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Blackmargined aphids (Pecan)

Article author: Bill Ree
Most recently reviewed by: Pat Porter (2018)

Common Name(s): Blackmargined Aphid

Pest Location

Vegetable and Fruit

Description

There are three species of foliage feeding aphids on pecan: the blackmargined aphid, Monellia caryella; yellow pecan aphid, Monelliopsis pecanis and black pecan aphid, Melanocallis caryaefoliae. Of these three, the blackmargined and yellow pecan aphid are also referred to a yellow aphids or honeydew aphids.

The winged adult blackmargined aphid can be identified by the wings being held in a horizontal position and by the black margins along the wing, Figure 1. The yellow pecan aphid, has clear wings which are held roof-like over the back of the body.

Habitat & Hosts

Blackmargined aphids can be found on pecan, Carya illinoensis (both improved cultivars and native trees) across the pecan belt. They are also found on water hickory, Carya aquatica.

Life Cycle

Blackmargined pecan aphids overwinter as eggs under the bark of trees. Nymphs emerge during the spring and feed primarily on the underside of the leaf on the primary and secondary leaf veins, Figure 2. During the summer, many generations of aphids are produced by unmated females giving birth to live female aphids. The time period from birth to adult is approximately 6 days and there can be 16 to 32 generations per year. All aphids during the growing season are females which give birth to live young. Males are not produced until the fall. Mature males mate with females and the females lay the overwintering eggs.

Both adults and nymphs feed on plant sap and excrete a sticky substance referred to as honeydew, Figure 3. A black sooty mold will grow in the honeydew which, if heavy enough, will reduce the photosynthetic ability of the foliage, Figure 4.

Management

If you live in the State of Texas, contact your local county agent or entomologist for management information. If you live outside of Texas, contact your local extension for management options.

Primary management of blackmargined aphids is with insecticides. Management options with insecticides include the use of several active ingredients that are selective for aphids as well as other insects that feed on plant sap.

Other suggestions for aphid management include only treating problem varieties (if practical), treating only when insect densities exceed the treatment threshold of an average of 25 aphids per compound leaf, and rotating insecticides with different modes of action.

Other management options can include planting winter legume cover crops to generate populations of beneficial predatory insects such as lady beetles and lacewings during the spring. Also, using insecticides selective for Lepidoptera pests when treating for early season insects such as the pecan nut casebearer can help conserve existing populations of beneficial insects.

Two of the main beneficial insect groups which prey on pecan aphids are lacewing larvae (Figure 5) and lady beetle adults and larvae (Figures 6 and 7). Pecan aphids are also parasitized by a small wasp, Aphelinus perpallidus. Parasitized aphids turn black (Figure 8) and should not be mistaken for the black pecan aphid.

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Southern green stink bug


Most recently reviewed by: Tyler Mays (2018)

Common Name(s): Southern Green Stink Bug

Pest Location

Row Crop

Description

Adults are about 1/2 to 3/4-inch in length and are solid green. Immature stages vary in color from black for very small nymphs to green for larger nymphs. However, the immature stages have a distinctive pattern of whitish spots on the abdominal segments. Nymphal stages are often found together in high numbers because eggs are laid in clusters that appear as rows of small barrels on and around suitable food sources. Development from egg to adult requires about 35 days, but varies with temperature. Up to five generations per year may occur with greater numbers appearing in the fall before adults overwinter.

Habitat & Hosts

The southern green stink bug feeds on a wide variety of developing fruit, including cotton, peaches and tomatoes, and seeds such as pecan, sorghum and soybeans. They also feed on the parts of many ornamental and wild plants.

In fruit, such as tomatoes, damage is of two types. When the young green fruit is injured, the cells at the site of feeding are killed by the toxic saliva injected by the bugs into the plant. This area of the fruit stops expanding, while the cells around the dead cells continue to expand by increasing their water content. The result is deformed fruit that appears to have dimples. This type of damage has been called “cat facing.” When ripened or nearly ripened fruit is injured, the injection of toxic saliva merely kills a cluster of cells that later forms an off-color hard mass in the fruit, reducing fruit quality and producing a bad flavor to the fruit. Some plant diseases are spread by stink bug feeding.

Life Cycle

Simple metamorphosis adults deposit barrel-shaped eggs; immature stages develop through five stages or instars that appear similar to adults except that they do not have fully developed wings. Several generations can be produced each year.

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