Predatory mite offers reprieve for flower firms against voracious spider mite

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Published on Wednesday, 14 December 2011 11:17

A biological method to control the voracious and dreaded spider mites in rose flowers is repositioning East African flower firms, which were previously struggling to meet the strict quality standards of European markets aimed at curbing the use of pesticides in the exported flowers.The new biological tool, using the spider mite's predator, Phytoseiulus persimilis,

on the highly competitive rose-growing farms of Kenya has also resulted in significant cost savings, as well as improvements in leaf and bloom quality, and reduced the risk to the environment and workers from being exposed to pesticides.

 Bending rose flowers provide a safe haven for spider mites as chemical sprays cannot reach the underside of the leaf. As a consequence, in spite of effective spraying in the upper canopy, spider mites continue to migrate upwards from the base of the plant meaning that flower growers have to spray repeatedly for spider mites to prevent the "mites reservoir" from causing damaging the crop every year.

However, the predatory mite Phytoseiulus persimilis actively searches the underside of leaves for the spider mites, and provides an effective biological control at a ratio of at least one Phytoseiulus
for every five spider mites.

Enkasiti Rose Farm in Thika District was among the pioneer users of the natural enemies to replace pesticides, back in 2004, with impressive results. The flower company had long struggled with mites,
with an estimated 10 million attacking every hectare of roses. The problem is now resolved.

Covering 28 hectares that produce 18 varieties of rose flowers, the company produces 48 million long-stemmed blooms a year, which are carefully checked and packed before being air-freighted to the Dutch flower auctions in Europe.

"Our customers want beautiful tight buds but they also want glossy, dark green leaves with no damage," said production manager Mr Narayana, "which is why 70 per cent of our pesticide use was against red spider mite. And with such intensive use of chemicals we were concerned about the development of resistance."

The rose growth for the company has also now improved, following from the plants being relieved of the stress effects from repeated insecticide use, and Enkasiti’s blooms have moved up a quality grade
in the Dutch auctions. Their strong position in the market reflects the increasing concern over pesticide use among European buyers, which has led to tightening of regulatory standards for environmental
protection and worker safety.

Over 94 per cent of the flowers exported from Kenya are destined for markets in the European Union. The largest exporter to the EU, Kenya commands about 25 per cent of that region's market share. Following rising criticism of environmental damage and operator health safety issues in floriculture, European retailers have recently developed an audit of Good Agricultural Practice in Ornamentals and Flower production-Eurep-Gap.

While Eurep-Gap is not a legal requirement for entry into the EU market, it is an essential part of the business relationship between suppliers and retailers, since it defines Good Agricultural Practice and reduces the likelihood of negative publicity regarding production methods of suppliers, which can seriously impact on sales.

Following the success for Enkasati, several companies are now undertaking mass production of the natural enemies for use on their farms. One of the largest flower companies, Homegrown Kenya Ltd, has almost entirely replaced the use of acaricides in roses and dianthus, with the predatory mite Phytoseiulus persimilis, and many other flower companies in East Africa are now following suit.

Written by Bob Koigi for African Laughter

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