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-cli ppings 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 ro ot fly population dynamics was also studied. Mulching did not reduce e gg-laying but resulted in increased egg-predation. The number of D. fl oralis pupae per plant was not reduced by mulching, probably because o f higher larval mortality owing to competition in unmulched plots. Mul ching decreased the rate of parasitization by Aleochara bilineata (Sta phylinidae), resulting in a higher number of healthy pupae per plant i n grass-mulched plots, and these healthy pupae were heavier. All these effects were most pronounced when the mulch material completely cover ed the ground, even close to the stems of the plants.