Plant defense induction and antogonism at the field

Plants have evolved many constitutive and inducible defensive mechanisms to help deter pathogen or herbivore attack. These defensive mechanisms are induced through foliar applications of plant hormones, such as methyl jasmonate (MJ) and methyl salicylate (MS). In high tunnel conditions we tested H1: Elicitors will reduce aphid density in tomato and pepper plants and H2: Elicitors will improve yield in the presence of pests. Treatments included MJ, MS, Botanigard (B), MJ+B, MS+B, and Control (C). Variables studied were aphid density and fruit yield. Tomato crops resulted with a low aphid infestation in both 2007 and 2008. In 2008, pepper plants harbored a significantly higher aphid density than tomato plants (P < 0.03). Overall, tomato yield accumulation in both years were not significantly different among the treatments, even though B and C had significantly higher yields than MJ+B and MJ treatments in one of the collection dates. The differences were not significant 9 of the 10 collection days and therefore, we conclude no treatment effects on tomato yield. In 2008, treatments did not induce pepper plant defense and under higher infestation treatments did not improve yield. In tomato, B induced plant defense and worked as a synergist. We found that elicitors did not affect crop yield under low and high pest infestations in both tomato and pepper. This study shows that crop species plays an important role on plant defense and aphid density in an agricultural system using elicitors.