The Utility of Silicate Fertilizers in an Integrated Pest Management Program; Increasing Plant Health to Improve Pest Management

With increasing regulation of pesticide use and a growing number of independent sustainable agricultural certification services fueled by the general public's desire for less pesticides, alternative pest management strategies are needed. It is well known that nutrient management can influence pest populations. Silicon and its impact on plant health has been studied extensively in some cropping systems and has been attributed to improved disease resistance, improved response to drought stress and salt stress, increased structural stability and negative effects on herbivore populations. However plants vary widely in the total amount of silicon that they are able to accumulate. This variation in accumulation may in part account for the diverse results observed in different herbivore/plant systems. Very few studies however have looked at silicon's impact on herbivores of dicotyledonous plants as monocotyledonous plants tend to accumulate silicon at a higher rate. In addition the literature on silicon's utility in horticultural cropping systems for arthropod pest control is almost nonexistent. This dissertation focuses on the use of potassium silicate as an integrated pest management tactic in horticultural production. Chrysanthemum and its primary pest Liriomyza trifolii (Burgess) (Diptera; Agromyzidae) served as the model system used for most of this work. Changes in the plant induced by silicon supplementation such as leaf toughness, photosynthetic metrics, leaf volatile signatures and leaf surface features were assessed. Leaf toughness and photosynthetic metrics seem to be unaffected by silicon supplementation, however several volatile compounds were isolated that seem to be effected by silicon supplementation. Trichome length was increased by silicon supplementation. In addition greenhouse studies showed that L. trifolii populations can be reduced by silicon supplementation. Possible mechanisms and implications for management decisions are discussed.