MANAGEMENT OF DIEBACK DISEASE OF PASSION FRUITS

Passion fruit (Passiflora edulis Sims.) is an important fruit crop grown in Kenya for both local and export markets. Its production is however greatly constrained by diseases including wilt (Fusarium oxysporum f. sp. passiflorae), dieback (Fusarium spp. and Phytophthora spp.), brown spot (), collar rot (Fusarium solani), anthracnose (Colletotrichum passiflorae) and passion fruit woodiness virus disease complex. Yield losses of 80-100% have been attributed mainly to multiple occurrences of these diseases. Surveys done in Kenya in 2007/8 reported dieback to be the most serious disease affecting the crop in all the major growing regions in Kenya with losses of up to 100% being experienced within the first two years of the crops growth. Pathogens isolated from plant materials with dieback symptoms, collected in 5 major growing provinces, included Phytophthora nicotiana var. parasitica and five Fusarium species including F. oxysporum, F. subglutinans, F. pseudoanthophilum, F. solani and F. semitectum. Greenhouse trials were undertaken at the National Agricultural research Laboratories, to determine the effectiveness of pruning, coupled with the use of various fungicides including Bavistin (carbendazim), Cotaf (hexaconazole), Topsin (thiophanate methyl), Ridomil (metalaxyl) and biocontrol agents (Trichoderma harzianum and T. asperellum). Treatments were applied either as sprays or paste on the affected area. All treatments had a significant effect in controlling dieback relative to the control. Carbendazim, hexaconazole and T. harzianum were the most effective treatments, irrespective of the application method. T. harzianum performed better than T. asperellum while thiophanate methyl was better than metalaxyl. On farm evaluation of these treatments would be important in further establishing their effectiveness in controlling dieback disease of passion fruits.