Phylloxera rimosalis

Pergande, 1904

pecan leaf phylloxera

Phylloxera rimosalis is a tiny, soft-bodied insect closely related to aphids that forms galls exclusively on pecan leaves. It is one of two economically important phylloxera attacking pecans, the other being the more damaging pecan phylloxera (Phylloxera devastatrix) which attacks shoots and nuts. Extensive of P. rimosalis may cause some defoliation, but the species is generally less destructive than its . The insect has been observed in Texas and is managed as a pest of commercial pecan orchards.

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

North American Phylloxerinae affecting Hicoria (Carya) and other trees (1904) (14590179748) by Internet Archive Book Images. Used under a No restrictions license.

Pronunciation

How to pronounce Phylloxera rimosalis: /fɪˈlɑksərə rɪˈmoʊsəlɪs/

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

Identification

Distinguished from the pecan phylloxera (Phylloxera devastatrix) by its restriction to leaf tissue; pecan phylloxera attacks shoots and nuts and forms galls on these structures. Leaf galls of P. rimosalis may be confused with those of other gall-forming insects, but the combination of (pecan), location (leaves only), and gall (1/10 to 1 inch diameter swellings that crack open) is diagnostic. The is also distinguished from aphids by its gall-forming habit and more complex involving gall-enclosed .

Images

Habitat

Found in pecan orchards and areas with native pecan trees (Carya illinoinensis); requires new leaf growth for gall formation. move slowly from tree to tree because cannot fly long distances.

Distribution

Documented in Texas, where it is a known pest of commercial pecans; likely occurs throughout the native and cultivated range of pecan in the south-central United States.

Seasonality

hatch in spring during bud break; nymphs feed on new growth and induce galls. Winged emerge from galls in late spring (by late May). Second and sometimes third may occur if new growth remains available during the growing season. eggs are deposited in bark crevices by females in fall.

Diet

Nymphs and feed on pecan leaf tissue using to extract plant sap; feeding stimulates abnormal plant growth forming galls that enclose and protect the insects.

Host Associations

Carya illinoinensis - primary Pecan; the only known . Galls form exclusively on leaves.

Life Cycle

Overwinters as in bark crevices. In spring, nymphs emerge during bud break and feed on new leaf growth, inducing gall formation. Nymphs develop to adulthood inside galls. Galls crack open and winged emerge. Some adult females deposit eggs that hatch into nymphs, producing second and sometimes third if new growth is available. Other females overwinter, depositing eggs the following spring. Multiple generations per year possible under favorable conditions.

Behavior

Nymphs induce gall formation through feeding; the secreted substances stimulate abnormal plant tissue development that encloses the insects. are weak fliers and disperse short distances between trees. increase slowly due to limited ability.

Ecological Role

Herbivore that reduces leaf area and tree vigor through gall formation and potential defoliation; may indirectly affect nut production by depleting tree reserves. Serves as prey for natural enemies including lacewings, lady beetles, and predatory mites.

Human Relevance

Managed as a minor pest of commercial pecan production in Texas. treatment is recommended for infested trees in spring after bud break when new growth is 1 to 2 inches long, targeting nymphs before gall formation protects them. Native and improved pecan varieties vary in susceptibility. Less economically important than the pecan phylloxera (Phylloxera devastatrix) which attacks nuts and shoots.

Similar Taxa

Phylloxera devastatrixAlso attacks pecans but forms galls on shoots and nuts rather than leaves; considered more damaging to yield and tree vitality.
Phylloxera caryaecaulisAttacks hickory (Carya ) rather than pecan; forms galls on hickory leaves and petioles.

More Details

Management timing

must be applied after hatch in spring but before nymphs are protected inside galls. Optimal timing is after bud break when new growth is 1 to 2 inches long. Because spread slowly, only trees with visible galls typically require treatment.

Gall development

The galls range from 1/10 to 1 inch in diameter and completely enclose developing phylloxera. Galls eventually crack open (rimosalis = 'crack-bearing') to release winged .