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PestNet is a network that helps people worldwide obtain rapid advice and information on crop protection, including the identification and management of plant pests. It started in 1999. Anyone with an interest in plant protection is welcome to join. PestNet is free and is moderated, ensuring that messages are confined to plant protection.
Crops > Trees, palms & pandanus > Trees > Cupressus dieback, St Lucia
November 2006. Trees of Cupressus spp. in Saint Lucia, West Indies, which are used as Christmas tree, are suffering from progressive browning of the stem, branches and floral organs. This can be seen from the nursery to the field. It does not seem to be associated with mites or insect pests, nor with pathogens. The problem starts at the base and progresses upwards. The batch of seeds was obtained in 1994–1996. The problem has shown up in various locations throughout the island.
From the photo, there may be a lack of mycorrhiza. In Pinus, lack of mycorrhiza is first seen in the nursery and, later in the field, the plants just do not thrive. If they obtain the mycorrhiza in the field, they will suddenly grow, although others may still be stunted. A solution is to look for puffballs under well grown trees, make a slurry of the spores (rub them into dishwashing detergent first to make them disperse in water) then water the slurry over the seedbeds. Puffballs are easier than the mushroom-type mycorrhizal fungal species as it is possible to obtain large amounts of spores very easily. Also, look at the roots of healthy plants and see if there are any coralloid roots as an indicator of ectomycorrhiza.