Margarita Georgieva

Interactions between the introduced fungal pathogen Entomophaga maimaiga and indigenous tachinid parasitoids of gypsy moth Lymantria dispar in Bulgaria

Interactions between the gypsy moth, Lymantria dispar L. (Lepidoptera: Erebidae), pathogenic fungus Entomophaga maimaiga, and the tachinid parasitoid (Diptera: Tachinidae) complex in gypsy moth larvae were investigated in Bulgaria, where E. maimaiga was recently released as a biological control agent. Gypsy moth larvae were collected in oak stands where E. maimaiga was originally introduced (nine sites) and in sites where the pathogen has invaded by natural extension of the range (ten sites). In total, 4,375 host larvae were examined and 401 tachinid larvae emerged from parasitized hosts. Host mortality caused by tachinids varied from 0 to 48.5% among sites, with an overall average of 9.2%. Emerging adult tachinid parasitoids included 54 individuals belonging to six species: Compsilura concinnata, Exorista larvarum, Senometopia separata, Senometopia excisa, Drino incospiqua and Zenilia libatrix; the remaining parasitoids (86.5%) died in the pupal stage. E. maimaiga azygospores were observed on puparia surfaces, an indication that the gypsy moth host larvae were infected with the fungus. No azygospores were observed in parasitoid tissues. The high parasitoid mortality may be the result of the competition with E. maimaiga during development in the same host.

POTENTIAL OF ENTOMOPHAGA MAIMAIGA HUMBER, SHIMAZU AND SOPER (ENTOMOPHTHORALES) FOR SUPPRESSING LYMANTRIA DISPAR (LINNAEUS) OUTBREAKS IN BULGARIA

The Asian fungal entomopathogen Entomophaga maimaiga was first introduced in Bulgaria for biological control of gypsy moth, Lymantria dispar, in 1999 and the first epizootics in gypsy moth populations were observed in 2005. Six introductions of E. maimaiga in oak forests with heavy L. dispar infestations were conducted from 2008 to 2011 in different regions of the country, including Nova Zagora, Gorna Oryahovitsa, Popovo, Targovishte and Staro Oryahovo. As a result of these introductions, host density was decreased by 55.1–100% and the outbreaks were suppressed. After the introduction of the pathogen in Bulgaria, no microbiological or chemical control of L. dispar has been necessary and the last two gradations have been estimated to be 15–30% of the values in previous gradations.