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INFESTATION: Managing the invader fruit fly

They attack the fruiting living tissue of a plant where the female lay eggs by inserting them under the skin of fruits and vegetables during growth.
Fruit and vegetable producers and exporters in Kenya are suffering massive losses due to the African invader fly (Bactrocera invadens) and other fruit flies.
Fruit damage and trade restrictions on Kenya’s fresh produce known to be hosts to certain fruit flies pests’ continue to rise. South Africa banned imports of Kenyan avocados, mangoes and other hosts of the invader fruit fly in April 2008.
According to the Horticultural Crops Development Authority (HCDA), Kenya exported 274,908kg of avocados worth Ksh21.4 million in 2007 and is currently unable to export about 300,000kg yearly to South Africa.
A presentation by Tiffany Wax (University of Washington) on “the Environmental and Economic Impact of the Invasive Fruit fly in Kenya” indicate that avocados worth $2.1 million (Ksh167.16 million) were exported to South Africa in 2007 but the export dropped by 80% in 2008.
ICIPE estimates that 760,000
the invader fruit fly was first detected in Kenya in 2003 by iCiPE scientists but it is not yet clear when and how it got to Kenya, but has rapidly spread to most parts of the country.

“About one-fifth of invasive ‘ species may cause extensive economic and ecological damage with unpredictable negative effects on native populations that are second only to habitat destruction,” Dr.
In addition to South Africa, other markets Sunday Ekesi, the African Fruit¬
tonnes (760 million kg) of man-like the Seychelles, Mauritius, USA, Japan fly Programme (AFFP) leader goes are lost yearly due to various fruit flies. It is estimated that fruit export restriction to South Africa
and EU have imposed restrictions or increased entry checks. ‘at the International Centre of Insect Physiology and Ecology (icipe). alone costs Kenya up to $6 million (Ksh477.6 million) annually.
In addition to South Africa, other markets like the Seychelles, Mauritius, USA, Japan and EU have imposed restrictions or increased entry checks, unless an official treatment is applied before shipment or produce is grown in a fruit fly pest free area that could be certified by KEPHIS.
The horticulture sub-sector generated $1 billion (Ksh79.6 billion) in foreign exchange and over $650 million (Ksh51.7 billion) in domestic earnings in 2008 according to HCDA, directly and indirectly employing over four million people but continued flow of such earning is being rapidly eroded by the fruit fly. The industry is at risk of failing to contribute as expected towards the GDP, Millennium Development Goals (MDGs) and

Vision 2030.
Trade bans and barriers from trading partners where the fruit flies are absent or their full establishment officially in check get imposed in accordance with the World Trade Organization’s Sanitary and Phytosanitary (WTO-SPS) agreements and the International Plant Protection Convention (IPPC) principles on prevention of introduction and spread of pests. Every country has the responsibility to protect its territories from invasion by foreign pests.
The invader fruitfly(B. invadens) was first detected in Kenya in 2003 by ICIPE scientists but it is not yet clear when and how it got to Kenya, but has rapidly spread to most parts of the country. It is now reported in at least 28 African countries-the latest being first detection in May this year by the elaborate surveillance in South Africa by their National Plant Protection Organization (NPPO). It is obligatory under the WTO -SPS and IPPC treaties that such information is made public inter¬nationally by the respective NPPO

or its equivalent which is man-dated to protect the introduction and spread of pests and noxious weeds.
Avocado has been recorded as a host of B. invadens but KEPHIS (Kenyan NPPO) has not yet in¬tercepted any consignment be¬cause of the pest. A recent study indicates that the Hass avocado variety is a conditional non-host

for Ceratitis capitata and a poor but potential host for the related
C. rosa and C. Cosyra (Jour. Econ. Entomology), and so no risk miti¬gation necessary for C. capitata on the Hass. C. cosyra had for long been the most serious fruit fly pest on mangoes while others in the genus are C. rosa and C. capitata. These indigenous species could cause direct damage of 40%-80% on mangoes depending on locality, variety and season. However, since the detection of the invasive species from Sri-Lanka in 2003, it has rapidly displaced the native species in much of the country, taking over as the foremost threat to production and trade of various host fruits.
The fly’s economic implications have a heavy impact on high value horticultural crops such as man¬go, avocado, guava, cucumber, pumpkin, melon, tomato, ripe bananas, pepper, citrus and cashew nuts. It seriously threatens the income, food security and livelihood of millions of families that produce and trade in fruits and vegetables.
Studies by KEPHIS, Ministry of Agriculture, KARI and ICIPE have shown that it is mainly a low-to¬midland pest occurring below
1700m above sea level but its range keeps on spreading.
indirect losses are more significantly felt by the farmers because of instant loss of market and revenue for ready fruits.

Females insert eggs under the skin of fruits and hatch into whitish-cream larvae (maggots) that feed on the flesh of the fruit or vegetable causing direct damage and subsequent rotting due to secondary infection of the affected parts.
Indirect losses are more significantly felt by the farmers because of instant loss of market and revenue for ready fruits. The larvae is the most damaging stage of fruit flies and one of the stages that can easily move with fruit or vegetables in trade.
“It is very frustrating to painstakingly produce good fruits then have them rejected on the basis that they might have a certain new worm, yet we regularly spray with various insecticides”, lament¬ed a farmer who used to sell for the export market.
The worms might not be evident at harvesting but may develop from previously laid eggs. “We
have noticed an increase in ripe mangoes having worms in our shelf-life trials but I don’t under¬stand why South Africa banned our avocadoes”, commented one quality controller who works in the pack house of a fruit exporter.

The ban by South Africa is considered unfair by many Kenyans as the more stringent EU market is still open, albeit with increased checks. The insect is of tropical origin and could possibly establish better in the tropics than the temperate countries. South Africa has a vibrant grape, avocado and citrus industry that could be devastated by the invader fly that has not yet been established there.
Concerted efforts are being
made to regain the fruit market with the understanding that eradicating a well-established pest with high reproduction rate, readily available hosts and suitable environmental conditions is not an easy task.
Prof. Christian Borgemeister (Director General, ICIPE) told a recent conference that long term management of the fly requires an integrated approach that explores and utilizes available options including cultural methods, biological and chemical insecticides to suppress the population, reduce chances of infestation by observing orchard sanitation
where infested fruits should be disposed in a manner that prevents the worms from developing into adults, keeping the fly away from the fruits (eg, covers over mature/ripening fruits) or applying a phytosanitary treatment to the produce after harvest.
The biology and behaviour of the invader fly makes it hard to control using conventional insecticidal sprays. Strong insecticides with long residual effect or persistent systemic action could kill adults landing on treated plants, the eggs and young worms developing in the fruit. Unfortunately, the chemicals might make fruits unsuitable for human consumption or have residues exceeding
the maximum acceptable levels. This becomes a food safety issue that many countries are unlikely to compromise.
Processing and packing of fruit juices should be encouraged to utilize the good fruits under restriction or ban, and then marketed because the juice is not under quarantine.
Various local firms dealing in crop protection services and pest control products are actively involved in the search of appropriate products that will assist the horticulture industry deal with the fruit-fly problem.
ICIPE’s AFFP programme and KARI have identified various male attractants and food baits that could be utilized for suppress.

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