Pesticide Residues in Fruits and Vegetables

Chemical ecology of Himalayan eggplant variety's antixenosis: identification of geraniol as an oviposition deterrent against the eggplant shoot and fruit borer

Eggplant (Solanum melongena) suffers severe losses due to a multi-insecticide-resistant lepidopteran pest, shoot and fruit borer (SFB, Leucinodes orbonalis). Heavy and combinatorial application of pesticides for SFB control renders eggplant risky for human consumption. We observed that gravid SFB females do not oviposit on Himalayan eggplant variety RC-RL-22 (RL22). We hypothesized that RL22 contained an antixenosis factor. Females' behavior indicated that the RL22 cue they perceived was olfactory. To identify it, leaf volatile blends of seven eggplant varieties were profiled using solid phase microextraction and gas chromatography mass spectrometry. Seven RL22-specific compounds were detected in the plant headspace. In choice assays, oviposition deterrence efficacies of these candidate compounds were independently tested by their foliar application on SFB-susceptible varieties. Complementation of geraniol, which was exclusively found in RL22, reduced oviposition (> 90%). To validate geraniol's role in RL22's SFB-deterrence, we characterized RL22's geraniol synthase and silenced its gene in planta, using virus-induced gene silencing. Geraniol biosynthesis suppression rendered RL22 SFB-susceptible; foliar geraniol application on the geraniol synthase-silenced plants restored oviposition deterrence. We infer that geraniol is RL22's SFB oviposition deterrent. The use of natural compounds like geraniol, which influence the chemical ecology of oviposition, can reduce the load of hazardous synthetic larvicides.

Residue and soil dissipation kinetics of chloroacetanilide herbicides on rice (Oryzae sativa L.) and assessing the impact on soil microbial parameters and enzyme activity

The present investigation determines the persistence of herbicides like butachlor and pretilachlor in Indian soil, and their impact on soil biological properties including microbial biomass carbon (MBC), total microbial population numbers, and enzyme activities. Butachlor was degraded faster in autumn rice soil (t1/2 of 10-13 days) than in winter rice soil (half-life of 16-18 days). The t1/2 of pretilachlor in winter rice was 12-16 days. Regardless of the seasons under cultivation, no pesticide residue was detected in rice at harvest. Herbicides induced an initial decline (0-14th days after application) in MBC (averages of 332.7-478.4 g g-1 dry soil in autumn rice and 299.6-444.3 g g-1 dry soil in winter rice), microbial populations (averages of 6.4 cfu g-1 in autumn rice and 4.6 cfu g-1 in winter rice), and phosphatase (averages of 242.6-269.3 μg p-nitrophenol g-1 dry soil h-1 in autumn rice and 188.2-212.2 μg p-nitrophenol g-1 dry soil h-1 in winter rice). The application of herbicides favored dehydrogenase (averages of 123.1-156.7 g TPF g-1 dry soil in autumn and 126.7-151.1 g TPF g-1 dry soil in winter) and urease activities (averages of 279.0-340.4 g NH4 g-1 soil 2 h-1 in autumn and 226.7-296.5 g NH4 g-1 soil 2 h-1 in winter) in rice soil at 0-14th DAA. The study suggests that applications of butachlor and pretilachlor at the rates of 1000 g ha-1 and 750 g ha-1, respectively, to control the weeds in the transplanted rice fields do not have any negative impact on the harvested rice and associated soil environment.

Insight on Fruit Fly IPM Technology Uptake and Barriers to Scaling in Africa

Tephritid fruit flies are considered one of the world’s most notorious pests of horticultural crops, causing extensive direct and indirect damage. Over the past two decades, a comprehensive, integrated pest management (IPM) package for the management of a plethora of fruit fly pests, including Bactrocera dorsalis, B. latifrons, B. zonata, Ceratitis cosyra, C. rosa, C. fasciventris, C. quilici, C. capitata, Dacus spp. and Zeugodacus cucurbitae, has been developed, disseminated and promoted among horticultural growers in Africa. To estimate the numbers of beneficiaries reached by the fruit fly IPM technology and the barriers to technology uptake, we interviewed 290 experts in 30 African countries covering five regions of the continent, and the responses collected were represented as follows: Southern Africa (39.1%), Eastern Africa (31.6%), Western Africa (18.0%), Central Africa (9.0%) and Northern Africa (2.0%). Our results revealed that the use of fruit fly IPM technologies varied across the regions, with Eastern Africa and Western Africa the leading regions, with the highest IPM technology penetration. Field sanitation remains the most common practice for managing fruit flies, followed by protein bait spray, use of biopesticides, male annihilation technique and parasitoid releases. According to the survey, over 101 million people have benefited from the fruit fly IPM interventions in the countries surveyed representing only 19.1% of the estimated beneficiaries. The region that benefitted the most was Eastern Africa (50.2 million), followed by Central and Western Africa (11.7 to 17.7 million), and Southern and Northern Africa had the fewest beneficiaries (10.4 to 11.0 million). The limitations to the IPM technologies uptake varied among the regions, but the common ones include a lack of awareness of the IPM technologies, a lack of access to the IPM products, insufficient training, a low involvement of private sectors and a lack of policies for the regulation of IPM technologies. Although significant strides have been made in promoting the fruit fly IPM technologies over the past two decades, our study reveals that the demand surpasses the current supply. Our study recommends a comprehensive strategy for the dissemination and promotion of the technologies through a multi-institutional alliance that enhances public and private partnerships, digital platforms and youth engagement to consolidate previous gains at the regional and continental levels.

