The effects of potassium silicate fertilizer on citrus leafminer, Phyllocnistis citrella, oviposition preference

Soluble silicate fertilizers have the potential to be a valuable pest management tool in California nursery trade. These solutions are easily utilized via irrigation and pose minimal health risks to workers and the public. Several studies show that silicates reduce the availability and quality of food for insect herbivores, resulting in reduced insect growth and reproduction. Our current research seeks optimal application methods for silicate fertilizers to reduce Phyllocnistis citrella, the citrus leafminer (CLM) populations.

CLM causes significant economic damage in nursery citrus plants. Our preliminary studies show a significant reduction in leaf damage on young citrus nursery stock following treatment with potassium silicate. Whether this was due to CLM adult avoidance of oviposition on treated plants, or CLM larval inability to feed on treated plant tissue is unknown.

A three-part choice test determines adult CLM preference for silicate treated vs. non-treated citrus leaves as oviposition substrate. Treatments include treated X non-treated; non-treated X non-treated; treated X treated. Unexpanded leaves of 'Bouquet de Fleurs' sour orange serve as test material, because they are particularly susceptible to CLM attack and are an important ornamental citrus crop in California. All plants are grown in coir media (which has little to no available silicates) and treated plants receive potassium silicate (K₂SiO₃) solution with irrigation. Male and female CLM moths are released into cages with plants 1-2 days after eclosion. Adults are removed after 48 hours. Larval leaf damage is assessed after 2 weeks using imaging software.