Widely cultivated in Thailand and other Southeastern Asian countries, the garcinia tree (Garcinia mangostana) needs a tropical climate where temperatures remain between 40 and 100 degrees F. The tree's deep purple, white-fleshed mangosteen fruit is a popular wine, candy and jam ingredient. The fruit's pulp and rind are gaining commercial acceptance in nutritional beverage supplements, says Yan Diczbalis of Pacific Island Agroforestry. Although relatively problem-free, garcinia is susceptible to a few pests and diseases.
Tussock moth caterpillars attack new shoots on Philippine garcinia trees and may also be responsible for damage to trees in India, according to the Purdue University Department of Horticulture. A Puerto Rican ant, Myrnelachista ramulorum, damages the trees' new growth by boring into their trunks and branches. Young trees suffer the most damage from these pests. The foliage loss they cause seriously slows the trees' growth. Scars left by feeding red-banded thrips and mites reduce the market value of mangosteen fruit on production-age trees. The most serious fruit damage comes from bats, monkeys and rats that feed on Asian trees.
Puerto Rican garcinia trees growing in humid, shady conditions are susceptible to the thread blight fungus (Pellicularia koleroga). Affected trees have dead stems, matted leaves and fruit covered in webbing. Another fungus, Zignoella garcineae, produces branch growths that kill leaves, branches and sometimes entire trees. Pestalotia fungi cause cankers and shoot tip death in sunburned or weakened trees. Several other fungi impair the trees' ability to store food. Garcinia is also susceptible to sooty mold, leaf spot and stem canker.
Not technically a garcinia disease, gamboge has all the signs of a major one. Trees affected with gamboge have latex--sticky sap--oozing from their branches and fruit surfaces during prolonged wet periods. Fruit rinds absorbing too much water often crack, causing mushy pulp. The oozing and cracking may result from storm-caused bruising, suggests the Purdue Department of Horticulture. Fruit in hot sun, however, also oozes latex. Gamboge can leave mangosteens cosmetically unmarketable.
The most effective means of garcinia pest and disease prevention is to plant healthy trees in optimum growing conditions, advises Diczbalis. Mature trees are more disease-resistant than young ones. Cultivation practices that encourage rapid growth will discourage pests and diseases. Starting trees from seed planted in moist, porous soil and feeding them with urea or ammonium sulfate stimulates growth. Adequate shade, warm temperatures and gradual transition from shade to sun before planting out improves the seedlings' chances of survival to a pest and disease-resistant age.
Pesticides registered to treat garcinia trees are rare. With proper application, however, many copper-based fungicides and widely marketed insecticides can control the trees' usual problems.