Bionomics of Platynota flavedana Clemens and P. idaeusalis (Walker)(Lepidoptera: Tortricidae) in Virginia apple orchards

The effects of pheromone trap placement on male moth catches of both species were studied. For P. flavedana, traps hung at 2.1 and 3.0 meters captured the greatest number of moths. Trap heights of 1.2, 2.1, and 3.0 meters caught the greatest number of P. idaeusalis moths. The outside-the-canopy trap position captured more P. flavedana moths, while the within-canopy trap location caught the greatest number of P. idaeusalis moths. Traps placed in the west portion of the tree captured the greatest number of P. flavedana moths. P. idaeusalis moth catches were not influenced by compass quadrants. Trap design and pheromone dispenser and rate influenced trap catches of P. flavedana.

Development of P. flavedana and P. idaeusalis on a meridic diet was observed at constant temperatures in the laboratory. Lower developmental threshold values for egg, larval, and pupal stages of P. flavedana were: 10.6, 8.6, 9.0°C, respectively. Lower developmental threshold values of 9.7, 7.0, and 8.5°C were estimated for P. idaeusalis egg, larval, and pupal stages, respectively. An average of 101.5 °D_10.6’, 379.6 °D_8.6’, and 126.0 °D_9.0’ were required for development of egg, larval, and pupal stages of P. flavedana, respectively. P. idaeusalis required 104.7 °D_9.7’, 442.7 °D_7.0’, and 132.2 °D_8.5’ to complete development in the egg, larval, and pupal stages, respectively. Differences in rate of development were observed between food sources for both species.

Within-tree spatial distribution of egg masses and fruit damage resulting from larval feeding for both species was investigated. P. flavedana egg masses were mostly found in the southern portion of the tree below 1.8 meters. Egg masses of P. idaeusalis were observed in greatest numbers in the southern and eastern quadrants of the tree below 2.8 meters. Fruit damage caused by larvae of both species was greatest in the lower portion of the tree. Wind dispersal of first-instar larvae between trees is believed to have influenced fruit damage distribution.

The seasonal activity of P. flavedana and P. idaeusalis was monitored. Degree-day accumulations for first moth catch, first and peak egg deposition, and first and peak egg hatch of both generations are presented.