Diamondback Moth (Lepidoptera: Plutellidae) Contamination of Cabbage Transplants and the Potential for Insecticide Resistance Problems

Abstract

Samples collected from 1989 to 1992 document that the diamondback moth, Plutella xylostella (L.) was introduced into New York in early spring on cabbage, Brassica oleracea capitata (L.), transplants grown in the southern United States. During 1989, transplant shipments from five transplant companies in Florida, Georgia and Maryland were sampled for P. xylostella. In 1989, average seasonal infestations per transplant company ranged from 1.3 to 3.5 P. xylostella per 100 transplants. During June, when the majority of transplants arrived in New York, P. xylostella infestations were as high as 12.8 insects per 100 transplants on an individual shipment. Infestations by cabbage looper, Trichoplusia ni (Hübner), imported cabbageworm, Artogeia (=Pieris) rapae (L.), and cabbage webworm, Hellula rogatalis (Hulst), on an individual shipment were as high as 19.7 insects per 100 transplants. Compared with a standard susceptible field population, the P. xylostella which were collected from transplants demonstrated moderate to high (> than 100-fold in one case) levels of resistance to permethrin or methomyl. In 1990, average seasonal infestations per transplant company varied from 0.3 to 12.0 P. xylostella per 100 plants, but an individual shipment from Florida had 30.4 P. xylostella per 100 transplants. A population of P. xylostella collected in 1990 from Florida transplants had >200-fold resistance to methomyl. Despite intensive treatments, a New York grower who used the transplants with high contamination of resistant P. xylostella was unable to achieve acceptable control in his field. Samples collected from 1989 to 1992 from a transplant grower in Maryland indicate that better management in the field can reduce contamination levels to < 0.5%. The introduction of P. xylostella, especially those resistant to insecticides, on transplants poses a serious threat to cabbage growers and interregional management strategies should be adopted.

The effects of local selection versus dispersal on insecticide resistance patterns: longitudinal evidence from diamondback moth (Plutella xylostella(Lepidoptera: Plutellidae)) in Australia evolving resistance to pyrethroids

“…Locations either had persistently high or low resistance levels over several years, likely to be related to continued selection for resistance because of pyrethroid applications. Although P. xylostella may be transported on vegetable transplants leading to resistance problems in other localities (Shelton et al, 1996), no obvious patterns attributable to this phenomenon were observed in this study, though the origin of vegetable seedlings at particular locations was not traced in detail.…”

Population dynamics of Plutella xylostella (Lep., Yponomeutidae) and its parasitoids in the region of Brasilia

“…This can be easily explained for P. xylostella as it is an excellent migrator ( Chu , 1986) but is more difficult to explain for the guild. One would have to suppose a massive introduction of these species during the transport of cabbage plants ( Shelton et al., 1996) or possibly that they were already present on other hosts. This appears to be the case for T. diatreae which originally also attacked other Lepidoptera, principally Noctuidae but is a pupal parasitoid of P. xylostella in Jamaica ( Alam , 1992).…”

Low mtDNA diversity among widespread Australian diamondback moth Plutella xylostella (L.) suggests isolation and a founder effect

“…The sources of these outbreaks have not been identified, but reports, especially from the northern hemisphere, indicate that DBM is a migratory species and periodically disperses over long distances (Chu, 1986;Talekar & Shelton, 1993). Also, larvae can be brought into a cropping region on imported vegetables (Voice & Chapman, 2000) or contaminated seedlings (Shelton et al, 1996). Studies of population-genetic structure have potential to help in determining gene flow patterns, and hence dispersal and movement patterns, of DBM across Australia and in other regions of the world.…”