Pecan Phylloxera Identification and Control

Pecan Phylloxera Identification and Control

Phylloxera galls appear on leaves from insect feeding activities

Prevent repeated pecan phylloxera infestations from severely damaging or killing your pecan trees. Knowing how to identify and control phylloxera will help you stop this insect from slowly debilitating your tree and take measures to effectively control it.

toddsmariettatreeservices.com gathered the following information about pecan phylloxera, the damage it causes, how to identify it, and what can be done to control it.

What Is Pecan Phylloxera

Pecan phylloxera is an insect that can cause significant damage if ignored or treated incorrectly in pecan orchards. Phylloxera can attack pecan tree shoots, leaves, and fruit. Due to the life cycle of phylloxera, timing is very vital to controlling the infestation. Once you see that galls have developed, it is too late to stop the infestation in the current season. The following are three species of phylloxera and the galls they form:

Pecan Phylloxera (P. devastatrix Pergande) – This insect species produces large, green galls on stems, twigs, petioles, midribs, and nuts. Winged phylloxera emerge from these galls.

Pecan Leaf Phylloxera (P. notabilis Pergande) – This species causes small galls to develop next to the midribs or veins of leaflets. The galls are oval to spherical, open on the ventral surface of the leaf, are typically evenly green on the top, and often appear reddish beneath. Winged phylloxera also emerge from these galls.

Southern pecan leaf phylloxera (P. russellae Stoetzel) – This phylloxera species causes the formation of small galls on leaf surfaces between the veins. The galls are round and somewhat flat, open on the ventral surface. The opening will typically contain dense, short, white hairs. Phylloxera emerging from these galls are wingless.

Pecan Phylloxera Damages

Phylloxera damages can appear as dieback chlorosis fruit damage and allow secondary infestations

Pecan phylloxera in isolated cases does not cause any significant damage to its host tree. However, large and/or repeated infestations can result in the following:

  • General wilting and/or drooping
  • Chlorosis of affected foliage
  • Dieback of affected branches
  • Early leaf drop
  • Weakened/Declining tree health
  • Causes increased susceptibility to secondary infestations and diseases

Note: For trees with previous disease and infestation incidences (including repeated and heavy phylloxera infestations), significant phylloxera infestations can ultimately lead to or participate in the host tree’s death.

How To Identify Pecan Phylloxera

Pecan phylloxera are tiny insects resembling aphids (without the cornicles) that range from cream to a pale yellow color. Phylloxera have sucking mouthparts and are 1/10 to 1/5 inch long. Their feeding stimulates the tree to produce galls on leaves, stems, and nuts where wounded. The phylloxera reproduce inside the galls. All phylloxera species overwinter in the tree or orchard and feed on new growth in the spring.

Pecan Phylloxera Lifecycle

The three species of phylloxera follow somewhat identical lifecycles. Observe the following:

Eggs – Phylloxera overwinter as eggs in sheltered spots like bark on the tree trunk or branches, within opened/spent galls, underneath the carcasses of dead phylloxera, etc.

Stem Mothers – The young that hatch from overwintered eggs are referred to as “stem mothers” and appear around the same time new foliage and growth begin to emerge.

Gall Formation – As the stem mothers hatch, they migrate to emerging tissue to begin feeding. This feeding stimulates the host tree to develop galls that enclose the insect within a few days.

Phylloxera galls enclose and shield the insects as they mature

Nymphs – Inside the galls, stem mothers mature, lay their eggs, and die. Shortly after that, nymphs hatch from the eggs and feed until the galls split open in late spring or early summer, at which time new adults emerge.

The following are how each of the species continue their reproductive cycles:

Pecan Phylloxera (P. devastatrix Pergande) – Winged, asexual adults emerge from the galls and migrate to other parts of the same or nearby tree where they deposit small eggs that hatch into male insects and larger eggs that hatch into female insects. Once mated, the females die with a fertilized egg still inside them (protected for the winter). This species produces one generation of galls per year.

Pecan Leaf Phylloxera (P. notabilis Pergande) – Winged, sexual adults emerge from the galls resulting from the stem mother. These adults mate and the females locate a protected place to lay a single egg (which also hatch asexually) before they die. This species crawls to new areas of foliage on the same tree and forms a second and, sometimes, a third generation of galls in a single season.

Southern pecan leaf phylloxera (P. russellae Stoetzel) – These produce wingless, sexual adults in the galls resulting from the stem mother. The females will crawl to protected/secluded places to lay their single eggs. These eggs are typically not entirely laid by the female, remaining attached to her dead body. This species only produces one generation of galls per year.

Watch this video to see phylloxera insects inside a gall.

Pecan Phylloxera Control Measures

If any of the phylloxera species are present, insecticide applications should be made to your tree(s) between bud swelling and early leaf expansion (when the leaves have begun to unfurl). If galls are found, another insecticide application should be made the following year. Consider the following when acquiring an insecticide for phylloxera control:

  • Acquire adequate equipment to thoroughly distribute (spray) the insecticide on infested specimens
  • Select an insecticide containing a growth or reproductive inhibitor
  • Use insecticides containing carbaryl as an active ingredient; it is one of the most readily available phylloxera treatments for homeowner applications
  • Solutions containing neem oil are also highly effective, killing small soft-bodied insects like phylloxera on contact
  • Imidacloprid (made to mimic nicotine, which is lethal to insects) is also a good, systemic choice for phylloxera control.
  • Learn the recipe for how to make your own insecticidal soap to combat pests – toddsmariettatreeservices.com/insecticidal-soap-recipe-control-tree-pests/

You can reduce or eliminate the potential for such infestations by planting resistant cultivars and promoting their vigorous, healthy growth.

Tip: Insecticide applications must be made prior to gall formation. Once the insects are enclosed in the galls, reliable control is no longer possible.

Watch this video for more on pecan phylloxera

Disclaimer: This website provides general information only about a chemical or class of chemical products; it does not and cannot provide detailed safety information specific to any particular consumer product, it is not intended to be comprehensive or complete, and it should not be relied upon to ensure safe and appropriate use of any particular insect control product. Read product labels for warnings, advisories, and instructions.

Southern Pecan Leaf Phylloxera

In this article, you discovered information about the several pecan phylloxera species, the damage they can cause, ways to identify them, and control methods.

Knowing when to take action against phylloxera is as crucial as how to do it. Enacting well-informed and timed control measures will help you keep phylloxera infestations under control.

Ignoring or incorrectly treating a phylloxera infestation can allow its rapid proliferation, decline in overall tree health, and eventual tree death.

Sources:
hgic.clemson.edu/factsheet/southern-pecan-leaf-phylloxera/
entoweb.okstate.edu/ddd/insects/phylloxera.htm
extension.msstate.edu/sites/default/files/newsletter/bugwise-newsletter/2016/2016%20BugWise%20No%202%20-%20Pecan%20Phylloxera.pdf

Todd’s Marietta Tree Services

200 Cobb Pkwy N Ste 428 Marietta, GA 30062
(678) 505-0266

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