Common Name: Blackmargined aphids
Scientific Name: Monellia caryella (Fitch)
Description: Both species are clear to yellow or pale green aphids that grow to be about 1/16 inch long. Adults can be identified to species because those of the blackmargined aphid, Monellia caryella (Fitch), have a black front margin on their forewings and hold their wings flat over the back of the body. The yellow pecan aphid, Monelliopsis pecanis Bissel, has clear wings which are held roof-like over the back of the body. Immature stages (nymphs) are wingless and appear solid yellow.
The black pecan aphid, Melanocallis caryaefoliae (Davis), also occurs on pecan. It is a more solitary species, and most infested leaves will have only a few aphids. However, the aphid injects a toxic salivary secretion into the feeding site and as a result, entire portions of the leaves between major leaf veins turn yellow (yellow areas appear rectangular or quadrilateral) and ultimately brown. Heavily injured leaves drop prematurely, which can negatively affect the current and following year’s pecan production. The biology of this aphid is similar to the yellow pecan and blackmargined aphids.
Life Cycle: Simple metamorphosis; parthenogenic. The life cycle of these species is similar. Winter is spent in the egg stage in bark crevices and under loose bark. Wingless nymphs hatch in the spring after leaves develop and mostly move to the undersurface of leaves where they feed and develop through four stages (instars) over about 6 days. Winged and wingless adults that develop produce more young aphid nymphs without mating (through a process called parthenogenesis). Each adult can give birth to about 125 aphid nymphs over 18 to 33 days! Many (16 to 32) generations occur annually. When cooler weather arrives, eggs are produced for the winter.
Habitat and Food Source(s): These aphids occur on pecans. Adults and nymphs remove sap from the leaves. Heavily infested trees have leaves that become coated with a sticky sugary film called “honeydew.” This energy-rich layer supports the development of a fungus called sooty mold. This black layer on leaves reduces the leaves ability for photosynthesis. Severely infested trees prematurely drop their leaves. Although sap loss may affect the crop of pecans being produced during the season, the loss of
Pest Status, Damage: Can build up in large numbers resulting in an accumulation of sticky “honeydew” on surfaces underneath the infestation on which the black sooty mold fungus develops; medically harmless.
Management: See Aphids in Texas Landscapes.
Literature: Boethel & Bagnet; Tedders 1978.