Surveillance for whiteflies on greenhouse roses and chrysanthemums in northern Tanzania

A specific monitoring survey for whiteflies was conducted in greenhouse-grown roses and chrysanthemums in northern Tanzania from October to December 2005. The survey objectives were to appraise the suitability of yellow traps made from locally available materials, to suggest action threshold levels, and to see if the area could be considered an Area of Low Pest Prevalence. Three farms, one growing roses and two growing chrysanthemums, were sampled in the major growing areas and Pest Management Units (PMUs) of 700 m² were formed from maps of the farmland. Twelve yellow traps were placed at intervals of 1.5 traps per PMU in the sampled farms and monitored weekly. Insects trapped included whiteflies, aphids, and occasionally fungus gnats and shore flies. The traps held insects during the period of exposure. Exposure of longer than five days in the field resulted in changes in the texture of the trap. Based on the results of these surveys, farmers are advised to take action when 1.5 whiteflies per trap in each PMU are recorded. The results show that Post Entry Plant Quarantine Inspectors could consider and recommend the area to be an Area of Low Pest Prevalence due to its tight pest management measures and routine inspections.