IntercroppingCedrela odoratawith Shrubby Crop Species to Reduce Infestation withHypsipyla grandellaand Improve the Quality of Timber

Abstract

Cultivation of Cedrela odorata, a valuable tropical hardwood species, is restricted by the mahogany shoot borer (Hypsipyla grandella), whose attacks reduce stem quality in forest plantations. is study investigated whether infestation rates would be reduced and growth performance improved by the intercropping of C. odorata tree seedlings with different crop rotations. e height increment achieved by C. odorata during the �rst two years was signi�cantly stimulated by the intercropping of maize (Zea mays), pigeon pea (Cajanus cajan), and cassava (Manihot esculenta). Attacks of H. grandella were also considerably reduced in these treatments, compared to the control plots, while intercropping with beans and rice produced no improvement. e effect was particularly distinct when lateral competition between trees and crops was high. Accordingly stem quality was higher in the treatments featuring tall crops. Trees intercropped with C. cajan performed best in terms of height (276 cm ±93), survival (100% ±0), and quality (81% ±13.5 of trees with satisfying stem quality) aer two years. We concluded that intercropping of tree seedlings which are susceptible to H. grandella with shrubby multipurpose species can improve both tree growth and timber quality and hence increase the attractiveness of such species for reforestation.

Between land sharing and land sparing – what role remains for forest management and conservation?

“…For instance, the intercropping of trees with crops during the first years of forest stand establishment can increase the economic attractiveness of afforestation, as crops generate early returns while at the same time providing food resources (Paul et al 2015). Paul and Weber (2013) demonstrated in Panama that damages from Hypsipylla grandella to Cedrela odorata were significantly reduced when planted in a timber-based agroforestry system. This finding is of high importance, as this pest is a great impediment to afforestation with this valuable and endangered tree species.…”

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

“…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.…”

“…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). …”

“…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.…”

“…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.…”