Neochrysocharis okazakii(Hymenoptera: Eulophidae) as a Major Parasitoid Wasp of Stone Leek Leaf MinerLiriomyza chinensis(Diptera: Agromyzidae) in Central Vietnam

Abstract

Liriomyza chinensisis a major pest of Welsh onionAllium fistulosumin Asia but little is known about the abundance of its natural enemies. A field survey was made to explore the major parasitoids ofL. chinensisleaf miner in central Vietnam. An eulophid parasitoid,Neochrysocharis okazakii,comprised more than 95% of parasitoids reared from leaf miner larvae collected in the onion field and 98.3% of leaf miner parasitoids found during searches of onion plants. The mean number of femaleN. okazakiion plants was greater in onion fields with a higher density ofL. chinensis, and, during searches, a greater proportion ofN. okazakiiwas found on onion with moreL. chinensismines, suggesting density-dependent parasitoid aggregation. Melanized dead larvae ofL. chinensiswere more frequently found in onion fields with more parasitoids, demonstrating that melanized leaf miners are a good indicator of parasitoid activity. Mean instant rate of host encounter byN. okazakiiin the field was estimated at 0.077, and the likelihood of a parasitoid finding a host increased with host density. Taken together, these results show thatN. okazakiiis the major parasitoid ofL. chinensis. Usefulness of this parasitoid in stone leek leaf miner management is discussed.