Down the pan

How about I start this week’s blog with a question……what is the common link between the newly-constructed toilet block in Kithimu market place and Maize streak virus (MSV)?

Left: The toilet block at Kithimu market (Credit: Claire Beverley ©CABI) and Right: Maize Streak Virus (Credit: AgBioForum)

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Is citrus greening coming your way?

Mexico is the latest to succumb to the inevitable spread and establishment of huanglongbing (HLB) – the devastating disease of citrus crops. Mexican authorities in the states of Jalisco, Michoacán and Colima have warned growers that HLB – otherwise known as citrus greening – is here to stay.

HLB was first detected in Mexico in July 2009 and it’s clear now that it won’t be going away. Some estimates suggest HLB could affect 60% of Mexico’s citrus industry, an industry which provides employment for 70,000 farmers. SENASICA, the National Service for Animal and Plant Health, Food Safety and Quality, has invested over US$20 million to control the disease. An economic impact assessment report prepared this year by consultants specializing in the economics and finance of plant health programmes indicated total losses to the Mexican economy could amount to almost $7000 million.

Mexico’s not the first to report the alarming consequences of HLB infection. The disease has been known in Brazil for some years and is spreading throughout the region. Florida first reported the disease over 5 years ago and data from 2010 showed 18% of trees in Florida are infected – for more information on the disease in Florida click here. HLB was first reported in Nicaragua and Honduras in 2010 and in Costa Rica in February this year. A recent outbreak in the Dominican Republic is said to have destroyed 34,000 trees and left 5000 unemployed.
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Pest-fighting Anthocyanins

U.S. Department of Agriculture (USDA) scientists in Illinois, USA, are investigating the role of anthocyanins in pest-control. They believe that the plant pigment can adversely affect crop pests such as the corn earworm caterpillar and the cabbage looper caterpillar that feed on it.

Cabbage looper caterpillar. Copyright A. Shelton.

Anthocyanins are a plant pigment which give blackcurrants and flowers, such as petunias, their blue and purple colour. They absorb blue-green and UV light, protecting plant cells from high-light stress.

In the experiments the scientists used corn earworm caterpillars (Helicoverpa zea). H.zea damage is usually serious and costly because of the larval feeding preference for the reproductive structures and growing points which are rich in nitrogen.

The caterpillars were forced to feed on blue areas of petunia petals which contained higher levels of anthocyanins than the white areas. It was found that these individuals gained less weight than other individuals which were fed on only the white leaf areas. Further experiments found that isolated anthocyanins slowed the caterpillar’s growth rate.

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Plant Clinics boost fight against diseases and pests

“Plant clinics boost fight against diseases, pests” – this was the title of a story that appeared in the newspaper Business Daily last week. It was one of many positive articles that were written after a group of journalists were taken to visit some Plant Clinics in Kenya.

The article includes examples where the Plant Clinics have helped farmers in Kenya.

Karanja Kinyanjui, a farmer from Kikuyu District, who supplies Nairobi’s Wakulima Market says he spent Sh10,000 on pesticides prescribed by agro-vets for his potatoes and spinach to no avail. Following this, diagnosis from the plant doctors encouraged him to spray wood ash onto his crops, which, within a week wiped out the disease.

“It still pains me to imagine that the agro-vets fleeced me of my meagre earnings,” he said.

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