EFFECTS OF ENVIRONMENTAL HETEROGENEITY ON LEPIDOPTERA AND HYMENOPTERAPOPULATIONS IN EUCALYPTUS PLANTATIONS IN BRAZIL

For 5 months, insects from the Lepidoptera and Hymenoptera orders were collected at five sites: in the interior of a Brazilian native forest , in the zone of contact between the native forest and a Eucalyptus pl antation, and in three sites within the Eucalyptus plantation, at 200, 400 and 600 m from the edge of the native forest. Lepidoptera were co llected with light traps and divided into three groups in relation to the damage they cause to Eucalyptus: primary pests, secondary pests, a nd other abundant but non-pest species. Hymenoptera were collected wit h Malaise traps and categorized as predators, egg parasitoids or larva l parasitoids, In general, the heterogeneity hypothesis was supported: total lepidopteran abundance was higher and total natural enemy abund ance was lower in the Eucalyptus plantation than within the native for est or at the edge of the native forest and the Eucalyptus plantation. Negative correlations were found between the abundance of Lepidoptera and that of egg parasitoids and larval parasitoids. No significant di fferences in the abundance of lepidopteran pests and hymenopteran natu ral enemies were found among the three sites within the Eucalyptus pla ntation. Plantations of Eucalyptus intercalated with native vegetation could reduce outbreaks of lepidopteran pests by increasing numbers of Hymenoptera natural enemies of these pests. (C) 1998 Elsevier Science B.V.