First report of Hypsipyla grandella ( Lepidoptera : Pyralidae ) on African mahogany

The mahogany shoot borer Hypsipyla grandella Zeller is an important economic pest in all American tropical forests, because it prevents monoculture of valuable timber trees species like mahogany and cedar. The shoot borer damages several tree structures, especially the apical shoots, impairing the formation of the commercial stem. This pest can attack the plants during the year and one larva per plant is enough to cause significant damage. In infested areas, the attack can reach up to 100 % of the trees. The Australian cedar and African mahogany have been cultivated in Brazil for timber production, because they are considered resistant to H. grandella (Lepidoptera: Pyralidae) attack. However, in this work we report for the first time the H. grandella attack to African mahogany Khaya ivorensis.


Introduction
The forest species of Meliaceae family, native to Tropical America, is largely explored due to the high commercial value of its timber.In Brazil, there are six genera and about 100 species, highlighting Carapa, Cedrela and Swietenia.However, mahogany monoculture, along with other American Meliaceae, is impaired due to mahogany shoot borer Hypsipyla grandella (Zeller) attack (Lunz et al., 2009;Paul and Weber, 2013).This shoot borer is a Lepidopteran that co-evolved with some Meliaceae species.It attacks preferably Swietenia, Cedrela and Carapa (Navarro and Hernández, 2004).
Mahogany shoot borer occurs in South America (except Chile), Central America and South Florida and it follows the Meliaceae distribution pattern of which they feed (Griffiths, 2001;Horak, 2000).This borer may attack several plant structures and its main damage involves the perforation of young branches, especially the apical shoot, causing tree bifurcation, significantly reducing the economic value of the timber.This results in the reduction of plant growth and timber production (Newton et al., 1993(Newton et al., , 1999)).The attacks are frequent since the initial phases of plant development, when the plants are more susceptible to infestation (Ennion, 2003).Attacks can reach 70 % of the plants in the first 12 months after planting and up to 100 % at 24 months (Paul and Weber, 2013).This prevents the monoculture establishment of native Meliaceae.
The monoculture of exotic species like Khaya spp.and Toona ciliata M. Roem in Brazil poses as an alternative to native Meliaceae for being resistant to H. grandella (Lunz et al., 2009;Perez et al., 2010), due to absence of co-evolution of these species (Agostinho et al., 1994).It is estimated that there are 400 producers that cultivate about 15 thousand hectares of Khaya ivorensis A. Chev., in the states of Minas Gerais, Pará, Mato Grosso, Goiás and Paraná.African Mahogany has been on the market in the United States of America for a long time, but its use dramatically increased after 2003 when Swietenia macrophylla King was listed in CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora).Currently, K. invorensis is the species of the African mahogany most important in the international market (Stephens, 2010).Then, this work aimed to report the H. grandella attack to African mahogany Khaya ivorensis.

Materials and Methods
In June 2015, apical shoots of Khaya ivorensis were detected with holes, feces and exudations, characteristic of mahogany shoot borer, on a commercial crop of 25 ha, in Patos de Minas, Minas Gerais state, Brazil (18°34'44" S, 46°31'05" W, 824 m above sea level).The plants were 3 years old and 3 % of them were attacked.The region is under the Cerrado domain and has plain relief.The predominant soil is the Oxisol.The climate is tropical with dry season.The average annual temperature is 22.8 °C and average annual rainfall is 1445 mm.

Results and Discussion
Six pupae were formed, four which were female, with two presenting atrophied wings.H. grandella larvae feed on leaves of Khaya senegalensis (Desr.) A. Juss. in laboratory conditions, but the adults emerge with abnormal wings and affected reproductive performance (Perez et al., 2010).The taxonomist Victor O. Becker (Uiraçu Institute, Camacan, BA) identified the adults as Hypsipyla Khaya ivorensis Note Sci.Agric.v.74, n.6, p.492-494, November/December 2017 grandella using Heinrich illustrations (Heinrich, 1956) and by comparison with species voucher of Becker Collection.This is the first report of H. grandella attacking K. ivorensis in Brazil.
In spite of the incentives for planting exotic species of Meliaceae as an escape strategy to H. grandella attack, in order to meet the high demand for hardwood, this report puts on alert all producers of these crops.This pest is present in the field throughout the year (Taveras et al., 2004) and is a constant threat in the first years after planting (Wightman, 2008) when the plants are more susceptible (Ennion, 2003).Once the plantation is invaded by insects, almost all trees are damaged (Paul and Weber, 2013), and the damage threshold corresponds to one caterpillar per plant (Hilje and Cornelius, 2001).Brazil has the largest natural reserve of tropical native mahogany (Swietenia macrophylla), which is the main host of H. grandella.Thus, the shoot borer is present in almost all regions where Khaya sp. and Toona ciliata are cultivated.
Few control strategies have been studied; however, no efficient control measures for mahogany shoot borer have been achieved (Lunz et al., 2009).Studies have pointed out that some culture practices may reduce the damages such as pruning the affected branches and lateral shading (Hilje and Cornelius, 2001;Opuni-Frimpong et al., 2008); mosaic planting with other arboreal species such as Cassia siamea Lam., Eucalyptus spp.(Hilje and Cornelius, 2001) and other shrubby crop species (Paul and Weber, 2013); avoidance of shallow soils, with high acidity and deficient drainage (Hilje and Cornelius, 2001).
Very likely, the increase in the selection pressure, exerted by extensive resistant monocultures may contribute to the reduction of resistance of Khaya ivorensis by H. grandella, because this pest has the ability to attack this plant.This fact has been reported in Hypsipyla robusta attacking the American mahogany Switenia macrophyla cultivated in Africa and Australia (Newton et al., 1993;Cunningham et al., 2005), Diabrotica virgifera virgifera LeConte migrating from corn to soybean (Meloche and Hermans, 2004), and Euschistus heros migrating from soybean to cotton (Azambuja et al., 2013).Further research must be encouraged concerning monitoring, pest control techniques, selection of new resistant materials and resistance management strategies, such as the use of structured refuge with susceptible materials.