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The IPM revolution in the East African flower industry
In three articles published in FloraCulture International beginning Jan 2005, Louise Labuschagne of the Real IPM Company describes the opportunities for the use of natural predators in East African floriculture.
Flower companies near the Equator benefit from year-round growing conditions and high altitudes, which together are the powerhouses of production and quality. Lower labor costs further support profitability and have fuelled expansion at an unprecedented rate in 2004 throughout Eastern Africa.
Kenya has led the expansion in floriculture in East Africa in the last 20 years, but the neighbouring countries of Uganda, Tanzania and Ethiopia are rapidly following suit. Floriculture is seen as a sustainable means of earning foreign exchange and providing sustainable employment for thousands in countries where unemployment is rampant. Governments and donors are co-operating to ensure financial incentives lure investors and technical experts to boost their natural resources (eg, light, soil and man-power).
Kenya dominates the African flower industry and is responsible for about 60% of all flower exports from the continent. Nearly $200 million in cut flowers and foliage are currently exported from Kenya annually, making floriculture the country's third most important foreign exchange earner. Flower exports account for about 14% of the country's exports while providing year-round employment for at least 50,000 Kenyans with another 60,000 to 70,000 in ancillary industries. Rose production is the main focus of Kenya's floriculture and the production area for roses is expected to increase by more than 15% within the next year alone.
Over 94% of the flowers exported from Kenya are destined for markets in the European Union. The largest exporter to the EU, Kenya commands about 25% of that region's market share. Cognizant of 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.
The audit has a number of compliance points which directly relate to IPM (integrated pest management), including a reduction in the use of crop protection products, using IPM on a preventative basis, formal IPM training and other related areas. Not content with taking the lead in production technology, Kenyan growers have been at the forefront in adopting IPM in flower crops. In the last four years the industry has benefited from investment in bioprospecting for indigenous natural enemies for the main pests in Kenya-spider mites, thrips, whiteflies, leafminers and aphids-as well as the development of mass production technology for their natural enemies.
The Kenyan pesticide regulatory authority has devised legal notices, which are appended to the Pest Control Act that cover the registration requirements for natural enemies, biopesticides, botanical pesticides and semio-chemicals. This was achieved within nine months, following a workshop in May 2003, where all relevant authorities, research institutes and the industry came together to devise the Registration requirements with support from EU Registration experts. The speed at which this was achieved is a measure of the support for IPM from the Pest Control Products Board and the Kenyan Agricultural Research Institute.
Kenya already has four natural enemies registered for use: Phytoseiulus (a predatory mite for spider mite), diglyphus (a parasitic wasp for leafminer), Encarsia (a parasitic wasp for whitefly) and Aphidius (a parasitic wasp for certain aphids). Enkasiti Roses in Thika was one of the first companies in Kenya to successfully implement IPM of spider mite in roses. Today, 100% of their crops are grown using IPM for spider mite control.
Several companies are now undertaking the mass production of natural enemies for use on their farms. One of the largest, Homegrown Kenya Ltd, has almost entirely replaced the use of acaricides in roses and dianthus, with the predatory mite Phytoseiulus persimilis. Many other flower companies in East Africa are now following suit.
IPM of spider mites in roses
Spider mite populations in roses and dianthus can reach epidemic proportions in flower crops grown on the equator. The same power which fuels the production of flowers-year-round sunshine-also fuels the growth of spider mites. Over 50% of the annual costs of a crop protection program can be attributed to the control or suppression of spider mites.
While bending roses increases productivity, it also provides 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 and the existence of this "mites reservoir" is why growers have to spray for spider mites routinely, to prevent damage to the crop year in and year out.
The predatory mite Phytoseiulus persimilis is well-known to growers and has been sold in most parts of the world as a biological control for spider mites. Phytoseiulus has the advantage over sprays in that it has legs and actively walks to the underside of leaves, in search of spider mites.
Success is assured as long as enough Phytoseiulus are applied to the crop in relation to the number of spider mites present. Also, be sure care is taken to integrate the predator introduction with compatible insecticides and fungicides. To determine how many Phytoseiulus to apply to a crop, the grower needs to assess the number of spider mites present in a crop. This is achieved by sampling leaves from the base, middle and top of plants and determining the average number of spider mites per leaf. From there it is a matter of a few calculations to determine how many leaves per plant and how many plants per house to estimate the total population of spider mites in the crop.
The speed at which the spider mites are controlled depends on the introduction ratio of Phytoseiulus to spider mites. Best control is achieved if this ratio is at least one Phytoseiulus for every five spider mites.
Growers are often not aware of how many spider mites are actually present in their crop, as this information is not usually used when acaricide programs are employed. However, many growers are now finding IPM scouting methods very useful even in their conventional crops, which use agrochemicals to control mites. The data will also objectively indicate the effectiveness of a particular acaricide in controlling mite numbers.
It takes about 1.5 man hours to scout a 0.25-ha mature rose crop with a moderate population of spider mites, using IPM scouting techniques. With the gradual eradication of spider mites, this process gets quicker. Crops should be scouted a minimum of once per week.
Measuring the progress of biological control
Upon introducing the predatory mite Phytoseiulus persimilis as a biological control for spider mites, the best control is achieved if this ratio is at least one Phytoseiulus for every five spider mites. But how to tell if your efforts are working?
Simply put: data collection. Progress is measured by following the progress of the ratio of Phytoseiulus to spider mites. If the introduction ratio was 1:150 in week one of the program, the ratio should progress to 1:110, then 1:75, then 1:23, then 1:5 and so on. Eventually there will be one Phytoseiulus to every spider mite and at this point the spider mite population will crash to virtually nothing.
Until this time, the spider mites numbers per leaf may have continued to rise, but an experienced practitioner of integrated pest management (IPM) will be confident enough not to spray acaricides in the knowledge that the ratio is coming down and the mites will soon be overcome. There may be some damage during the weaning program, but the advantage of this is that for the first time it will be possible to have virtually no spider mites in the crop.
Growers who lack confidence may choose to intervene and "help" protect the crop through chemical means. Keep in mind, however, even a "safe" pesticide could kill up to 25% of the beneficial Phytoseiulus. Continuous "help" of this kind will prolong the time it takes to achieve control and may cost more in terms of the Phytoseiulus themselves, as it may be necessary to replace the ones killed by sprays.
When the spider mites are decimated, the Phytoseiulus will then attack each other, leaving leaves completely clean. Maintain this spider mite-free zone by enforcing sanitation procedures between clean and unclean zones (reorganizing work plans for harvesting teams, etc).
What about the costs? As the introduction rates depend on the number of spider mites present, an average weaning program may use from 500,000 to 1 million Phytoseiulus. Thereafter, perform routine weekly checks of every row to identify and treat small hot spots as they appear. At European prices for natural enemies, these sorts of introduction rates would be prohibitively expensive. However, beneficial insects can be produced at a tenth of the cost in East Africa.
Louise Labuschagne, Real IPM (labuschagne@realipm.com)
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