However, in recent years, biological limitations associated with the widespread cultivation of L. leucocephala have become evident. These include lack of drought tolerance, poor growth on acid soils, low wood durability, heavy pod production and susceptibility to an insect defoliator (Heteropsylla cubana). These limitations are partly attributed to the narrowly based genetic material that has been used in most planting programmes, due to three main factors: 1) the species is largely self-pollinating and therefore inbreeding; 2) there is a lack of knowledge of its natural distribution, believed to be in Guatemala and Mexico, and hence where more variation may occur; 3) cultivated material is derived from a few closely related cultivated trees in Mexico and El Salvador.