Phylloxera perniciosa

Pergande, 1904

pecan phylloxera

Phylloxera perniciosa, commonly known as the pecan phylloxera, is a gall-forming insect that attacks shoots and nuts of pecan trees (Carya illinoinensis). It is considered the most damaging phylloxera affecting pecans, causing galls that reduce yield, impair tree vitality, and curtail subsequent production. The insect is closely related to aphids and survives winter as in bark crevices. Unlike the pecan leaf phylloxera, which only forms galls on leaves, this species attacks reproductive and vegetative shoots, making it economically significant in commercial pecan production.

Phylloxera perniciosa by the Smithsonian. Used under a CC0 license.

Pronunciation

How to pronounce Phylloxera perniciosa: /fɪˈlɒksərə pɜːˈnɪʃoʊsə/

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Identification

Distinguished from the pecan leaf phylloxera (Phylloxera notabilis or related ) by gall location: P. perniciosa forms galls on shoots and nuts, while leaf phylloxera forms galls only on leaf tissue. Galls on shoots and nuts are larger and more damaging than leaf galls. The species is also distinguished from other gall-forming insects on pecan by the timing of gall formation (spring, during bud break) and the specific location on new growth. Galls eventually crack open to release winged . The insect itself is rarely seen without dissecting galls.

Images

Appearance

Tiny, soft-bodied insect closely related to aphids. Nymphs are minute and pale. Winged emerge from galls and are small with membranous wings. The most visible sign of is the gall itself: abnormal, swollen plant growths ranging from 1/10 to 1 inch in diameter on shoots and young nuts.

Habitat

Found exclusively in pecan orchards and native pecan groves. Requires pecan trees (Carya illinoinensis) as . develop on new spring growth and spread slowly from tree to tree due to limited ability of .

Distribution

Native to North America; occurs throughout the pecan-growing regions of the United States, particularly Texas and the southeastern states where commercial pecan production is concentrated.

Seasonality

hatch in spring during bud break. Nymphs feed on new growth and induce gall formation when shoots are 1-2 inches long. Galls develop through spring and early summer, then crack open to release winged . No second galls are produced; females hide in bark crevices and die, with eggs protected inside their bodies over winter.

Diet

Feeds on pecan tree tissues (Carya illinoinensis). Nymphs insert needle-like mouthparts into new shoot and nut tissues, extracting plant sap. Feeding stimulates abnormal plant growth forming galls, within which the insect continues to feed and develop.

Host Associations

Carya illinoinensis - obligatePecan; sole known . Attacks shoots and nuts.

Life Cycle

Overwinters as protected within dead female bodies in bark crevices. Eggs hatch in spring during bud break. Nymphs crawl to new growth, feed, and induce gall formation. Once enclosed in galls, nymphs complete development to winged . Galls crack open in late spring to early summer; adults emerge, mate, and females deposit eggs in bark crevices. No additional gall are produced in a single season, distinguishing this from leaf-feeding phylloxera.

Behavior

Nymphs are sedentary once they begin feeding and inducing gall formation. have limited capability; spread slowly from tree to tree. Females seek protected bark crevices to deposit . The insect's feeding chemically manipulates plant tissue to create protective galls.

Ecological Role

Acts as a gall-forming herbivore that manipulates pecan plant development. Galls provide food and shelter for the insect at the expense of plant productivity. The reduces nut yield and tree vitality in commercial orchards. Natural enemies may include and , though specific relationships are not well documented.

Human Relevance

Major economic pest of commercial pecan production. Widespread reduce current-year yield, impair tree vitality, and reduce subsequent production. Managed through targeted applications timed to kill nymphs after hatch but before gall formation protects them. Native and improved pecan varieties vary in susceptibility. Because the insect cannot fly long distances, control can be achieved by treating only infested trees.

Similar Taxa

Phylloxera notabilis (pecan leaf phylloxera)Also attacks pecans but forms galls only on leaves; less economically damaging; produces multiple per season with second and third generation galls possible.
Phylloxera caryaecaulis (hickory phylloxeran)Attacks hickory (Carya) rather than pecan; forms galls on hickory leaves and petioles.

More Details

Control Timing

applications must be precisely timed: after bud break when new growth is 1-2 inches long, but before nymphs become enclosed within galls. Once galls form, the insect is protected from chemical control.

Varietal Susceptibility

Native pecan trees and improved varieties vary in susceptibility to phylloxera , though specific cultivars are not detailed in available sources.