Determination of the harm of Sagalassa valida Walker (Lepidoptera: Glyphipterigidae) in the root system of the oil palm
The harm of the root borer S. valida has been unperceived. The reason for this is that the evaluations have been directed towards palms younger than 3 or 4 years and to the percentage of primary roots with fresh S. valida harm, in which the harm and the presence of the plague in larva stage is more evident. Nevertheless, there is no information on the distribution of the insect according to: the age of the palm and the damage on secondary and tertiary roots as well as absorbent hairs. This circumstance has originated misunderstandings in the appreciation of the damage and in the evaluation of the real incidence of the plague. To determine the damage in the radical system caused by S. valida in 6 to 10 years old sowing palms, 10 apparently healthy palms and 10 symptomatic palms, for each age, were selected. The palms affected by the borer were chosen having in minded the external characteristics such as delay in growth, foliage yellowness, presence of more than 10 masculine inflorescences, and absence of feminine structures. The apparently healthy palms were chosen having in mind that they presented good foliage, more than 10 feminine inflorescences, and absence of masculine inflorescences. Soil samples of a diameter of 10 cm. were taken at 0, 0.5, 1.0, 1.5 and 2.0 m from the base of the palm, and at three depths: 20, 40, and 60 cm for a total of 15 samples per palm. The samples were processed with the help of a hydraulic root washer. From each sample the primary, secondary, tertiary and quaternary roots were extracted. The number of roots, weight, and the percentage of damage caused by S. valida to the primary roots were registered. The roots were dried at 105°C during 24 hours and then were weighed. When the dry weight of the primary roots was analyzed, it was observed that it diminishes as it gets further from the trunk and as the depth grows. It is important to note that in all sites, the weight of the roots of healthy palms was greater compared with the palms affected with S. valida. If it is assumed that the radical system of the apparently healthy palms was ideal and it was compared with the root system of palms attacked by the insect, there would be a very high loss of roots in the two ages of the palm which were evaluated. The percentage of loss of primary root between 0 and 20 cm depth would be stronger at 1.5 m of distance from the trunk in 6 years oil palms, while for the 10 years old palms would be between 1 and 1.5 m from the trunk.
| Main Authors: | , , |
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| Format: | Digital revista |
| Language: | spa |
| Published: |
Fedepalma
2000
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| Online Access: | https://publicaciones.fedepalma.org/index.php/palmas/article/view/780 |
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