Non-PR | IFPRI4

A summary of the research programme for control of Diaprepes abbreviatus which is primarily responsible for citrus dieback disease. Studies include: population dynamics of the pest, presence of oophagi parasites of which 3 have been discovered in Guadeloupe (Tetrastichus sp. 1 and 2, and Ceratogramma) and one in Martinique (Tetrastichus sp. 3), nematode parasites and fungal parasites. Alternative rootstocks are being tested as well as the effects of soil physical conditions

A citrus rehabilitation programme is underway to restore abandoned estates through weed control, epiphyte and parasitic phanerogam removal, pruning, fertilization and improved drainage. Phytosanitary methods of control of Moko disease (Pseudomonas solanacearum race 2) and Yellow Sigatoka (Mycosphaerella musicola) of bananas are listed. Virus indexing of citrus cultivars has been initiated and research into tissue culture of banana plants started

Moko control in Grenada by eradication of affected and adjacent (buffer zone) mats is discussed. The major constraints to the programme are poor reporting of disease occurrence, inadequate size of buffer zone, need for frequent re-visits to affected farms, uncertainty over the recommended length of the fallow period, and inadequate supplies of Moko-free planting material

Of the citrus diseases occurring in Surinam, fungal, bacterial, viral and those caused by nematodes, tristeza is most important. Trials to identify the best rootstocks to replace the tristeza-susceptible sour orange found Rangpur lime budded with nucellar Alidjan orange best on heavy clay soils. Sunki and King (tangors) are good rootstocks for grapefruit varieties. Research showed tristeza virus transmission by the aphid vector Toxoptera citricidus to be bi-modal (non-persistent and semi-persistent) in Surinam, with the latter more common

The strategy is preventative based on a climatic forecasting system which receives data from 14 agroclimatic stations, complemented by biological assessments. The method used is termed 'state of evolution', an expression of the speed of disease development which varies with inoculum potential and climatic conditions. Benzimidazole and sterol-inhibiting fungicides are applied in rotation

Phytosanitary practices are recommended to reduce the incidence in the Windward Islands of banana pests and diseases: leaf spot (Mycosphaerella musicola), crown rot (Fusarium roseum), virus diseases (bunchy top), moko disease (Pseudomonas solanacearum), banana borer (Cosmopolites sordidus), rust thrips (Chaetonophothrips signipennis), flower thrips (Frankliniella parvula), Lachnopus beetle and nematodes

The tristeza virus and its vector Toxoptera citricidus are present in Guyana, as well as the susceptible rootstock sour orange. Indexing was carried out between 1964 and 1974 and interest was revived in 1982 but this has yet to be resumed

The major banana pests and diseases influenced by poor field management are highlighted. Control of leaf spot (Sigatoka) benefits from a plant density from 1550 to 2100 mats/ha, weed control and detrashing and adequate surface drainage. Nematodes, borers (cosmopolites sordidus), thrips and mosaic virus are reduced by weed control, trash removal and sleeving