Cabbage root fly control using non-organophosphorus insecticides.

The need to find non-organophosphorus insecticides to control the cabbage root fly has never been so urgent. Of the six non-OP insecticides tested, fipronil was the most effective but spinosad, diflubenzuron and cyromazine also showed considerable promise. As expected, the transplant drenches (34 mg active ingredient (a.i./plant) were more effective than the module drenches (5 mg a.i./plant), which in turn were more effective than the film-coated seed treatments (0.001 mg a.i./plant), simply because of the different amounts of insecticide applied per plant. One remaining major problem is that, even if effective non-OP insecticides can be found, the manufacturers may still not support their insecticides being applied to minor crops such as field vegetables.

Carbofuran-degrading bacteria from previously treated field soils.

Laboratory incubation studies were made on soils collected from five field sites with different histories of treatment with carbofuran. All soils treated earlier with carbofuran degraded the compound more rapidly than untreated samples of the same soils. Reduced rates of degradation in the presence of chloramphenicol imply that soil bacteria are primarily responsible for the breakdown of carbofuran in these soils. Sixty-eight bacteria, capable of degrading carbofuran as the sole source of carbon and nitrogen, were isolated from liquid cultures of treated soils. The concentration of carbofuran in the liquid medium used for isolation and subsequent culture of carbofuran-degrading isolates appeared to affect the stability of their ability to degrade. Similar types of carbofuran-degrading bacteria were isolated from different soils and several different types were isolated from one soil. All carbofuran-degrading isolates were Gram-negative, aerobic rods which hydrolysed the insecticide to carbofuran phenol. They were separated into four groups on the basis of a limited number of phenotypic characters. There was a good correlation between the phenotype of carbofuran-degrading isolates and the stability of their ability to degrade. Fourteen isolates were placed in phenotypic group I and 13 of these did not degrade carbofuran after one subculture in liquid medium. Phenotypic groups II, III and IV consisted of 54 isolates in total (3, 46 and 5 isolates respectively) and 52 of these retained their ability to degrade carbofuran when subcultured.