Phylloxera caryaesemen

(Shimer, 1869)

pecan phylloxera, pecan nut phylloxera

Phylloxera caryaesemen is a small, soft-bodied, gall-forming insect closely related to aphids that attacks pecan trees (Carya illinoinensis). It is considered the most damaging phylloxera on pecans because it attacks shoots and developing nuts, unlike the related pecan leaf phylloxera which feeds only on leaves. Heavy can reduce current-year yield, impair tree vitality, and diminish subsequent production. The insect induces abnormal plant growths (galls) by secreting substances that stimulate tissue development, with nymphs completing development inside these protective structures.

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Pronunciation

How to pronounce Phylloxera caryaesemen: /fɪˈlɒksərə ˌkɛərɪeɪˈsiːmɛn/

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Distinguished from pecan leaf phylloxera (Phylloxera caryaecaulis) by gall location: P. caryaesemen forms galls on shoots and nuts, while P. caryaecaulis forms galls only on leaves. Galls on shoots and nuts indicate P. caryaesemen. The cannot be reliably distinguished by external appearance of the insect itself; identification requires examination of gall placement on the plant. Winged may be found when galls crack open in late spring to early summer.

Images

Appearance

Tiny, soft-bodied insect with . Nymphs are minute and pale. are winged and emerge from galls when mature. The itself is difficult to observe directly as nymphs are enclosed within galls during most of their development. Galls induced on pecan shoots and nuts range from 1/10 to 1 inch in diameter, appearing as conspicuous swellings on new growth.

Habitat

Pecan orchards and native pecan groves. Requires developing pecan shoots and nuts for gall formation. spread slowly between trees due to limited capability of .

Distribution

Native to North America where pecan (Carya illinoinensis) occurs naturally or is cultivated. Present in pecan-growing regions of the United States, particularly Texas and surrounding states. Distribution corresponds with commercial and native pecan production areas.

Seasonality

overwinter in bark crevices. Nymphs emerge during spring bud break and initiate gall formation on new growth. emerge from galls in late spring to early summer. Unlike pecan leaf phylloxera, this does not produce additional of galls in the same season.

Diet

Feeds on phloem sap of pecan (Carya illinoinensis), specifically from developing shoots and nuts. Nymphs feed continuously while enclosed within galls.

Host Associations

Carya illinoinensis - primary pecan; attacks shoots and nuts

Life Cycle

Overwinters as in bark crevices. Eggs hatch in spring at bud break; nymphs crawl to new growth and initiate feeding. Feeding stimulates gall formation; nymphs become enclosed within developing galls and complete development inside. Galls crack open in late spring to early summer, releasing winged . Adult females seek protected places on bark, deposit eggs within their bodies, and die; eggs remain inside maternal bodies through winter. No second of galls is produced in the same season.

Behavior

Nymphs are sedentary, remaining within galls throughout development. have limited capability; spread slowly from tree to tree. Females deposit within their own bodies rather than on plant surfaces.

Ecological Role

Herbivore that induces plant gall formation. Acts as a pest in agricultural systems, reducing pecan yield and tree vigor. May serve as early-season food source for hickory shuckworm larvae, which feed within phylloxera galls before pecan nuts are available.

Human Relevance

Significant agricultural pest of commercial pecan production. Economic damage includes direct nut loss, reduced tree vitality, and diminished subsequent-year production. Managed through varieties, targeted applications timed to hatch before gall formation, and conservation. Insecticides must be applied after bud break when new growth is 1-2 inches long but before nymphs are protected inside galls.

Similar Taxa

Phylloxera caryaecaulisAlso attacks pecan but forms galls only on leaves rather than shoots and nuts; considered less damaging; may produce multiple per season
Phylloxera caryaeRelated hickory-feeding with similar but different preference