Pesticide usage practices as sources of occupational exposure and health impacts on horticultural farmers in Meru County, Kenya.

This study assessed pesticide usage practices, knowledge and health effects of pesticides through occupational exposure in randomly selected horticultural farmers in Imenti North, Imenti South and Buuri Sub-counties in Meru, Kenya, where horticultural crops are grown intensively for export and local consumption. The study was done through use of questionnaire distributed to farmers' households, agricultural extension workers and health care workers. The survey established that various classes of pesticides were used in horticultural crop farming and animal production in all the three sub-counties, with the most frequently used (>60 respondents out of 173) being parathion, diazinon, dimethoate, permethrin, pirimiphos methyl, endrin, deltamethrin, dieldrin, propoxur and endosulfan. It was found that there is a gap between the existing government regulations on pesticide use and safe handling and the implementation of these regulations by dealers, farmers and farm workers in the three sub-counties as some of the pesticides that were being used such as parathion, endrin, dieldrin and carbofuran had been banned by the government. Although most farmers had general information on pesticide usage through various social groups and contact with agricultural extension workers, only 32-43 % of the farmers had received training on pesticide handling and use. Most farmers (65%) had knowledge of safe pesticide handling procedures including reading labels on packages and wearing protective clothing; but many farmers (44% in Buuri, 57% in Imenti South and 60% in Imenti North) did not wear the requisite protective clothing when applying pesticides. The agricultural extension workers (52%) and health care workers (59%) were trained in their work and had at least a certificate level qualification from a tertiary institution. Most agricultural extension workers (95%) and health care workers (71%) had experience of dealing with pesticides and knew how to administer 1st AID against pesticide poisoning, respectively. Farmers (26%) reported experiencing health effects after using pesticides, with most effects being felt after using dimethoate, malathion, carbofuran, carbaryl and heptachlor. There was a statistically significant (p < 0.05) association between various factors (availability of protective clothing, hiring of labourers, farm land size, expenditure on pesticides and expenditure on treatment, respectively) on intoxication from pesticide exposure.

Occurrence of pesticides residues in French beans, tomatoes, and kale in Kenya, and their human health risk indicators.

Residue levels of seven commonly used pesticides were determined in random samples of tomatoes, French beans, and kale collected from horticultural farms in Buuri, Imenti North, and Imenti South sub-counties in Meru, Kenya, just before delivery to the consumers. QuEChERS method for extraction followed by LC-MS/MS was used to determine the concentrations. The concentrations (µg kg-1 wet weight) in French beans, kale, and tomatoes ranged from below detection limit (BDL): BDL-48.65 (carbendazim), BDL-290.76 (imidacloprid), BDL-2.81 (acetamiprid), BDL-25.76 (azoxystrobin), BDL-105.18 (metalaxyl), BDL-0.15 (diazinon), and BDL-0.17(chlorpyrifos). The maximum residue levels determined in the horticultural produce from the three regions were 290 µg kg-1 for imidacloprid in tomatoes from Buuri and 25.76 µg kg-1for azoxystrobin in French beans from Imenti South. The pesticide residue levels generally were extremely low and met the MRLs set by EU and other countries, except for carbendazim and metalaxyl in French beans, and posed no concern to human health. The estimated daily intakes (EDI) (mg kg-1 BW/day) for the population of Meru County were very low ranging from 1.685 × 10-8 (acetamiprid) to 2.381 × 10-5 (imidacloprid) in tomatoes, 2.849 × 10-9 (metalaxyl) to 3.633 × 10-7 (azoxystrobin) in French beans, and 1.392 × 10-8 (diazinon) in kale, respectively. The health risk indices were subsequently extremely low for the detectable pesticide residues, ranging from 6.74 × 10-7 (acetamiprid) to 3.97 × 10-4 (imidacloprid) in tomatoes, 3.56 × 10-8 (metalaxyl) to 5.52 × 10-5 (chlorpyrifos) in French beans, and 6.96 × 10-5 (diazinon) in kale, respectively, indicating no health risk in the population, but their presence in these vegetables cannot be ignored as long-term exposure can still cause health risks.

The effect of synthetic pesticides and sulfur used in conventional and organically grown strawberry and soybean on Neozygites floridana, a natural enemy of spider mites.

