Role of insects in the dispersal of Claviceps purpurea, a fungal pathogen causing ergot disease of grass seed crops

The fungal pathogen, Claviceps pupurea (Fr.:Fr.) Tul. is known to cause ergot disease of grass seed crops in Columbia Basin region of Washington and Oregon. This disease has been particularly difficult to manage. The fungus targets the unfertilized flowers and replaces the seed content with fungal mycelia. The infected ovaries then produce conidia carried in a sugary exudate known as honey dew which is believed to increase insect feeding and thus may facilitate disease spread. Although the association of insects in grass seed crops with ergot causing fungi has been investigated, limited information exists on the insect population dynamics and their dispersal ability. Therefore, we sought to determine if an association existed between insect abundance and ergot incidence in perennial ryegrass (PRG) (Lolium perenne L.) and Kentucky bluegrass (KBG) (Poa pratensis L.) fields. Four commercial fields of PRG and KBG were surveyed weekly to monitor numbers and collect insect during May to July, 2014. The sampling techniques included universal black light traps, delta traps, yellow sticky cards, and modified sweep netting to avoid any direct contamination of honey dew during collection. Insects were counted and stored individually in separate containers until their examination for the presence of fungal spores using molecular techniques. Understanding the importance of insects for spreading ergot may aid in the management of this disease.