Magdalene Wanza and Dr. Maina Mwangi Department of Agricultural Science and technology, Kenyatta University, P. O Box 43844-00100, Nairobi, Kenya. MANAGEMENT OF CROWN GALL DISEASE IN THE PRODUCTION OF FLOWER CUTTINGS IN KENYA     2nd Phytosanitary conference ,KEPHIS headquarters, Nairobi 4th-8th June,2018.

Introduction Horticulture sub-sector is one of the top foreign exchange earners. The growth rate averages 15-20% per annum (FPEAK, 2015). Flowers accounted for 69.8% of the value of horticulture exports (KNBS,2017). Flowers produced in Kenya are marketed as Cut flowers, e.g roses or flower cuttings mainly in Europe. Flower cuttings constitute a variety of different flowers: -Chrysanthemum -Argyranthemums - Leucanthemums - Poinsettias - Pelargoniums

Crown gall disease Plant Diseases are among the serious challenges to the agricultural sector in Kenya. Crown gall is caused by Agrobacterium tumefaciens. It is the most widely distributed bacterial disease of plants in the world (Hudelson and Joy,2005). It affects more than 100 species of fruit crops, woody and herbaceous ornamentals. Induces galls, reduces yield, destroys vascular tissues, causes dieback or plant death. It reduces the marketability of nursery stock (Deacon, 2015). In Kenya, it is a major threat to roses, Chrysanthemums, Argyranthemums, Leucanthemums etc Crown gall was introduced in 1998 through infected rose root stock from Israel. Currently it is widely spread in nurseries, commercial production areas and in uncultivated fields

Infected plants Rose flower plant showing chlorotic symptoms Infected mother plants for production of flower cuttings

More infected plants

Management of crown gall Producers have tried various management strategies against the disease (KFC,2011). Prevention of inoculum introduction, Use of nursery stock free of galls near the crown, Sterilization of propagation substrate with chemicals, heat or antibiotics (KEPHIS, 2017). Use of bio-pesticide based products such as neem oil that have temporarily managed Crown gall(Kado, 2002). Use of AB spray composed of vegetable soap, essential oils and fermented plant extracts has been used for coating and drying galls in roses (Kado, 2002).

Cont. Biological control has been tried with Agrobacterium radiobacter (Farrand, 1990). Copper based compounds have been used with temporal effect (Judith,2010). Dipping of seedlings in a bactericide at transplanting, e.g. Use of Creosote-based compounds strong oxidants such as Sodium hypochlorite is ineffective (Burr,2004). Antibiotics and Copper bactericides can kill the bacterium on contact, …but they do not penetrate plant tissues to come into contact with bacteria residing endophytically (Burr, 2004).

Challenge Crown gall remains a major challenge in East Africa (Maina et al, 2011). Limited research done on effectiveness of various management strategies. Chemicals largely avoided due to health and environmental concerns health risks resulting from occupational exposure residues on food Pollution of drinking water (Damalas and Ilias, 2011). Better management strategy with less pesticides use needed.

Ongoing research Electro-chemical activated water, commonly abbreviated as ECA water ECA is a concentrated solution that has many disinfecting properties Ozone, chlorine, hypochlorous acid and other biocidal agents that kill crop pathogens ECA water is harmless to the environment Proven wide target range: bacteria, root and fungal diseases, viruses and biofilm. Rheum officinale composed bio-pesticide that manages fungal and bacterial diseases Foliar application solution containing colloidal copper. Copper oxychloride contains 50% metallic Copper. Mode of action is contact. Vegetable oil. Manages agrobacterium by suffocation.

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