Citrus greening disease and tristeza disease are the most serious citrus diseases found in Thailand. The diseases are transmitted by psyllid and a few species of citrus aphid. Affected trees have stunted growth, produce bitter fruits and take months or years to die. In 2010, around 60% of orange orchards in Fang District, of Chiang Mai were damaged by these disease outbreaks. Fang District is a major producer of orange in Thailand, with an area spanning over 100,000 rai (16,000 hectares)
To cope with these diseases, a method of growing disease-free oranges has been developed. Disease-free plantlet is produced through shoot-tip culture. The whole process takes around 1–1.5 year from laboratory to indoor and outdoor nursery and eventual trial plantation.
This method is being validated with MK Farm in Fang District, Chiang Mai.