Ohio State University
Universidad del Valle de Guatemala (Guatemala); Ciba-Bunting, Oxnard, California (US)
Guillermo E Sanchez (Guatemala); Roger N. Williams (US)
In Guatemala, two-spotted mites (Tetranychus sp.) represent the main arthropod pest affecting raspberries. Mite infestations are difficult to control due to the lack of satisfactory control measures. Releases of the predatory mite Phytoseiulus persimilis, at three different rates (30,000; 60,000 and 120,000 individuals/ha) were done in a raspberry plantation located in the central highlands of Guatemala (Parramos, Chimaltenango). The effectiveness of these P. persimilis densities was compared to an untreated plot (no release of beneficial mites). Treatments were replicated five times in a randomized complete block design. Tetranychus counts were done 4 times, at intervals of 15-20 days, the first being 1 day before the release of the biocontrol agent.
No significant differences were found in Tetranychus populations between the different treatments. The lack of success, in contrast to the results obtained in 1997, may be attributed to the lack of proper crop management given to the raspberry fields, caused by the market restrictions restraining Guatemalan raspberry exports from May to August 1998.