Factors Influencing Scale Insect Populations in Southern Pine Monocultures

Abstract

Pine seed orchards and Christmas tree farms in the southern United States have experienced rapid and severe scale insect population outbreaks during recent years. Though scale insect populations normally exist at low levels in such agroecosystems, certain conditions and management practices prevalent in monocultural systems are conducive to scale insect outbreaks. Presented, is a summary of research on factors that influence scale insect populations (i.e., weather, host plant, pesticide usage, and edaphic conditions), followed by a discussion of specific conditions and management practices in pine monoculture which affect scale insect populations. Primary consideration is given to: use of azinphos-methyl (Guthion) and fenvalerate (Pydrin) for control of seed cone insects and pine tip moths, which reduces populations of natural enemies attacking scale insects; affects of contiguous plantings of limited varieties of pine clones on both scale insect populations and scale parasitoid/predator diversity; and influence of fertilization on increasing scale insect numbers.