The impact and production of the Brazilian peppertree biological control agent Pseudophilothrips ichini (Thysanoptera: Phlaeothripidae) is affected by the level of host-plant fertilization

Abstract

Brazilian peppertree, Schinus terebinthifolia Raddi (Anacardiaceae) is an invasive weed of natural and agricultural areas of Florida, Hawaii, and Texas (USA). A thrips, Pseudophilothrips ichini (Hood) is being developed as a potential agent for biological control of this invasive weed. As field releases are planned, methods are needed for the mass production and to predict the impact of the thrips. Brazilian peppertree seedlings were grown in potting media amended with three fertilizer (24N-8P-16K) levels: low (0 g/l water), medium (1.8 g/l water) or high (3.6 g/l water). The greatest number of P. ichini thrips developed on the medium fertilized plants. To measure P. ichini thrips impact, we compared growth of these fertilized seedlings with or without thrips. While maintaining the number of P. ichini thrips adults constant (20 adults), we measured the impact of one or two generations of feeding. Fertilizer level had a significant effect on all plant responses. Both one and two generations of thrips significantly decreased plant height, number of branches, leaflets, leaves, and tips. Two generations of thrips feeding caused significant reductions in branch, leaf, and total biomass. Thrips feeding increased percent nitrogen in roots and decreased percent nitrogen in branches at the medium and high fertilizer levels. Percent nitrogen of field collected stems and leaves matched that of the low fertilizer level. These results suggest a medium fertilizer application is best for mass production of P. ichini thrips. Moreover, sustained damage for more than one generation of thrips feeding will have a significant impact on total biomass of S. terebinthifolia seedlings. The use of fertilized nursery sites may help in initial establishment and field mass production of P. ichini thrips.