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Attack by shootborers on the Meliaceae such as Swietenia, Khaya, Lovoa, Cedrela, Carapa and Entandrophragma is common in all tropical countries. It causes considerable damage to plantations in varying intensity among individual countries and regions. Young plants from 2 years on are attacked, but also trees 10 to 20 years are often damaged in later years. The insect is a small lepidopterous pyralid of the genus Hypsipyla of which there are three species worth mentioning: Hypsipyla grandella in America, Hypsipyla robusta in Africa and Asia, Hypsipyla albipartalis in Uganda. It generally lays its eggs on young shoots at the base of the leaf petioles, and in northern India it is found on the fruits of Cedrela toona. The larvae, which penetrate immediately into tissues, are sensitive to insecticides for only a very short time, probably not over several hours. They hollow out the young shoots for a length of about 60 centimeters and can even attack several shoots. The cycle lasts from 4 to 10 weeks, beginning in the rainy season, with a minimum of two generations per year. However, less severe attacks may occur during the entire year.
Damage is very important and has caused considerable losses which limit large-scale planting of the Meliaceae in tropical countries. Such damage appears to be greater on Cedrela than on Swietenia in Latin America, and greater on Swietenia macrophylla than on Swietenia mahogani in plantations in Indonesia. The damage consists of death of the young terminal shoots, considerably retarding growth, and results in the formation of numerous secondary shoots causing twisted and unthrifty trees. This, however, does not cause the death of the entire tree. The following figures can be cited: in Puerto Rico from 1935 to 1943, one million Cedrela and 835,000 Swietenia trees were damaged; and, at Tingo Maria in Peru, 60 percent of the Cedrela and 10 percent of the Swietenia were attacked over the same period.
Control is particularly difficult in view of the short duration of the external life of the larvae. Chemical treatment seems to be limited, until now, to forest nurseries. In Peru, a 0.5 percent DDT solution or a lead arsenate paste, and, in Malaya, DDT solutions have been used. In plantations, only silvicultural measures have been employed. The problem is very complex and although many methods have been recommended, none have proved satisfactory until now. These methods consist generally of avoiding use of too close spacing or pure plantations, and of choosing favorable site conditions which will permit the tree to pass quickly the stage at which attack is most likely to occur. A certain degree of cover should be maintained because the development of the insect is favored by light. However, in the latter case the gauging of the light is difficult in view of the need of the Meliaceae for sufficient light for development; excessive shade has been blamed for numerous plantation failures.
A parasitic Ichneumonid (Calliephialtes) has been mentioned in Puerto Rico; in India, 11 parasites have been found; the most important (Trichogramma minutum) lives on the eggs of Hypsipyla robusta. But until now no adequate study has been made of the biological control of Hypsipyla.
Cedrela in Latin America
Plantations of Cedrela mexicana, C. odorata, C. fissilis, C. lilloyi, and C. tubiflora all appear to have been attacked by Hypsipyla grandella, particularly the first two mentioned species, which are well known. This pest is associated with poor drainage of the soil or sunscald of the collar, which renders the plant susceptible to attack by a buprestid. Frequent heavy failures are expected in most plantations leading either to limiting planting to exceptionally favorable terrain, as in Trinidad, or even in certain cases abandoning such plantations altogether.
To combat this disastrous situation, Holdridge (1943) advises for the Caribbean area the planting of a maximum of 60 trees per hectare on carefully chosen sites. He notes that Hypsipyla grandella does not tolerate shade but as it can reduce the growth of Cedrela; he thinks that it is better to plant in full light in the hope that the young widely-spaced plants on particularly favorable sites will be able to resist the insect by passing quickly through the susceptible stage.
Cater (1945), in Trinidad, considers that a 50 percent cover is better and that Cedrela plantations should be made on deep well-drained soils. Calcareous clay appears to give the best results. In addition, cover impedes growth of competing vegetation. He suggests planting on mounds, at 100 trees per hectare.
In countries where Latin-American Cedrela has been introduced, they have been similarly attacked. This is true in Ghana; in Nyasaland, however, they seem to have suffered less from this insect.
Cedrela toona and C. toona var. australis
Originating in Asia and Australia, these species are susceptible to attacks of Hypsipyla robusta in all countries where they have been planted. In Ceylon and India, it is recommended that Cedrela toona should not be planted on sites where Hypsipyla has occurred on other Meliaceae This precaution, which is considered more important even than soil and climatic conditions, thus limits the attacks. It is also recommended that close planting be done with persistent shade from above or wide planting with shade from the sides. It has been observed that the predators of Hypsipyla are found on the shading trees and other vegetation, bringing appreciable competition against the insect. In South India and in Ceylon, the insect does not occur on Cedrela toona or Swietenia at elevations above 1,600 meters. In Australia, research made on Cedrela toona var. australis points to a race which appears to be more resistant to Hypsipyla. Success has already been obtained with grafts of this variety of Cedrela toona.
