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Pesticide residues in vegetables will be the end of Sukuma-loving Kenyans

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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.

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