Lygodium microphyllum, the Old World climbing fern, native to the Old World wet tropics and subtropics, is classified as a Category I invasive species and has infested over 107,000 acres of moist habitats in southern Florida. Herbicidal and mechanical controls to limit it’s growth and subsequent damage are expensive, have limited effectiveness, and cause considerable damage to non-target plants.
Floracarus sp. (Acarina: Eriophyidae) may be a candidate for biological control of the fern in Florida. This mite is the most widespread arthropod associated with the Old World climbing fern and is active year round. Mature females prefer the new sterile pinnae for oviposition. Newly formed leaf curling revealed up to five adults inside, although a single gravid female is able to cause the development of the deformation (curled-leaves) for itself and later for all its progeny. The leaf curls over downward and inward rolling on itself two-three times and eventually dries and falls at which time adults move to another young pinnae to feed and initiate new curls. Feeding by the adults and immatures leads to leaf necrosis and premature defoliation gradually debilitating the plant.
Ultrastructural characteristics of the epidermal layer of the fern as well as the ultrastructure of the mite mouthparts will be reported. Of particular interest are the structure and length of the mite stylets in relationship to the fern epidermal wall characteristics. The ultrastructural damage begins in the abaxial layer of the epidermis and spreads throughout the mesophyll tissue.
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