Alterações de componentes silviculturais e de produção de Hevea brasiliensis causados por Meloidogyne exigua

Abstract

Natural rubber production, from latex extracted from rubber trees (Hevea brasiliensis), is an essential activity for national economy. The major yield limiting factor is disease occurrence. Meloidogyne exigua, the root knot nematode, is the etiological agent of the main root disease of this species in Brazil. Its early identification in a rubber tree orchard allows better management, reducing potential damages and losses. This study determined damages and losses caused by this nematode to rubber tree crop. The area used for this study was planted with 500 trees per hectare, is ten years old, tapping begun when they were seven years old, and it is located in the Triângulo Mineiro (MG). The area was selected based on two distinct infestation levels (low or high) by the root knot nematode in the rubber tree rootlets. Silvicultural characteristics, such as stem circumference (cm) and basal area (m2 ha-1), as well as survival (%), amount and size of rubber trees under tapping (circumference > 0.45 m), or not being tapped (circumference < 0.45 m), were compared and correlated (Pearson’s) among each other and with infestation levels. Latex production in each infestation level was used to estimate losses caused by heavy infestation of the root knot nematode. Characteristics such as survival, number of trees under tapping, trees with CBH greater than 45 cm and basal area were drastically reduced, while the number of trees taken out of tapping and with CBH smaller than 45 cm increased in areas with heavy infestation. In contrast, all characteristics evaluated presented favorable results when nematode infestation level was low. However, since this is a perennial crop, the activity may become unsustainable in the near future. Latex production in the low infestation area, between 10.4 and 11.5 lower than the high infestation one, is, respectively, 153% to 264% greater than that in the high infestation area