Current status of insect pests attacking green bunching onion in central and southern Vietnam

Green bunching onion (or Welsh onion) Allium fistulosum is traditionally an important vegetable in Vietnam. The present study was undertaken to survey the current status of insect pests on green bunching onion in the country. Survey was conducted in conventional fields in central and southern Vietnam. The most widespread pest was Stone leek leafminer Liriomyza chinensis, which occurred all lowland sites investigated except Da Lat, a highland site in central Vietnam. Although insecticides were intensively applied, the percentage of the occurrence in green onion fields was 100% in Bien Hoa, Hue, Huong An, and Quang Nam. In Dalat, L. huidobrensis instead was widely found in Allium fistulosum and A. cepa. Serious infestation by lepidopterans often occurred, and the main species was beet armyworm Spodoptera exigua, which was widely found in lowland areas. Infestation by S. exigua was heavier in summer than in spring. Damage by S. litura was observed in all localities. Helicoverpa armigra infested green bunching onion in Hue though it was rare. Thrips were rather a minor pest though it was abundant in Quang Nam. No pest aphids were confirmed. Taken together, management of leafminer and lepidopteran pests is crucial to stable production of marketable green bunching onions. Current problems associated with insect pest control in Vietnam are discussed, and the importance of IPM practices is emphasized. A series of color photographs of pests and the damage they can cause are presented to facilitate identification of the pest.