ENHANCING PEST MANAGEMENT OF NEMATODES AND INSECT HERBIVORES THROUGH PLANT-MEDIATED EFFECTS

The goal of the proposed research is to understand how plant-mediated interactions between plant parasitic nematodes and insects influence pest and natural enemy attraction and foraging success. I will use a combination of field and laboratory experiments to determine what factors alter the outcomes of these interactions to create better pest management strategies that incorporate above- and belowground pests.1. Objective 1:determine how different types of fertilization influence nematode-insect interactions using a manipulative field experiment.To understand how fertilization treatments influence interactions between CPB and root-knot nematodes, I will perform a fully crossed experiment with three fertilization treatments and two levels each of CPB and nematode abundance. 120 Potato plants will be grown in pots in the greenhouse, equally divided between three fertilization treatments: minimal fertilization, organic industry standard, and synthetic industry standard. Three weeks after sprouting, half of the plants in each treatment will be inoculated with M. hapla; two weeks later, five 3rd-instar CPB will be added to half of the control plants and half of the plants inoculated with nematodesfor a total of 12 treatments with 10 replicates per treatment. At this point, all plants will be enclosed in mesh bags. Each week until pupation I will assess CPB survival. After pupation, I will subsample leaf tissue from five plants per treatment for LC/MS analysis of glycoalkaloid qualitative and quantitative changes. After adult CPB emergence I will measure survival to adulthood, number of root galls on plants with nematode inoculation, yield, and aboveground herbivory damage. The experiment will be performed twice for a total of 20 replicates per treatment and 10 LC/MS samples per treatment.2. Objective 2: Test how predator and entomopathogenic nematode attraction changes in the presence of nematodes in the lab.Plants for assays. To induce plant chemical response to herbivory, 120 potato plants will be grown in the greenhouse, half of which will be inoculated with root-knot nematodes at 3 weeks. Two weeks later, five 3rd-instar CPB will be added to 80 plants; 20 control plants and 20 plants with M. hapla will be kept insect-free. CPB will be allowed to feed for 5 days.Generalist predator Y-tube assay. In order to determine predator preference for the volatile profile of plants with different types and levels of nematode and insect herbivory, I will perform a choice assay with a generalist predator, Podisus maculiventris, and CPB larvae. After 5 days of feeding, I will remove CPB from 20 plants with nematodes and 20 plants without nematodes. One plant of each nematode treatment will be placed into a glass chamber and attached to a Y-tube olfactometer. One adult P. maculiventris will be released at the downwind entrance to the Y-tube and observed for 5 minutes or until it reaches ? of the way in one arm, which will be recorded as a choice. If it does not reach the end of one arm after 5 minutes, it will be recorded as 'no choice'.Belowground entomopathogenic nematode assay: I will use a 6-arm olfactometer to test the attraction of entomopathogenic nematode H. bacteriophora to plants with different combinations of nematode and insect damage using established methods. For each replicate (20 total) I will use plants with four damage treatments: CPB and M. hapla damage, CPB damage only, M. hapla damage only, and no damage. H. bacteriophora will be added to the central chamber and allowed to disperse for 8h, at which point arms will be detached from the setup and the number of H. bacteriophora will be extracted using Baermann funnels and counted. If H. bacteriophora shows a preference for certain treatments, I will collect belowground volatiles from 5 plants of each treatment and analyze them on a GC/MS using established methods.