Fertilization increases Hylobius abietis L. damage in Pinus pinaster Ait. seedlings.

摘要

Maritime pine (Pinus pinaster) is the most important forest tree species in Galicia (NW Spain), and the pine weevil (Hylobius abietis) can be a serious problem to its regeneration. Fertilizer application is a commonly recommended silvicultural tool for P. pinaster, especially in second rotation reforestations where large amounts of nutrients may be extracted through harvesting. But increased nutrient availability could promote undesired side-effect on host resistance and pest damage. We studied the effect of fertilizer application on pine growth and weevil damage during two growth periods after planting in a P. pinaster progeny x fertilizer application trial with nine treatments (control and 8 combinations of ammonium nitrate, calcium phosphate, potassium sulfate and magnesium sulfate). Both factors, fertilizer application and family, had a strong and significant effect on growth and pine weevil damage. The damage by the pine weevil was greater in amended plants (debarked area score up to 2.9-fold greater) than in the unamended control, inducing a 3.7-fold greater leader loss in the former. The damage was lower when calcium phosphate was absent than when it was present, averaging approximately 2- and 2.7-fold above the unamended control, respectively. In spite of the attack, 1 year after planting, fertilizer application significantly increased diameter and height in plants that were able to maintain the leaders alive, averaging approximately 1.2-fold above the control. But when the height of the whole plantation was considered (actual height), amended plants did not differ from the unamended ones. Moreover, the attack of H. abietis during the first growing period affected subsequent growth, resulting in no significant effect of fertilizer application on growth at the end of the second growing period. Attack by H. abietis caused the loss of the growth benefits promoted by the fertilizer application input..