Nutrient-rich river diversions into Louisiana wetlands aim to restore areas threatened by saline conditions. To investigate how nutrient additions and host genetics affect insect performance, we subjected five half-sibling genotypes of baldcypress to control, low, and high levels of fertilization over two growing seasons. Larval relative growth rates and dry pupal weights were recorded and tree diameter growth, height growth, foliar N, P, K, phenolics, moisture, length and width measured. We found no significant interactions between genotype and fertilization, suggesting the baldcypress leafroller will respond predictably across nutrient regimes, irrespective of intraspecific host variation. Larvae reared on genotypes in the low fertilization displayed significantly higher dry pupal weights than those reared on genotypes in the control fertilization. Foliage samples from trees in the low fertilization were significantly higher in nitrogen and potassium, numerically higher in moisture content, and contained significantly lower total phenolics. Genetic variation among genotypes in one study was a significant factor. Both males and females displayed significantly lower dry pupal weights when reared on genotypes fa7 and sg2 than on cb3, sw2, and ve2. Genotypes fa7 and sg2 contained significantly lower foliar nitrogen, significantly higher total phenolics, and though not significant, longer leaves and lower leaf moisture. This evidence suggests stands of baldcypress may respond positively to nutrient additions, and may increase leafroller size, hence, leading to potentially higher populations. However, phenotypic variation in budburst among genotypes should not be overlooked as a significant factor affecting leafroller performance.
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