Control of onion thrips (Thrips tabaci) adults and eggs with phosphine
Onion thrips are a major pest of New Zealand onion and asparagus exports Onions are generally treated with methyl bromide if export shipments are contaminated with thrips Phosphine is a possible alternative fumigant for disinfestation particularly as it is less likely to have phytotoxic effects on onions than methyl bromide This research aimed to identify a short duration (23 day) phosphine treatment protocol using cylinderised phosphine that gave complete control of onion thrips adults and eggs without causing a decline in onion bulb quality Adults and egg life stages of onion thrips were treated with two concentrations of phosphine (700 and 1100 ppm) for either 48 or 72 h at a mean temperature of 20C Phosphine was applied directly to adult thrips that had been collected and held in jars as well as to infested onions None of the treated adults survived and none of the treated eggs hatched and survived after 48 h exposure to phosphine fumigation at a mean concentration of 706 ppm There were no visible signs of phytotoxicity following phosphine treatment It is recommended that this treatment regime is tested at a larger scale on stored onions infested with onion thrips