West Indies Mahogany: Interactions

The Shoot Borer

A main hindrance to the growth of this species has been damage by the shoot borer⁹. The mahogany shoot borer, Hypsipyla grandella, bores in twigs and seed capsules of trees in the mahogany family (Meliaceae), especially S. mahagoni.  It has been a concentrated subject of research in several tropical countries, as it is an important economic pest. Larvae of Hypsiplya grandella attack the seed capsules of West Indies mahoganies in spring (March-April after the capsule’s seeds were exposed¹ . Therein which they hollow out seeds. The hardness of the capsule valves is an apparent a factor in preventing penetration by the larvae, however. Although the larvae can attack new shoots, the seed capsule contents appear to be the preferred food source. When both were available, there were higher percentages of dehisced seed capsules than new shoots that were attacked. The insect's most severe damage to trees occurs when a larva bores into and kills the terminal shoot. A lateral branch grows upward to replace the lost terminal shoot, resulting in a crooked main stem.

    Mahoganies growing in natural forests often occur at low densities and mixed with many other species. Under such conditions they are less likely to be attacked by mahogany shoot borers. However, as there are nurseries in Florida containing many of these trees in order for the dispersement of their ornamental value, these trees are more likely to be attacked. By planting mahogany trees with resistant genotypes, the management of shoot borer damage could be effective. In the tropics, mahogany shoot borers are active all year.

Even thought there has been research conducted in 23 tropical countries over the past eight decades, no reliable nor cost-effective control method has been found to prevent economic damage by these insects. There are about 40 species of insects that are natural enemies of the mahogany shoot borer, which are also native to the region, but their effect has been insufficient in preventing damage done to the trees.

 

The Web Worm

The mahogany webworm, Macalla thyrsisalis, is a moth species whose caterpillar is a defoliator of West Indies mahogany in Florida. The caterpillars are a striking yellow color, and spin extensive webbing in the spring, when they are most prevalent. 

 

 

    The larvae  spins a web, pulling several leaves together and consume leaf tissue of the host plant. The larvae feed primarily on young, immature leaves, completing its stage in about ten days.

Although both the tree and insect species are native to this region, the larvae will, however, feed and develop on the foliage of some other species of Meliaceae (such as Honduras mahogany) if placed on it.

Most defoliated trees quickly produce new foliage which remain free of webworms for the rest of the growing season. It is doubtful that the spring defoliation, even when extensive, has an effect on health and growth of West Indies mahoganies of significance for shade trees¹⁵.

In southern Florida and  throughout its native range, the mahogany webworm is under natural control. One parasitic fly species, Lespesia and two species of parasitic wasps, Habrobracon  and Apanteles  are natural enemies of mahogany webworm in Florida.

The Cattle Egret

   There has been no significant studies done on a specific species of bird roosting in Mahogany trees, however, a peculiar case of the Cattle Egret was found to inhabit one tree in particular.

   Cattle Egrets were not documented to breed in  in urban areas until 1986, when they nested in a single West Indian mahogany (Swietenia mahagoni) a site they have continuously occupied to the present until their nests (and contents) were destroyed in July 2004 ⁵.

 

Humans

It is undeniable that humans, of all organisms, have had the largest affect on West Indies mahogany. Because of the great commercial value the wood contains, this tree has become threatened, struggling to repopulate despite the aid of conversationalists. Check out the sustainability page to learn more.

 

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