Earlier Leaf Flush Associated with Increased Teak Defoliation

The goal of this study conducted at the Mae Mo teak plantation in northern Thailand was to test the hypothesis that early teak (Tectona grandis L. f.) leaf flush results in higher levels of insect defoliation. Based on photographic evidence in both 2010 and 2012, increases in soil moisture in the root zone before the spring equinox resulted in early flushing and subsequent leaf growth and expansion. Early leaf development was observed from 2010 to 2012 in response to wind and distribution of daily rainfall during northerly surges. Adverse growing conditions of shorter day lengths and low soil moisture, in 2001, 2008, 2010, and 2012, were associated with defoliation. The insect that appears to be primarily responsible for defoliation is the teak defoliator, Hyblaea puera (Cramer 1777). In 2011, reduced ambient temperature and a lower vapor pressure deficit reduced evaporative demands during the leaf growing period, resulting in greater soil moisture retention. In 2011, these conditions induced relatively faster leaf expansion and, subsequently, limited the extent of defoliation. There is a strong probability that early leaf flush in response to an increase in premonsoon rainfall was a major factor contributing to teak leaf defoliation over a 12-year period.

day length, leaf flush, leaf growth, soil drought, teak defoliation