BARRIER SPRAY TREATMENT WITH DIFLUBENZURON (ULV) AGAINST GREGARIOUS HOPPER BANDS OF THE MOROCCAN LOCUST DOCIOSTAURUS-MAROCCANUS (THUNBERG) (ORTHOPTERA, ACRIDIDAE) IN NE MOROCCO

Barrier treatments of diflubenzuron were applied in advance of mobile hopper bands of Dociostaurus maroccanus in grassland and cereal crops in Morocco. Bands entering wheat and barley crops (69-120 tillers m(-2); ear emergence stage), treated with diflubenzuron barriers (50 m deep) at a rate of 60 g a.i. ha(-1) within the treated area, experienced high levels of mortality at subsequent moults. There was a significant positive correlation between the proportion of the treated groups moulting and the level of population decline; this did not occur in the control bands. Bands entering barrier treatments in cereals also demonstrated reduced rates of displacement compared with a control band and, although hopper densities remained similar to the control, the band area declined relative to the untreated population. A treatment on low-density annual grassland was less effective, possibly as a result of low vegetation density.