Distribution of Darna trima (Moore) and D. bradleyi Holloway Larvae (Lepidoptera : Limacodidae) in oil palm canopy, in a single species and a double species infestations. - (:unkn) unknown
In a field study in Malaysia with oil palms, where the larval density of Darna trima was highest in the fronds located in the middle of the canopy (frond 20), the relationship between density of larvae and frond number was described by y 33.8 + 19.2x - 0.48x2 (r20.75, P0.001). The larval densities of the distal and middle sections of a frond were more than twice that of the proximal section (all sections had equal number of pinnae). Where the infestation was predominantly by D. trima and D. bradleyi, the larval density of D. trima was related to frond number by the equation, y -27 + 194x - 12.8x2 - 0.21x3 (r20.96, P0.001), and which peaked in frond 9. There was no significant difference between the number of larvae on the left (446 70) and right (422 110) side of the fronds. However, the distal and middle sections had respectively five and eight times more larvae than the proximal section. For D. bradleyi, the relationship between larval density and frond number was described by y 24.6 - 1.61x + 0.22x2 (r20.80, P0.001). No significant difference was recorded between the right (101 65) and left (46 54) side of the frond, although significantly more larvae (5 times more) were found on the middle section of the frond than on theproximal section. The results suggested that for a reasonable pre- or post- treatment census of D. trima, fronds 15-25 may be used in the single species infestation, while fronds 7-11 may be sampled in a double species infestation. This takes into consideration other factors such as age of palm, level of damage, larval density level and number of fronds on the palms. Furthermore, the number of larvae on one side of a frond can be used to estimate the total number of larvae present per frond, although the larval density may vary along the length of the frond.
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In a field study in Malaysia with oil palms, where the larval density of Darna trima was highest in the fronds located in the middle of the canopy (frond 20), the relationship between density of larvae and frond number was described by y 33.8 + 19.2x - 0.48x2 (r20.75, P0.001). The larval densities of the distal and middle sections of a frond were more than twice that of the proximal section (all sections had equal number of pinnae). Where the infestation was predominantly by D. trima and D. bradleyi, the larval density of D. trima was related to frond number by the equation, y -27 + 194x - 12.8x2 - 0.21x3 (r20.96, P0.001), and which peaked in frond 9. There was no significant difference between the number of larvae on the left (446 70) and right (422 110) side of the fronds. However, the distal and middle sections had respectively five and eight times more larvae than the proximal section. For D. bradleyi, the relationship between larval density and frond number was described by y 24.6 - 1.61x + 0.22x2 (r20.80, P0.001). No significant difference was recorded between the right (101 65) and left (46 54) side of the frond, although significantly more larvae (5 times more) were found on the middle section of the frond than on theproximal section. The results suggested that for a reasonable pre- or post- treatment census of D. trima, fronds 15-25 may be used in the single species infestation, while fronds 7-11 may be sampled in a double species infestation. This takes into consideration other factors such as age of palm, level of damage, larval density level and number of fronds on the palms. Furthermore, the number of larvae on one side of a frond can be used to estimate the total number of larvae present per frond, although the larval density may vary along the length of the frond.
Keywords: Darna; Insectos dañinos.; Poblaciones; Insectos defoliadores.; Palma de aceite