Potential of synthetic sex pheromone blend for mating disruption of the swede midge, Contarinia nasturtii.

The potential for pheromone-based mating disruption of the Brassica pest Contarinia nasturtii was tested, both in small-scale plots with Brussels sprouts and in commercial-scale fields with either broccoli or cauliflower. Experiments in the small-scale plots used laboratory-reared insects released into a previously uninfested area, whereas large-scale experiments used a high natural population of C. nasturtii. Effectiveness of mating disruption was evaluated by the reduction of male captures in pheromone traps, and by reduction of crop damage caused by C. nasturtii. Dental cotton rolls (small-scale experiment) and polyethylene caps (large-scale experiment), containing 50 µg (2S, 9S)-diacetoxyundecane, 100 µg (2S,10S)-diacetoxyundecane, and 1 µg (2S)-acetoxyundecane, spaced 2 m apart, served as dispensers in the test plots. In both experiments, mean catches of C. nasturtii males in pheromone traps were reduced to near zero in treated plots, with control plots averaging 71 males/trap. In the large-scale experiments, no males were caught in pheromone traps over a period of 41 days after mating disruption was applied; one male was caught from days 42-60. In the small-scale trials, crop damage was reduced by 59 %, compared to the untreated control plot. In the large-scale experiments, damage was reduced on average by 91 %. This study shows successful field application of the mating disruption technique for control of a member of the dipteran family Cecidomyiidae, and demonstrates that pheromone-based mating disruption has potential for management of C. nasturtii populations.

Detection of Contarinia nasturtii (Diptera: Cecidomyiidae) in New York, a new pest of cruciferous plants in the United States.

The midge Contarinia nasturtii Kieffer (Diptera: Cecidomyiidae) was first confirmed in North America in Ontario, Canada, in 2000. The insect is now distributed throughout many counties in the provinces of Ontario and Québec. Nearly 1,200 farms in the northeastern United States that grow cruciferous vegetables are at risk for C. nasturtii infestation if this insect were to spread to that region. Over a period of 3 yr (2002-2004), approximately 3,000 ha of crops on 94 farms in western New York State was scouted for C. nasturtii, but none were found. In 2004, 42 experimental pheromone traps were placed in fields of cruciferous vegetables in eight counties. C. nasturtii males were captured at low levels (1-50 per trap / 8 wk) on four farms in Niagara County, but not at any other site. C. nasturtii larvae were found in plant tissue at one of the four farms. Insect specimens were identified by morphological methods, molecular methods, or both. This is the first confirmation of C. nasturtii in the United States, which we believe was made possible by the combined use of pheromone traps, morphological characters of trapped adults, and molecular methods. The early detection in New York presents an opportunity to implement measures to limit the spread and establishment of C. nasturtii across the state and into other regions of the United States.

Optimisation of the pheromone blend of the swede midge, Contarinia nasturtii, for monitoring.

BACKGROUND: The swede midge, Contarinia nasturtii Kieffer, is a serious pest in crucifers. Its pheromone is a blend of (2S,9S)-diacetoxyundecane, (2S,10S)-diacetoxyundecane and (2S)-acetoxyundecane. The pheromone is used in monitoring traps, and this study examines possible ways to optimise the traps. RESULTS: Two dispenser types were compared: polyethylene dispensers and cotton dispensers. Polyethylene dispensers attracted male C. nasturtii for more than 6 weeks, whereas cotton dispensers were attractive for only 2 weeks. All three pheromone components were important for attraction of male midges in the field. The importance of the stereoisomeric compositions of the pheromone compounds was also tested-both in the wind tunnel and in the field. In the case of 2,9-diacetoxyundecane and 2-acetoxyundecane, the non-natural stereoisomers did not inhibit male C. nasturtii attraction, whereas one or both of the stereoisomers of 2,10-diacetoxyundecane did. CONCLUSION: Pheromone traps with the synthetic pheromone in a 1:2:0.02 ratio emitted from PE dispensers were highly effective and long lasting. As the mixture of stereoisomers of 2,10-diacetoxyundecane strongly inhibited attraction of male C. nasturtii while those of 2,9-diacetoxyundecane and 2-acetoxyundecane did not have any inhibitory effect, it is possible to produce traps that are effective and long lasting but cheaper to produce and maintain.

Identification of the sex pheromone of the swede midge, Contarinia nasturtii.

Coupled gas chromatographic-electroantennographic detection analyses of ovipositor extracts of calling Contarinia nasturtii females revealed two compounds that elicited responses from antennae of male midges. Using synthetic reference samples, these components were identified by gas chromatography mass spectrometry and enantioselective GC as (2S,9S)-diacetoxyundecane and (2S,10S)-diacetoxyundecane. In addition, trace amounts of 2-acetoxyundecane were found in ovipositor extracts, and the (S)-enantiomer was synthesized. When tested in the wind tunnel, a blend of 5 ng (2S,9S)-diacetoxyundecane and 10 ng (2S,10S)-diacetoxyundecane (mimicking the ratio found in the extracts) did not attract any of the males tested, but when 0.1 ng (S)-2-acetoxyundecane was added to the blend, 86.8% of the males were attracted to the bait. Three-component blends with lower or higher relative concentrations than 1% of (S)-2-acetoxyundecane [relative to (2S,10S)-diacetoxyundecane] were less attractive. In a field trapping experiment with released laboratory-reared C. nasturtii adults, traps baited with 500:1000:10 ng of (2S,9S)-diacetoxyundecane/(2S,10S)-diacetoxyundecane/(S)-2-acetoxyundecane applied to rubber septa or dental cotton rolls were tested. Traps without dispensers were used as controls. All three treatments were tested at 20 and 50 cm above ground. The estimated recapture rate was 30-50%, and 81.9% of the recaptured males were caught in traps positioned at 20 cm above ground, and 88.4% in traps with dental cotton rolls as dispensers.