Steps Taken to Mitigate the Threats of Maximum Residue Limits (MRL) of Pesticides in Rice and Protecting Guyana Rice Exports Markets: Present and Future Prospects

Abstract

Governments of many countries are setting Maximum Residue Levels (MRLs) for food and feed being imported. To safeguard the threat of MRLs to rice exported from Guyana, the GRDB embarked on several research projects with the view to reduce MRLs and manage ‘Paddy bug’ (Oebalus poecilus (Dallas)). Studies included viz. identification of biological control agents; screening advance germplasm for tolerance; evaluation of bio-pesticides and synthetic molecules with higher MRLs; pesticide residue studies-growth stages, cut-off points and MRLs between paddy vs. cargo rice. Results from the bioagent survey found relatively low populations of predators such as damsel fly, lady bird beetle, spider, and dragon fly in Regions #2, #3, #4, #5, and #6. Also, there were isolated cases of parasitoids, viz. Telenomus podisi and Beskia aelops at very low levels. Results from the tolerance screening revealed that entry FG-18-222 recorded the highest percentage of damage and high incidence of paddy bugs (PB), while significantly (p < 0.05) lowest damage was recorded in FG-15-35 (2.13%), G17-109 (3.93%), followed by G-14-10 (4.10%) in 2022. These entries appeared to be the least preferred to PB due to the high presence and relatively low percentage of grain damage. However, all 12 entries were found to be susceptible to paddy bug lighting and feeding. Likewise, Bio-insecticide Boom (MRLs 3.0 mg/kg) was evaluated against PB and 162 ml/ac. was the most effective rate. In a separate experiment, Malathion (MRLs of 8.0 mg/kg) at 12–18 ml/ac. was most effective in controlling PB population compared to untreated control. There were no significant differences between these two treatments and the Pronto (Imidacloprid) check. The results from the pesticide residue analysis viz. Imidacloprid and Thiamethoxam, showed that systemic A.I. can only be applied once in a rice growing season for PB control no later than 67 DAS. Additionally, results comparing detected MRLs between paddy grains versus shelled rice grains revealed >84.41% reduction in the detected MRLs for these systemic A.I. Further research work is recommended in this MS to be undertaken to better understand the PB and mitigate the threat of MRLs with the view of developing an IPM approach to manage PB at the same time protect Guyana rice export markets.