How to Manage Pests

UC Pest Management Guidelines

Grape

European Fruit Lecanium Scale

Scientific name: Parthenolecanium corni

(Reviewed 6/06, updated 4/14)

In this Guideline:


Description of the Pest

European fruit lecanium is a scale insect that is also known as the brown apricot scale. The adult female's domed shell is shiny brown and about 0.4 inch in diameter. Adult females are mostly found on 1- to 3-year-old wood on the underside of woody canes, cordons, and spurs where they remain for the rest of their lives. Females reproduce parthenogenetically (without mating), and eggs are laid in spring (beginning in April) beneath the female's body. Crawlers hatch from May through most of June. They move to the shoots and leaves of the current season's growth and molt to second instars from June to July.

In the North Coast a portion of the second–instar population continues development and becomes adults that produce a second generation. The crawlers of the second generation may be found on leaf petioles and shoots in August. Beginning in September, second-instar nymphs from both the first and second generation migrate back to 1- to 3-year-old wood. They overwinter under the bark in the second-instar stage. Early in spring, the second instars molt to the third-instar stage and then quickly develops into mature females that begin laying eggs in April and May. There is usually only one generation each year, but a portion of the population in the North Coast will have two generations. The second generation has not been observed in other grape-growing regions.

Damage

European fruit lecanium scale produces honeydew as it feeds. Sooty mold may grow on the honeydew, causing blackened areas on leaves and fruit. When European fruit lecanium occurs in abundance, it may stunt vine growth.

Management

Parasites and predators often keep populations below damaging levels. Only when populations increase to great numbers should insecticide applications be considered.

Honeydew-seeking ants must be controlled to allow natural enemies of scale to aid in its control. This is best accomplished either with tillage or by treating the ants with an insecticide. See the section on ANTS for additional information on their control.

Biological Control

European fruit lecanium is attacked by several species of parasites, including Aphytis spp., Coccophagus spp., Encarsia spp., and Metaphycus luteolus. Important parasites in the North Coast region are Metaphycus insidiosus, Coccophagus lycimnia, and Blastothrix longipennis. Frequently, second-instar scales may be heavily parasitized early in spring before budbreak. In addition, many common predators help control this scale. These include lady beetles (Chilocorus orbus, Hyperaspis spp., Rhyzobius lophanthae), lacewings, the predaceous sap beetle (Cybocephalus californicus) and predatory seed bugs (Phytocoris spp.).

Organically Acceptable Methods

Organically acceptable methods of controlling European fruit lecanium include biological control and oil sprays.

Monitoring and Treatment Decisions

Monitor closely throughout the year and make a map of infested areas in the vineyard. Monitor 1- to 3-year-old wood in early March for the presence of parasitism on second-instar scale nymphs. Place the scales in gelatin capsules (available from pharmacies) to detect parasite emergence, or look for round exit holes on the scale bodies. You can also monitor female development on old wood. Monitor for crawler emergence in May by placing double-sided sticky tape around 1-year-old wood near the females, or by turning over the females and looking for crawlers.

The crawler stage is the stage most susceptible to chemical treatment, especially when using summer oil sprays. Crawlers emerge for a period of about 6 weeks, starting in mid-May. Treatment levels for scale have not been established. Determine the need for treatment of European fruit lecanium by evaluating records of honeydew from the previous season. Time treatment by monitoring for egg hatch in May; turn 10 females upside down and note if crawlers are present among the eggs. Look for mature females under cordons.

Apply the first treatment when 50% of the females show egg hatch (i.e., there are some crawlers below them). Repeat monitoring again in 2 weeks and time treatment to when 90% of the females show crawlers, or treat with imidacloprid in mid- to late May. High temperatures in the summer months may reduce populations somewhat. If populations are high in September and grapes have been harvested, apply a treatment of oil before mid-October. In late season varieties or cool regions where harvest is late, an oil treatment may not be effective if the second instars have already moved under the bark for the winter.

When monitoring late in the dormant season, watch for ants. If ants are present, look closely for mealybugs and lecanium scale as outlined in DELAYED-DORMANT AND BUDBREAK MONITORING (wine and raisin grapes or table grapes) and record your results on a monitoring form (PDF).

Common name Amount per acre** R.E.I.‡ P.H.I.‡
(example trade name)   (hours) (days)

  Calculate impact of pesticide on air quality
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. Not all registered pesticides are listed. Always read the label of the product being used.
 
SUMMER
 
A. NARROW RANGE OIL#
  (Omni Supreme and others) Label rates 4 0
  MODE OF ACTION: Contact including smothering and barrier effects.
  COMMENTS: Apply at 50% and again at 90% egg hatch. Be sure that vines are well watered and do not apply at least 10 days before and after a sulfur application to avoid phytotoxicity. Works by contact activity only so good coverage is essential. Check with certifier to determine which products are organically acceptable.
 
B. NEEM OIL#
  (Trilogy) 1–2% 4 0
  MODE OF ACTION: Unknown. A botanical insecticide.
  COMMENTS: Make two applications: one at 50% and one at 90% egg hatch.
 
C. IMIDACLOPRID
  (Admire Pro - Soil) 7–14 fl oz 12 30
  (Admire Pro - Foliar) 1.0–1.4 fl oz 12 0
  MODE-OF-ACTION GROUP NUMBER1: 4A
  COMMENTS: Treat in mid- to late May. Most effective in drip-irrigated vineyards with sandy soils that are not on deficit irrigation. Efficacy may be reduced in high clay soils. If two applications are required because of coarse soils or where the longest period of protection is required, make the second application 21 to 45 days after the bloom application. Apply a total of 7 to 14 fl oz/acre; the full rate of 14 oz/acre is recommended where vigorous vine growth is expected or in warmer growing areas such as the San Joaquin or Sacramento valleys. To protect honey bees, apply foliar sprays only during late evening, night, or early morning when bees are not present.
 
POSTHARVEST
 
A. NARROW RANGE OIL#      
  (Omni Supreme and others) Label rates 4 0
  MODE OF ACTION: Contact including smothering and barrier effects.
  COMMENTS: Be sure that vines are well watered and do not apply at least 10 days before and after a sulfur application to avoid phytotoxicity. Works by contact activity only so good coverage is essential. Check with certifier to determine which products are organically acceptable.
 
** Apply with enough water to provide complete coverage.
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 R.E.I. exceeds the P.H.I. The longer of two intervals is the minimum time that must elapse before harvest.
# Acceptable for use on organically grown produce.
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). For information, see their Web site at http://www.irac-online.org/.

IMPORTANT LINKS

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Grape
UC ANR Publication 3448

Insects and Mites

W. J. Bentley, UC IPM Program, Kearney Agricultural Research Center, Parlier
L. G. Varela, UC IPM Program, Sonoma County
F. G. Zalom, Entomology, UC Davis
R. J. Smith, UC Cooperative Extension, Sonoma County
A. H. Purcell, Environmental Science, Policy and Management, UC Berkeley
P. A. Phillips, UC IPM Program, Ventura County
D. R. Haviland, UC IPM Program, Kern County
K. M. Daane, Kearney Agricultural Research Center, Parlier
M. C. Battany, UC Cooperative Extension, San Luis Obispo County
Acknowledgment for contributions to Insects and Mites:
J. Granett, Entomology, UC Davis

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