At least 60 per cent of patients who visit the Kenyatta National Hospital are found to have pesticide residues in their blood, an aspect attributed to the concentrated chemical pesticides used on vegetables and fruits across the country, a research by Kenyatta University revealed.

Some of the common complaints reported included ataxins, tremors, diarrhoea, vomiting and dermatitis, symptoms that are linked with deltamethrin and lambda-cyhalothrin, which are mostly found in pesticides and herbicides.

This findings of the study confirmed those of another done earlier by the Referral hospital in 2003, which ranked  pesticides as the leading cause of food contamination and poisoning in the country.

The latest study sampled pesticide residues on two types of vegetables: kales (Sukuma Wiki) and cabbages, which are the most popular choice in urban and rural Kenya.

It found out that vegetables consumed in urban setting had high pesticide and insecticide contents compared to those in rural areas. According to the study, there were high pesticide residues on vegetables during dry seasons than there were when it rained. During the dry season, mean residue levels ranged between 0.0130 and 0.3400 mg/kg and between non detectable level and 0.1100 mg/kg during the wet season. The low pesticides residue levels during wet seasons were attributed to wash off effect of the pesticides by the rainwater and minimal application of pesticides by farmers due to few pests than during the dry seasons.

Most of the vegetable samples analyzed in the study had deltamethrin and lambda-cyhalothrin residue levels exceeding the Acceptable Daily Intake (ADI) and higher than maximum Residue Limits (MRL) as set by the World Health Organization (WHO).

In a bid to tackle this growing health hazard considering that vegetables are widely consumed by people across the globe since they are vital in providing vitamins and minerals in
diet, besides supplying protein and energy, a group of researchers from the Kenya Agricultural and Livestock Research Organization (KALRO), led by Vincent Ochieng, are advocating for the use of biological control methods such as parasitoid, biological pesticides and good agronomic practices in order.

Such methods, they argue, increase production, lower production costs and minimize health hazards caused by the use of chemical pesticides and herbicides.

In their study, titled Promoting Sustainable Vegetables Production for Enhanced Incomes and Food Security in Kenya, Ochieng and his team developed projects in five ecological regions in the country with the aim of testing available technologies and developing appropriate packages for dissemination to farmers. 

They planted cabbage variety Prucktor F1 using both organic and inorganic methods  in Muguga, Ndeiya, Busia, Kibos and Njambini, maintained and sampled the data collected on pest and disease incidence, growth vigor to maturity, yields, size and distribution.

The study found out that when bio fertilizers were used, higher yields were achieved compared to when synthetic fertilizers were applied. An average sample from all five sites showed a 52 per cent production when bio fertilizers are used compared to an average of 45 per cent when synthetic fertilizers are used. The casual way of production where neither synthetic nor bio fertilizers are used recorded the least production levels of 25 per cent.

In a separate study to determine the effectiveness of biological control of pests and insects in vegetables compared to chemical pesticides, the researchers intercropped cabbages with onions. In order to get best results, they intercropped two rows of cabbage with a row of onion, three rows of cabbage with a row of onion and four rows of cabbage with a single row of onions. During the growth stages, cabbages in all three samples were attacked by diamond black moth, cabbage aphids, cabbage web worm and white fly. However, the number of instances was more in four row cabbages intercropped with a single onion row than in two row cabbage intercropped with a single row of onion. The Parasitoids that had reared both the laboratory and high tunnel rearing units at KALRO Muguga south and Mwea were released in Busia County. The results indicated that production of parasitoids recovered from cocoons of diamond back moth, increased from slightly over 40% to 100% in less than three month after introduction of the parasitoids. In the released sites D. Semiclausum and Cotesia plutellae had established, having the highest parasitism levels.

The study concluded that, onions can be used as an intercrop in the management of cabbage pests. The fact that reduction in pests’ numbers and significant increase in yield were achieved without the use of insecticides was an indication that when adopted by the small to medium scale farmer it would improve yield and increase the incomes of farmers. It was also discovered that the use of parasitoids was good and less costly to vegetable farmers whereby they didn’t need to use pesticides to control key pests; they also conserve the environment by maintaining the population around their fields and no pesticides residues.

With the Kenyatta National Hospital study published in the East and Central African Journal of Pharmaceutical Sciences indicating that pest and insecticides account for 43 per cent of food poisoning in Kenya with a mortality rate of seven per cent, its perhaps high time agricultural stakeholders inform vegetable farmers the relevance of biological means of controlling pests and insects as opposed to chemicals in order to arrest the growing health problem that is slowly eating into the lives of vegetable consumers in Kenya.