The Effect of Leaf-Mining by Liriomyza Trifolii on Seed Set in Greenhouse Marigolds

The effect of foliage feeding by the serpentine leafminer, Liriomyza trifolii (Burgess), on seed production and germination by male-sterile marigolds (Tagetes erecta L.) was examined over two cropping seasons in commercial production greenhouses. Five components of T. erecta relative fitness (the number of flowers, ovules, and germinations per plant, seed mass, and plant height) were compared in plants grown under four different control strategies representing three different intensities of L. trifolii herbivory: no control (high herbivory), biological or chemical control (intermediate herbivory), and insect-free (low herbivory). In both years of the study, significant between-treatment differences in number of viable seeds per plant were detected but no significant differences were found in the other four relative fitness measures. The number of viable seeds was highest with high herbivory (no-control treatments) and lowest with comparatively low herbivory (chemical and insect-free treatments). L. trifolii damage may reduce photosynthate availability, which may slow seed development and increase the length of time in which ovule physiological and morphological conditions are suitable for successful fertilization. Because all plants within each year received an equal number of pollinations occurring at the same time relative to plant growth, ovules within plants in the high-damage treatments may have had a greater probability of being fertilized, resulting in an increase in production of viable seeds.