A comparison of field population dynamics in relation to developmental time and fecundity under laboratory conditions of the foliage aphid species complex on pecan

Abstract

Field and laboratory studies conducted at College Station, Texas from 1974 to 1976 were concerned with population dynamics of foliar pecan aphids and several biological features. Principle areas of investigation include field population dynamics, entomophagous arthropods, life cycle duration, survival, fecundity, adult longevity, and population increase at various constant temperatures. Three species of aphids were feeding on the pecan leaves, the yellow aphid complex, the blackmargined aphids Monelia caryella (Fitch) and Monelliopsis nigropunctata (Granovsky), and the black pecan aphid Tinocallis caryaefoliae (Davis). Yellow aphids reached highest populations at mid to late summer, while black aphids peaked at late summer and early fall. Several predators fed on the pecan aphids. Only Aphelinus perpalidus (Gahan) parasitized yellow aphids, while an entomophagous fungus Entomophtora sp. killed all three species of aphids. Developmental time was shorter for the blackmargined aphid (9.0, 6.9, and 6.0 days) than for the black pecan aphid (12.2, 8.8, and 7.5 days) and 20 degrees Celsius, 25 degrees Celsius, and 30 degrees Celsius respectively. Highest offspring mortality was experienced during the first instar. Higher temperatures favored the blackmargined aphid survival while low temperatures favored that of the black pecan aphid. Fecundity of the black margined aphid was from zero to 164 with mean values from 17.6 to 73.6 offspring per female. More offspring were produced at 25 degrees Celsius and less at 30 degrees Celsius. Fecundity of the black pecan aphid was from zero to 174 with mean values ranging from 26.6 to 74.9 nymphs per female. Highest fecundity was recorded at 20 degrees Celsius and 25 degrees Celsius and lowest at 30 degrees Celsius. Adult longevity was up to 50 days for the blackmargined aphid and longer survival was observed at 25 degrees Celsius. Adult black pecan aphids were living up to 39 days; longer survival was achieved at 20 degrees Celsius and 25 degrees Celsius...