Mulching with grass-clippings in cauliflower: Effects on yield and brassica root flies (Delia spp)

The effects of mulching with organic materials on yield and damage by brassica root maggots (Delia floralis and D. radicum) in cauliflower, were studied in field experiments for 3 years. Mulching with grass-clippings consistently resulted in increased yield and reduced damage by root maggots, as measured by wilting symptoms and root damage. During one of these years, the effects of mulching with grass-clippings on root fly population dynamics was also studied. Mulching did not reduce egg-laying but resulted in increased egg-predation. The number of D. floralis pupae per plant was not reduced by mulching, probably because of higher larval mortality owing to competition in unmulched plots. Mulching decreased the rate of parasitization by Aleochara bilineata (Staphylinidae), resulting in a higher number of healthy pupae per plant in grass-mulched plots, and these healthy pupae were heavier. All these effects were most pronounced when the mulch material completely covered the ground, even close to the stems of the plants.