Just back from Nan & Phrae yesterday and witnessing Eucalypus die back over several provinces. Somewhat less severe it appears in the degraded hills coming into Lampang from Phrae.
What might the cause be? No sign of insect attack on this exotic unpalatable species. It is said there is only one species of native bird that will consider nesting in a Eucy so not say parrots tearing off leaves and flowers as seen in Australia. No sign of widespread ring barking and hardly likely there is a campaign to poison the trees.
Well what is different this year that may be the culprit. If my mother were still alive she would surely blame the weather. This year has seen the longest wet season in my 12 years in Thailand, with good rains in May, excellent for planting native trees. One might expect the Eucalyptus camaldulensis, also known as the River Red Gum to be prospering. Yes they love to grow near rivers and around swamps and flooding spreads their seed but the Red Gum is also drought tolerant and like Teak needs a period when the ground is dry.
Australia, the land of the Eucalyptus, has seen widespread death from causes as diverse as insect attack and soil compaction by cattle, but the most insidious has been the root fungus Phytophthora cinnamoni which is spread by water in the ground. Can we have advice from a tree pathologist in Thailand?