Use of an inexpensive technique to compare systemic insecticides applied through drip irrigation systems in citrus.

摘要

Throughout the world, farmers are increasingly adopting the use of drip irrigation. As the quality and automation of these irrigation systems improves, the feasibility of using them to apply plant protection products, growth regulators and nutrients also increases. An inexpensive means of evaluating such systemic products in a randomized block layout is described and its use demonstrated in evaluating drip applications of imidacloprid, methamidophos, monocrotophos, acephate and dimethoate in a 'Marsh' grapefruit (Citrus paradisi Macf.) orchard in Swaziland. Efficacy was tested against Toxoptera citricida (Kirkaldy), Scirtothrips aurantii Faure and various species of mealybug (Pseudococcidae). Imidacloprid and dimethoate proved the most promising systemic treatments, but usage of dimethoate on citrus trees with fruit destined for export to the European Union has now been restricted by the recent lowering of maximum residue limits for dimethoate. The sequential application of imidacloprid (2.1 g [AI] per tree) via drip followed by a petal-fall spray of spinosad (0.0072% [AI]) plus horticultural mineral oil (0.3%) was more effective against S. aurantii, but less efficacious against mealybugs, than dimethoate (36 g [AI] per tree) via drip followed by spinosad plus oil (dosages as above) applied at the same times..