How to Manage Pests
UC Pest Management Guidelines
Whiteflies are tiny, flying insects that derive their name from the mealy white wax covering their wings and body. While adult whiteflies are similar in appearance, the immature stages are more distinctive. The pupa and other immature stages of the woolly whitefly are covered with curly, waxy filaments and are exclusively found on the undersides of leaves; pupae of the bayberry whitefly have a clear wax fringe around the body margin; pupae of the citrus whitefly have a distinctive Y-shape on their backs; and pupae of the ash whitefly have a thick band of wax down the back and a fringe of tiny tubes, each with a liquid droplet at the end.
Whiteflies suck phloem sap, which in some cases can cause leaves to wilt and drop when populations are large. However, the primary concern with whiteflies is the honeydew they produce. Honeydew excreted by nymphs collects dust and supports the growth of sooty mold; large infestations blacken entire trees, including fruit, as well as attract ants, which interfere with the biological control of whiteflies and other pests.
Chemical treatment of whiteflies is generally not necessary; exceptions are usually limited to where biocontrol has been severely disrupted. Enhance biocontrol by avoiding nonselective insecticides for other pests and by controlling sugar-feeding ants.
Several natural enemies attack the immature stages of whiteflies and provide partial to complete biological control when undisturbed by ants, dust, or insecticide treatment. Conserve natural enemies by controlling other pests with the least disruptive materials available and by controlling sugar-feeding ants.
Alternate row pruning to provide refuge for parasites may provide some benefits.
Inspect for whitefly throughout summer by looking for immature stages on the undersides of leaves directly above areas with honeydew, sooty mold, or both. Consider treatments if honeydew and sooty mold contamination of fruit reaches levels that are not tolerable. Treatments specifically targeting whitefly are usually not needed because usually at least one neonicotinoid (e.g., Assail, Admire, Nuprid, Provado) or insect growth regulator (e.g., Esteem, Applaud) that will suppress whiteflies has already been used one or more times on most citrus orchards to control scale and sharpshooter pests. No official treatment thresholds for whitefly exist.
|Common name||Amount to use||R.E.I.‡||P.H.I.‡|
|(example trade name)||(type of coverage)**||(hours)||(days)|
|The following materials are listed in order of usefulness in an IPM program, taking into account efficacy and impact on natural enemies and honey bees. When choosing a pesticide, also consider information relating to environmental impact. Not all registered pesticides are listed. Always read label of product being used.|
|(Assail) 70 WP||3.4–5.7 oz/acre (TC)||12||7|
|RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: most|
|PERSISTENCE: Pests: intermediate; Natural enemies: long|
|MODE OF ACTION GROUP NUMBER1: 4A|
|COMMENTS: Residues last for 4–6 weeks. Apply in 300-1000 gal water/acre; use higher volume if insects are inside the canopy on the wood. Toxic to bees exposed to direct treatment; apply only during late evening, night, or early morning. Toxic to vedalia beetle and should not be used in cottony cushion scale-infested orchards.|
|(Applaud)||2.14–2.86 lb/acre (TC)||12||3|
|RANGE OF ACTIVITY: Pests: narrow (scales, whiteflies); Natural enemies: predatory beetles|
|PERSISTENCE: Pests: intermediate; Natural enemies: intermediate|
|MODE OF ACTION GROUP NUMBER1: 16|
|COMMENTS: For use on all varieties. Toxic to vedalia beetles. Most effective if applied after peak emergence of the first generation of crawlers. Apply after the crawlers have settled down and formed white caps. Slow-acting; This product does not kill the scale until they molt, so decline of the population is usually not observed until the next generation.|
|(Admire Pro)||7–14 fl oz/acre||12||0|
|(Nuprid) 1.6F||10–20 fl oz/acre||12||0|
|RANGE OF ACTIVITY: Pests: narrow (aphids, glassy-winged sharpshooters); Natural enemies: predatory beetles and parasites|
|PERSISTENCE: Pests: long; Natural enemies: intermediate|
|MODE OF ACTION GROUP NUMBER1: 4A|
|COMMENTS: Apply to soil; remains effective 4–5 months. Moderately effective against nymphs and adults. Pre-wet soil before treatment is applied. Very toxic to bees; do not apply during bloom because bees may be drawn to irrigation water. For optimum uptake, apply to newly planted trees or trees irrigated by drip, microsprinkler, or low-pressure irrigation systems. Emitters must provide even, uniform distribution of water. Lightly pre-wet soil for several hours before application to break soil surface tension. Once the irrigation system reaches operating pressure, inject the treatment into the system over a calculated time interval (generally 2 hours) to allow uniform distribution throughout the system. The use of a dye marker in the treatment solution is recommended to determine when lines are clear of the treatment. Once the solution has cleared all irrigation lines and emitters, continue irrigation to move the insecticide into the active root zone but do not overirrigate or cause runoff. Wait 24 hours before subsequent irrigations. Apply in citrus orchards May–July. Toxic to vedalia beetle and should not be used in cottony cushion scale-infested orchards.|
|(Esteem) 0.86 EC||16 oz/acre (TC or LV)||12||1|
|RANGE OF ACTIVITY: Pests: narrow (armored scale insects); Natural enemies: predatory beetles|
|PERSISTENCE: Pests: long; Natural enemies: long|
|MODE OF ACTION GROUP NUMBER1: 7C|
|COMMENTS: For use on all varieties. Toxic to vedalia beetles. Do not apply until the second generation of scale crawler activity (1800 DD after the biofix of first male flight). This is to allow the vedalia beetle time between March-June to eliminate cottony cushion scale populations. This application timing may not prevent scale from infesting fruit. Apply after the crawlers have settled down and formed whitecaps. This product does not kill the scale until they molt, so decline of the populations is usually not observed until the next generation.|
|**||LV - Low-volume uses 20–100 gal water/acre.|
|TC - Thorough coverage uses 750–2,000 gal water or more/acre, depending on tree size.|
|‡||Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) 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.|
|1||Rotate chemicals 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; chemicals with a 1B Group number should be alternated with chemicals 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). For additional information, see their Web site at http://www.irac-online.org/.|
UC IPM Pest Management Guidelines:
UC ANR Publication 3441