Ctenarytaina spatulata, Taylor: soil water, mineral nutrients and their relations to eucalyptus dieback

Abstract

To develop this study it was used Eucalyptus grandis seedlings planted in three-liter pots, filled with soil collected on areas where dieback occurred (Arapoti, PR). The experiment consisted of six soil water level treatments, with and without insects. The experimental design was randomized blocks with 6 replications, arranged in six cages inside a green house. Three cages received insects and other three, not. The experiment consisted of the following treatments: 1. Sat. - soil water content maintained on the saturated conditions; 2. CC - soil water content maintained on field capacity; 3. 60 - humidity of the soil to 60% of the field capacity; 4. 30 - humidity of the soil to 30% of the field capacity; 5. A7 - soil water content maintained 7 days on the saturated condition and 7 days on 60% of the field capacity; 6. A15 - being 15 days in the saturation point and 15 days 30%da field capacity. The biomass accumulation (leaf, stem, branches and total), increased with the increase of the water supply on the soil. Same behavior was observed for the insect population. Plants infested with Ctenarytaina spatulata Taylor, 1997 presented a smaller biomass accumulation on average, except for the treatment with water stress alternation. The largest seedling growth and leaf production induced the dilution effect of some nutrients. The water stress, decreasing water supply did not enhance the C. spatulata Taylor, 1997 population growth. Even on presence of large N contents, due to the nutrient concentration effect for the smallest growth, possibly there was a decrease of the amount of appropriate insect food.