Description of the Pest
Sweetpotato 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. Sweetpotato 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 sweetpotato 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 sweetpotato whitefly feeding.
Management
Fields planted downwind from other sweetpotato 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 sweetpotato 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 sweetpotato whitefly in artichoke.
Whitefly control with insecticides is maximized by thorough spray coverage. Ground application may give more complete coverage than air.
| Common name | Amount per acre** | REI‡ | PHI‡ | |
|---|---|---|---|---|
| (Example trade name) | (hours) | (days) | ||
| Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Always read the label of the product being used. | ||||
| A. | BIFENTHRIN | |||
| (Brigade WSB) | 16 oz | 12 | 5 | |
| (Brigade 2 EC) | 6.4 fl oz | 12 | 5 | |
| MODE-OF-ACTION GROUP NUMBER1: 3A | ||||
| COMMENTS: Do not exceed 0.5 lb a.i./acre per season. | ||||
| B. | AZADIRACHTIN | |||
| (Neemix 4.5)# | Label rates | 4 | 0 | |
| MODE-OF-ACTION GROUP NUMBER1: un | ||||
| COMMENTS: Check with organic certifier to determine which products are organically acceptable. | ||||
| C. | NEEM OIL | |||
| (Trilogy)# | 1–2% solution | 4 | 0 | |
| MODE-OF-ACTION GROUP NUMBER1: un | ||||
| COMMENTS: Thorough coverage is important; apply in a minimum of 75 gal water/acre. Check with organic certifier to determine which products are organically acceptable. | ||||
| ** | Mix with enough water to provide complete coverage. |
| ‡ | Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases, the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest. |
| # | Acceptable for use on organically grown produce. |
| 1 | Rotate insecticides with a different mode-of-action group number, and do not use products with the same mode-of-action group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a group number of 1B; insecticides with a 1B group number should be alternated with insecticides that have a group number other than 1B. Mode-of-action group numbers (un = unknown or uncertain mode of action) are assigned by IRAC (Insecticide Resistance Action Committee). |