Organochlorine pesticide residues in plants and their possible ecotoxicological and agri food impacts

Scientific investigations on levels of Organochlorine Pesticide (OCP) residues in plants largely consider the edible parts (crops, vegetables, and fruit plants). Though the non-edible parts of plants are not eaten by human beings directly, these parts are consumed by livestock and other animals, thereby facilitating the flow of chemical residues through the food chain. The objective of the present investigation was to evaluate the concentration of OCP residues in non-edible plant parts to provide insights on their potential ecotoxicological impacts. Eighteen OCP residues were extracted in nine different plant species (banana Musa acuminate, brinjal Solanum melongena, Casuarina equisetifolia, Eucalyptus globulus, lotus Nelumbo nucifera, paddy Oryza sativa, sugarcane Saccharum officinarum, tapioca Manihot esculenta, tomato Lycopersicon esculentum) following QuEChERS method. The concentrations of OCP residues in plant extracts were determined using Gas Chromatography coupled with Mass Spectrometry (GC-MS). The OCP residues, namely: γ-HCH (lindane), heptachlor epoxide isomer, dieldrin, endrin, endrin aldehyde and endrin ketone were found predominantly in seven plant species. Residues of γ-HCH (lindane) were reported in different parts of plant species such as stem (581.14 ng/g in paddy and 585.82 ng/g in tapioca) and leaf (583.3 ng/g in tomato). Seven samples contained residues of heptachlor epoxide isomer (512.53 to 1173.8 ng/g). Dieldrin was found in paddy stem (489.97 ng/g), tapioca stem (490.21 ng/g) and tapioca leaf (490.32 ng/g). The detected OCPs in the present study were 10-50 times higher than the Maximum Residue Limits (MRL, 0.01-0.1 mg/Kg) as prescribed in the Codex Alimentarius of the FAO/WHO. Their elevated concentrations in the plant parts therefore pose risk of contamination to the consumers in the food chain, including human beings those are dependent on the animals as source of protein. The findings of this study are the first report on residue levels of OCPs in non-edible plant parts in the agricultural landscape of Puducherry region, India. Since, this study assumes significance for the strategic location of Oussudu Lake, an interstate lake spread over Puducherry and Tamil Nadu states, regular monitoring of OCP residues in different environmental segments in strategic locations in both the states is suggested, which will help the authorities in devising a comprehensive environmental management plan aiming at the ecosystem at large.

Health risk assessment of hexachlorocyclohexane in soil, water and plants in the agricultural area of Potohar region, Punjab, Pakistan

In this study analysis of soil, water and plant residue samples is presented to evaluate the contamination levels and possible health risks. Hexachlorocyclohexane (HCH) is a persistent organic pollutant used as a pesticide in agricultural sector for pest control in order to obtain higher productivity. For analysis soil, water and crop residue samples were collected from different agricultural areas of the northern Punjab region of Pakistan. The investigation of the samples shows significant levels of HCH residues in all types of samples. Gas chromatography-mass spectrometry analysis was used to assess the higher residue levels of HCH in the samples. The concentration of HCH residues detected in samples ranged from 2.43 to 8.88 µg/g in soil, nd -5.87 µg/l in water and nd - 4.87 µg/g in plants. The presence of HCH residues in soil, water and plant samples was beyond the recommended quality guidelines. Human health risk was evaluated for cancer and non-cancer risks through dietary and non-dietary exposure routes. The hazard index was HI > 1 in children and HI < 1 in adults, while the non-dietary incremental lifetime cancer risks (ILCR) were beyond the internationally acceptable limit of 1 × 10^-5. Hence, results of the present investigation concluded the presence of high levels of HCH residues in samples and pose high health risk to the inhabitants. These findings are alarming and apprise the concerned departments for the remediation of contamination and proper implementation of environmental laws in the area.