Oral presentation

 

Influence of Helicosporidium spp. Infection on Development and Survival of Three Noctuid Species

 

Verena-Ulrike Blaeske and Drion G. Boucias

Department of Entomology and Nematology, University of Florida, Gainesville, FL 32611

 

A Helicosporidium spp. (Chlorophyta: Trebouxiophyceae) isolate, recently purified from an aquatic weevil, Cyrobagus salviniae (Coleoptera: Curculionidae), was capable of infecting and reproducing in three heterologous hosts, Helicoverpa zea, Spodoptera exigua, and Trichoplusia ni (Lepidoptera: Noctuidae). Regardless of host species, oral treatment of third instars with Helicosporidium cysts resulted in about 50% infection of the challenged larvae. The sex ratio did not differ between infected and control groups, suggesting the existence of a natural, non-sex related resistance to the disease. Mating experiments with resistant individuals will enable us to follow this hypothesis in subsequent infection trials with the F1 generation. Injection of Helicosporidium spp. into the hemocoels of late instars resulted in >95% infection, suggesting that the resistance is related to the ingestion of the pathogen and therefore affiliated with midgut mediated barriers. Interestingly, the pathogen’s development was not interrupted by metamorphosis nor did the infection necessarily interrupt the insects’ development. When treated as early instars, 50-90% of the infected larvae formed pupa, of which 20-30% emerged as adults. However, a high proportion of the infected adults (62-86%) had malformed wings and longevity was reduced compared with healthy adults.