Description of the Pest
The European fruit lecanium, also known as the brown apricot scale, occurs throughout California, but is rarely a problem. This scale has one generation a year. It overwinters as a nymph on twigs and small branches. In spring, it grows rapidly and secretes large amounts of honeydew. The adult cover is domed, shiny brown, and about 0.25 inch in diameter with several ridges along the back. In late spring females lay many eggs that fill the entire space beneath the covers; after the eggs are produced, they die.
Damage
The European fruit lecanium sucks juices from leaves and twigs. Low to moderate populations apparently are not damaging, but heavy populations reduce terminal growth and vigor. The chief injury is the production of large amounts of honeydew. Sooty mold growing on the honeydew can cause blackened areas on leaves and fruit.
Management
Biological control is frequently effective; if treatment is needed, oil applied during dormancy or delayed dormancy is the most effective way to reduce populations of this pest and the least disruptive of biological control.
Biological Control
Many natural enemies help to control populations of European fruit lecanium. Common predators include lady beetles (Chilocorus orbus, Hyperaspis spp., Rhyzobius lophanthae), lacewings, the predaceous sap beetle (Cybocephalus californicus) and predatory seed bugs (Phytocoris spp.). Parasites include Aphytis spp., Coccophagus spp., Encarsia spp., and Metaphycus spp. Frequently, scales found during the growing season are heavily parasitized.
Monitoring and Treatment Decisions
Populations of European fruit lecanium can be controlled with oil in the dormant season or in summer. Additional pesticides are necessary only when populations are severe. High scale populations often result from the use of chemicals that are disruptive to parasites and predators. If a high degree of parasitization is observed, treatments may be delayed until late spring after crawlers emerge. Crawler emergence can be monitored with the use of sticky tape wrapped around tree branches where populations are active. Examine sticky tape weekly for evidence of tiny yellow nymphs.
Treat during delayed-dormant period if scale population or sooty mold was observed the previous year.
| Common name | Amount to use** | REI‡ | PHI‡ | ||
|---|---|---|---|---|---|
| (Example trade name) | (conc.) | (dilute) | (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. | |||||
| DELAYED-DORMANCY | |||||
| A. | NARROW RANGE OIL# | Label rates | See label | 0 | |
| MODE OF ACTION: Contact including smothering and barrier effects. | |||||
| COMMENTS: Oil alone can control moderate populations of soft scales. If orchard has a history of this pest, or high populations are present, add an insecticide to the spray (see below). Not all oils are organically acceptable; be sure to check individual products. | |||||
| B. | NARROW RANGE OIL | Label rates | See label | 0 | |
| MODE OF ACTION: Contact including smothering and barrier effects. | |||||
| . . . PLUS (for severe infestations only) . . . | |||||
| DIAZINON* | |||||
| (Diazinon 50W) | 1 1/4 lb/100 gal water | 96 (4 days) | 21 | ||
| MODE-OF-ACTION GROUP NUMBER1: 1B | |||||
| COMMENTS: Organophosphate insecticides used during delayed dormancy are very toxic to honey bees. Remove bees from orchard if cover crops or weeds are in bloom. Oil sprays may injure trees that are water stressed. It is advisable to postpone an oil application to water-stressed trees until winter rains have replenished soil water and the tree bark is noticeably moist. Resistance to diazinon has been a problem in some populations of San Jose scale. Levels in surface waters of this material that are high enough to be toxic to certain aquatic invertebrates have occurred following rains in January and February; avoid runoff into surface waters. | |||||
| . . . or . . . | |||||
| PYRIPROXYFEN | |||||
| (Seize 35WP) | 4–5 oz/acre | 12 | 14 | ||
| MODE-OF-ACTION GROUP NUMBER1: 7C | |||||
| COMMENTS: An insect growth regulator that suppress egg hatch. Good coverage is essential for good control. Use allowed under a supplemental label. | |||||
| ** | For concentrate applications, use the amount given in 80–100 gal water/acre, or lower if the label allows; for dilute applications, amount is per 100 gal water to be applied in 300–400 gal water/acre, according to label. |
| ‡ | 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. |
| * | Permit required from county agricultural commissioner for purchase or use. |
| 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 are assigned by IRAC (Insecticide Resistance Action Committee). |
| # | Acceptable for use on organically grown produce. |