Orchard Age Research Articles

Community Structure of Phytophagous Arthropods on Apple

The phytophagous arthropod community on apple was studied in Virginia, West Virginia, Pennsylvania, and New York in 1983 and 1984. Managed, “organic” (reduced management), and abandoned orchards were sampled and the arthropod communities therein were compared to examine the effects of orchard management on the community. Williams's index, species richness, and evenness all showed significantly greatest diversity in abandoned orchards, intermediate diversity in “organic” orchards, and least diversity in managed orchards. Diversity in the “organic” orchard decreased during the 2 yr of study, showing the cumulative effect of orchard management on the system. Similarity among orchards, within management class, ranged from 28 to 60%. Percentage of similarity and diversity indices indicated that cultivar and orchard age differences were not significant factors in comparisons among orchards. Communities were dominated by r-selected species in managed orchards and K-selected species in abandoned orchards. Community structure is hypothesized to be regulated by human-induced, environmental factors in managed orchards and by natural enemies in abandoned orchards.

Marginal analysis and cost effectiveness in seed orchard management

We use marginal analysis for three seed orchard management decisions. First we consider the roguing of a seed orchard established with many untested trees. We show that inferior parents should be rogued to the point where the number of orchard trees times the average expected volume gain of trees from seed produced by that orchard is maximized. Marginal analysis also is useful where one must choose the number of trees to establish in an orchard planted after progeny tests have identified superior parents. The cost of establishing many ramets to meet early seed production goals can be balanced with the projected value of seed. For the example presented, an additional orchard tree is cost effective if its seed is needed at an orchard age of 12 to 15 years. Finally, we use marginal analysis to determine whether to induce a seed orchard to increase its seed production when there is an excess demand for seed. This decision is guided by balancing the cost of the induction treatment with the combined effect of expected increase in seed harvest, the amount of genetic gain, and the discount rate. We present a four-quadrant decision diagram for estimating this balance. In designing tree improvement programs, these analytical techniques can be applied to proposed alternatives as one way to structure decision making and to provide comparable economic assessments from which cost-effective choices can be made.