Infestation and damages of Cinara atlantica due to nutritional status and to water stress on Pinus taeda L. seedlings

Abstract

The response of Cinara atlantica population to the nutritional status of recently planted seedlings of P. taeda was evaluated on field, in Três Barras city in the state of Santa Catarina, and to water stress in greenhouse, in Colombo city, Paraná state. In the greenhouse, 4 treatments were tested with 30 plants each treatment: non-stressed seedlings (at 60% of field capacity) and the stressed ones (at only 30% of field capacity), with and without insects. Each plant was infested with 10 nymphs of 3^rd and 4^th instars. Weekly, the number of aphids was counted, the height and diameter of the plants were measured, the nutritional status of the needles were analyzed and the volume of water applied accordingly. It was observed that the recently-planted seedlings were less attractive to C. atlantica because of their low N content condition caused by planting stress. The infestation of the water stressed plants in the greenhouse was the double of the population on the non-stressed plants. Plant height increased directly proportional to the aphid infestation and the impact of the insects was equivalent to that resulting from the water stress. The infested seedlings also presented an increasing in diameter, but there was no influence of water stress.