Efficacy of insecticide incorporated bags against major insect pests of stored paddy in Sri Lanka

Abstract

A study was conducted to evaluate the efficacy of an insecticide (deltamethrin) incorporated bags (Zerofly®) against the insect attacks during paddy storage under Sri Lankan conditions. The study was conducted at Institute of Post Harvest Technology (IPHT), Anuradhapura andat the warehouse of Paddy Marketing Board (PMB), Anuradhapura. Paddy sample in Zerofly® sacks were stacked at both locations and for controls, untreated polysack bags were used.Paddy samples that were collected before storage and at monthly intervals during the storage period were analysed for moisture content, weight loss due to insect damages, Thousand Grain Mass (TGM), germination percentage, Total Milling Yield (TMY) and Head Rice Yield (HRY). Data was analyzed using Analysis of Variance (ANOVA) by Statistical Analysis System (SAS). The moisture content of paddy grains fluctuated between 13.3 – 14.3% during storage period but any significant difference was not observed among bag types. The level of insect damages in control was increased with storage time while the initial level of insect damage of treated bags remained unchanged.The mass loss due to insect damagesof grains was significantly higher (p=0.05) in untreated bags than treated bags. The insect damage was reduced by 3.5-4.a% using Zerofly® bags during paddy storage. In addition, dead insect bodies were found onouter surface of the insecticide incorporated bags but no live or dead insects were found on untreated bag surface during storage. Mainly rice weevil (Sitophils oryza) and lesser grain borer (Rhysoperthadominica) were found in paddy samples of untreated bags and number of insects increased with time. The germination percentage of grains in untreated bags was significantly higher than to thecontrol. It was reduced from 93% to 60-64% and 93% to 82-83% in control and treated bags respectively.During the six months of storage, TGM did not show any significant difference (p=0.05) among different treatments. TMY and HRY resulted significantly (p=0.05) lower values of paddy stored in untreated bags than Zerofly® bags. Use of insecticide incorporated bags can reduce the loss of TMY and HRY of paddy during storage. The study revealed that insecticide treated bags are an appropriate packaging material to protect stored paddy from insect infestations under Sri Lankan conditions.