Acaricidal effects and residues of profenofos and abamectin on the nut-infesting eriophyid mite, Aceria guerreronis Keifer (Acari: Prostigmata) on coconut.

摘要

In recent years the coconut in south India has been under severe threat from invasion by the eriophyid mite Aceria guerreronis Keifer (Acari: Prostigmata). Since 1998 it has attained a major pest status, particularly in three peninsular states of India, namely, Kerala, Karnataka and Tamil Nadu, and has spread northwards. Severe damage can lead to premature nut drop or extreme reduction in the size of nuts. We evaluated abamectin 1.8 EC (2.5, 5.0 and 7.5 ml), profenofos 50 EC (10, 15 and 20 ml) and monocrotophos 36 SL (15 ml) and applied to roots as aqueous solutions for their efficacy in controlling the mite. Root feeding with abamectin 7.5 ml+7.5 ml water and abamectin 5 ml+5 ml water resulted in moderate reductions of 58.84% and 51.44% of the mite population, respectively, and also produced bunches with least damage. The other treatments caused less than 50% reduction in the mite population. No detectable residues were noted for abamectin, whereas in the profenofos treatments residues were detected from 3 to 30 days in the coconut kernel and water in the 15 ml+15 ml water and 20 ml+20 ml water treatments after the second round of root feeding. The kernel samples had 0.014 and 0.021 micro g/g residues in the 15 and 20 ml treatments, respectively, whereas the residues were below detectable levels in water samples from day 45 after treatment. Hence, a waiting period of 45 days after root feeding is recommended before harvesting of tender coconuts and matured nuts.