How to Manage Pests

UC Pest Management Guidelines

DESCRIPTION OF THE PEST

Silverleaf whitefly adults are tiny (0.06 inch, 1.5 mm long), yellowish insects with white wings. Their wings are held somewhat vertically tilted, or rooflike, over the body and generally do not meet over the back but have a small space separating them.

Whiteflies are found mostly on the undersides of leaves. They fly readily when plants are disturbed. The tiny, oval eggs hatch into a first larval stage that has legs and antennae and is mobile. Both legs and antennae are lost after the first molt and subsequent stages remain fixed to the leaf surface. The last nymphal stage, often called the pupa or the red-eye nymph, is the stage that is easiest to identify. Silverleaf whitefly pupae are oval, whitish, and soft. The edge of the pupa tapers down to the leaf surface and has few to no long waxy filaments around the edge.

DAMAGE

Damage by silverleaf whitefly is mostly a problem in annual plantings of artichoke in warm climates. Feeding by whiteflies produces sticky honeydew on the leaves. Sooty mold may grow on the excreted honeydew. Artichoke seedlings and transplants may be stunted by silverleaf whitefly feeding.

MANAGEMENT

Fields planted down wind from other silverleaf whitefly hosts may experience problems with this pest. Monitoring field margins and applying spot treatments can effectively control this pest.

Cultural Control
Plant your earliest artichokes at least one-half mile upwind from cotton or melon fields. Destroy crop residues from these crops because they may harbor whiteflies after harvest. Remove weeds that host the whitefly and the virus. Present research indicates sprinklers may reduce whitefly populations and virus incidence.

Biological Control
Several wasps, including species in the Encarsia and Eretmocerus genera, parasitize whiteflies. Whitefly nymphs are also preyed upon by bigeyed bugs, lacewing larvae, and lady beetles. Indigenous parasites and predators and introduced parasites attack silverleaf whitefly, but do not keep it below damaging numbers.

Organically Acceptable Methods
Cultural and biological controls, azadirachtin, or neem oil are acceptable for use on organically certified crops.

Monitoring and Management Decisions
Routinely check field margins for whiteflies; these areas are usually infested first. Be especially alert for rapid population buildup when nearby host crops are in decline. During these critical periods, check artichoke fields twice weekly. Sticky traps may be useful in detecting initial whitefly migrations into fields. Allow beneficials an opportunity to control light whitefly infestations. If higher populations are present at the field margins than the field centers, then treat only the field margins. This approach will reduce treatment costs and help preserve beneficials in the field. Thresholds are not available for silverleaf whitefly in artichoke.

Whitefly control with insecticides is maximized by thorough spray coverage. Ground application may give more complete coverage than air.

PUBLICATION

UC IPM Pest Management Guidelines: Artichoke
UC ANR Publication 3434
Arthropods
M. A. Bari, Artichoke Research Foundation, Salinas
W. E. Chaney, UC Cooperative Extension, Monterey County
E. T. Natwick, UC Cooperative Extension, Imperial County
Acknowledgment for contributions to the arthropod section:
W. L. Schrader, UC Cooperative Extension, San Diego County
L. Handel and T. K. Shannon, Kleen Globe, Inc., Castroville, CA

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