BACKGROUND: The beneficial fungus Neozygites floridana kills the two-spotted spider mite Tetranychus urticae, which is a serious polyphagous plant pest worldwide. Outbreaks of spider mites in strawberry and soybean have been associated with pesticide applications. Pesticides may affect N. floridana and consequently the natural control of T. urticae. N. floridana is a fungus difficult to grow in artificial media, and for this reason, very few studies have been conducted with this fungus, especially regarding the impact of pesticides. The aim of this study was to conduct a laboratory experiment to evaluate the effect of pesticides used in strawberry and soybean crops on N. floridana. RESULTS: Among the pesticides used in strawberry, the fungicides sulfur and cyprodinil + fludioxonil completely inhibited both the sporulation and conidial germination of N. floridana. The fungicide fluazinam affected N. floridana drastically. The application of the fungicide tebuconazole and the insecticides fenpropathrin and abamectin resulted in a less pronounced negative effect on N. floridana. Except for epoxiconazole and cyproconazole, all tested fungicides used in soybean resulted in a complete inhibition of N. floridana. Among the three insecticides used in soybean, lambda-cyhalothrin and deltamethrin resulted in a significant inhibition of N. floridana. CONCLUSION: The insecticides/ acaricides abamectin and lambda-cyhalothrin at half concentrations and fenpropathrin and permethrin and the fungicide tebuconazole at the recommended concentrations resulted in the lowest impact on N. floridana. The fungicides with the active ingredients sulfur, cyprodinil + fludioxonil, azoxystrobin, azoxystrobin + cyproconazole, trifloxystrobin + tebuconazole and pyraclostrobin + epoxiconazole negatively affected N. floridana. © 2015 Society of Chemical Industry.

Effect of trichomes on the predation of Tetranychus urticae (Acari: Tetranychidae) by Phytoseiulus macropilis (Acari: Phytoseiidae) on tomato, and the interference of webbing.

The two-spotted spider mite, Tetranychus urticae Koch, is an important pest of tomato in different parts of the world. Biological control of this pest on this crop has not been very successful. Phytoseiulus macropilis (Banks) has been used commercially for the control of T. urticae on different crops, but no information has been published on its potential to control T. urticae on tomato. The objective of this work was to compare the performance of a Brazilian population of P. macropilis on tomato with its performance on other plant species, relating the observed variation to the respective types and densities of trichomes. It has been hypothesized that the presence of the webbing produced by T. urticae could help the predator to avoid contact with trichomes and consequently to improve its performance on tomato plants. This hypothesis was also evaluated. Phytoseiulus longipes Evans was included in the work as a control, given that it has been reported to be a promising predator of Tetranychus species on tomato. The study was conducted under laboratory conditions. It was found that the performance of P. macropilis was similar to that of P. longipes and that trichomes hampered the locomotion as well as prey consumption and oviposition rate of both predators; that the presence of webbing resulted in higher levels of prey consumption and of predator oviposition; and that the presence of webbing eliminated the negative effect of trichomes of eggplants and partially eliminated the negative effect of trichomes of the 'cerasiforme' tomato variety. The observed density of trichomes in 'Carmem' one of the most common tomato varieties grown in Brazil, seems not to have interfered significantly with the prey consumption and the oviposition rate of P. macropilis. The results suggest that the latter is a promising predator of T. urticae on tomato. Complementary studies are warranted, to further evaluate the potential of P. macropilis for use as a biological control agent of this pest.

Role of entomopathogenic fungi in the control of Tetranychus evansi and Tetranychus urticae (Acari: Tetranychidae), pests of horticultural crops.

The spider mites Tetranychus urticae Koch and Tetranychus evansi Baker and Pritchard are important pests of horticultural crops. They are infected by entomopathogenic fungi naturally or experimentally. Fungal pathogens known to cause high infection in spider mite populations belong to the order Entomophthorales and include Neozygites spp. Studies are being carried out to develop some of these fungi as mycoacaricides, as stand-alone control measures in an inundative strategy to replace the synthetic acaricides currently in use or as a component of integrated mite management. Although emphasis has been put on inundative releases, entomopathogenic fungi can also be used in classical, conservation and augmentative biological control. Permanent establishment of an exotic agent in a new area of introduction may be possible in the case of spider mites. Conservation biological control can be achieved by identifying strategies to promote any natural enemies already present within crop ecosystems, based on a thorough understanding of their biology, ecology and behaviour. Further research should focus on development of efficient mass production systems, formulation, and delivery systems of fungal pathogens.

Pathogenicity of Beauveria bassiana and Metarhizium anisopliae to the tobacco spider mite Tetranychus evansi.

Seventeen isolates of Metarhizium anisopliae (Metschnikoff) Sorokin and two isolates of Beauveria bassiana (Balsamo) Vuillemin were evaluated for their pathogenicity against the tobacco spider mite, Tetranychus evansi Baker & Pritchard. In the laboratory all the fungal isolates were pathogenic to the adult female mites, causing mortality between 22.1 and 82.6%. Isolates causing more than 70% mortality were subjected to dose-response mortality bioassays. The lethal concentration causing 50% mortality (LC5o) values ranged between 0.7 x 10(7) and 2.5 x 10(7) conidia ml(-1). The lethal time to 50% mortality (LT50) values of the most active isolates of B. bassiana and M. anisopliae strains varied between 4.6 and 5.8 days. Potted tomato plants were artificially infested with T. evansi and treated with B. bassiana isolate GPK and M. anisopliae isolate ICIPE78. Both fungal isolates reduced the population density of mites as compared to untreated controls. However, conidia formulated in oil outperformed the ones formulated in water. This study demonstrates the prospects of pathogenic fungi for the management of T. evansi.