Swietenia macrophylla, S. mahogani and other American Meliaceae
Although damage is common, the Philippines report that their plantations are still free from attack. In Malaya, also, damage is insignificant. Huguet and Marie (1951), in the French Antilles, indicate that attacks are associated with poor soil, excessive insolation and wind. They suggest that plants be protected by leaving brush to grow among the planted trees for lateral protection and to produce a mixed plantation on rich well-screened terrain. In Martinique, Hypsipyla also attacks Carapa procera, Cedrela odorata, Khaya senegalensis and Guarea trichiloïdes. The authors point out that the presence of Carapa permits the development and extension of Hypsipyla to Surinam and to Trinidad.
In Trinidad, it is reported that attacks are less strong than on Cedrela, and mixed plantations are recommended, as in Puerto Rico. The influence of shade is confirmed in a report of the Tropical Forest Experiment Station in Puerto Rico, which suggests that shade ought to reach 50 percent.
Swietenia plantations outside their native country are attacked equally, as in India for example. In Java, it is planted in mixture with other species. S. macrophylla is more resistant than S. mahogani.
Another of the Meliaceae, Carapa guianensis, is often attacked in Brazil.
Khaya and other African Meliaceae
Here also damage is common. Aubréville (1947) notes particularly the attacks on Khaya ivorensis, Entandrophragma cylindricum, and E. angolense in the Ivory Coast. He suggests favoring maximum growth of plants to escape the attack of the insect as rapidly as possible. In Nigeria, Butler (1952) reports that the attack is reduced when the plants receive lateral protection. He discovered that there is another borer, probably a Cerambycid which, in Ghana, attacks the young stems of isolated trees. It is advisable to use Sarcocephalus diderichii as a screen tree.
In the Belgian Congo, Khaya anthoteca is slightly attacked by a shootborer.
References
AUBRÉVILLE, A. Richesses permanentes de la Côte-d'Ivoire et du Cameroun. Agronomie Tropicale, Vol. II, No. 9/10, 1947.
BEARD, J. S. Summary of experiences with cedars (Cedrela mexicana) in Trinidad. Caribbean Forester, Vol. III, No, 3, 1942.
BEESON, C. F. C. Report by the Forest Department India, 1937-1938. Part I.
BELGIAN CONGO, I.N.E.A.C. Rapport annuel pour l'exercice, 1954.
BURGOS, JOSÉ A. Un estudio de la silvicultura de algunas especies forestales en Tingo Maria (Peru). Caribbean Forester, Vol. XI, No. 1/2 January/April 1954.
CATER, John C. The silviculture of Cedrela mexicana, Caribbean Forester, Vol. VI, No. 3, April 1945.
CHINTA, FELIX O. Trial planting of large leaf mahogany (Swietenia macrophylla). The Philippines Journal of Forestry, Vol. VI, No. 4, IVth Quarter 1949.
HARTIG, FRED. Informe sobre entomología forestal. FAO/ETAP No. 263, March 1954.
HOLDRIDGE, L. H. Comments on silviculture of Cedrela. Caribbean Forester Vol. IV, No. 1, January 1943.
HUGUET, LOUIS and MARIE, E.. Les plantations d'Acajou d'Amérique dans les Antilles françaises. Bois et Forêts des Tropiques, No. 17, 1st quarter 1951.
HUGUET, LOUIS and VERDUZCO, JOSÉ. Economia Forestal de Yucatán - FAO/53/3/1707, April 1952.
KAPUR, A. P. Rapport, sur les problèmes entomologiques des régions tropicales humides de l'Asie du Sud Unesco/NS/HT/50, 13 March 1956.
MARTORELL, LUIS F. A survey of the forest insects of Puerto Rico, Journal of Agriculture of the University of Puerto Rico. Vol. 24, No. 3/4, 1954.
NIGERIA, FOREST ADMINISTRATION. Use of Sarcocephalus diderichii as a nurse to Meliaceous - Report 1951/1952.
NIGERIA, VARIOUS AUTHORS. Correspondence. Vol. VI, No. 3 Nigeria July/Dec. 1945.
NOLTEE, A. C. Swietenia mahogani en Swietenia macrophyla Med. van het Proefstation voor het Boschvesen Buitenzorg. Java 1926, Tropical Woods No. 9, March 1927.
PARRY, M. S. Tree Planting Practices in Tropical Africa, FAO Forestry Development Paper No. 8, 1956.
QUEENSLAND, DIRECTOR OF FORESTS. Report 1955/1956.
UGANDA, FOREST DEPARTMENT. The Mahogany shoot borer (Hypsipyla albipartalis). Report of the Forest Department, Uganda, 1950.
