Aphids or “plant lice” are soft bodied pear-shaped insects generally less than 1/8 inch long. Their color varies according to species, however the common ones are usually green, yellow or black. The most distinguishing feature in the identification of aphids is the two short cornicles or tubes which extend from the end of their body. These structures are partly responsible for secretions of a fluid thought to be useful as a defense mechanism.
Most aphids, even adults, are wingless but when colonies become overcrowded or the host plant becomes undesirable, winged forms are produced and these establish new colonies. An exception to this are adult crapemyrtle aphids which are all winged. Temperature and photoperiod also affect the production of winged and wingless forms. Aphids are unlike most insects in two ways:
Aphids have the ability to reproduce rapidly and there are many generations per year. Each female aphid produces 50 to 100 daughters during her life span, and each daughter can begin reproducing in six to eight days.
Aphids have piercing-sucking mouthparts and cause damage by sucking the plant juices. They are commonly found on the stems, undersides of leaves and on flower buds in colonies of individuals. However, their ability to transmit plant virus diseases may be more harmful than any direct feeding damage.
Aphids seem to be especially troublesome on plants that are in shaded areas. Their feeding causes the leaves to curl or crinkle and flower buds may become hardened causing the flowers to be distorted.
Aphids excrete large amounts of honeydew which is a sugary liquid composed of unused plant sap and waste products. This provides an excellent medium for the growth of a black fungus called “sooty mold”. Besides being unattractive, sooty mold interferes with photosynthesis and somewhat retards the growth of the plant. Sooty mold usually weathers away following control of the insect infestation.