treated with herbicide (glyphosate or triclopyr). At 24 months post-treatment, mite galls were most abundant on glyphosate treated islands where > 50% of adult rachises and > 80% of sporelings exhibited galls and were rare on untreated islands. Second, we investigated the separate effects of clipping and herbicide (triclopyr) treatment on F. perrepae colonization of regrowth within small-scale plots at four heavily invaded sites. Galls were most prevalent following cutting and least prevalent following herbicide seven months post-treatment, but, on a per pinna (i.e., leaflet) basis, were equivalent across treatments. Taken together, we report that both L. microphyllum regrowth and especially sporelings were highly susceptible to colonization by F. perrepae. Our findings suggest that biological control of L. microphyllum is compatible with herbicide treatment, and future research is needed to determine how best to integrate these management tactics.