Description of the Pest
Brown soft scale is a mottled, yellow-brown when young, becoming darker at maturity. It has three to five generations per year and is often found on the nut. Adult scales are flattened and elongated, resembling a football sliced in half and about 1/8 inch (3.3 mm) in length.
Black scale is similar in size to the brown scale, dark brown to black, later becoming more mottled black and brown. It has an H-shaped ridge on the dorsum. There is generally only one generation per year in the Central Valley. However, in some years two generations have been detected.
Frosted scale is elongated, slightly humped, and has a waxy, white frostlike coating in spring. It is about 1/4 inch (6.4 mm) at maturity and has one generation per year. It is found in the warmer interior growing areas.
European fruit lecanium is identical to the frosted scale but does not have the frosted coating. High temperatures early in summer will increase mortality of immature stages of European fruit lecanium.
Immature stages of these scale species are very small (about 1/64 inch) and difficult to distinguish from each other; look for the adults nearby to determine which species is present. Soft scales molt twice before they reach maturity. The stage just before the adult is frequently referred to as the rubber stage. In this stage, the scales remain soft, somewhat translucent and are still susceptible to parasitism. Upon molting to adults, the shell hardens and becomes opaque.
Damage
In spring, soft scales produce heavy amounts of honeydew, providing a substrate on which sooty mold grows. Sooty mold growth covers leaves and can affect photosynthesis. Moderate-to-high scale populations can also retard shoot growth and shell splitting. Scales are most common on vigorously growing trees.
Management
These scales are normally kept under control by native parasites. Because of the increase in the use of permethrin treatments for true bugs in pistachio, natural enemies of scales are more frequently killed, and soft scales are becoming more prevalent.
Biological Control
There are a number of effective parasites of these soft scales. Most are tiny parasitic wasps in the genus Metaphycus. Metaphycus luteolus destroys the scale in its early instars before it can reproduce or cause substantial injury. This parasite produces several generations during each scale generation. In addition, predators, including the predaceous lady beetle, Rhyzobius (Lindorus) lophanthae, and green lacewings, Chrysopa and Chrysoperla species, feed on these scales.
There is a strong relationship between phytocoris bugs and soft scale. Where phytocoris bugs are plentiful, scale density is commonly low. During March and April, young adult soft scales (prior to forming their crustlike covering and laying eggs) and soft scale eggs are a primary food source for phytocoris bugs. In fall, phytocoris bugs feed on second-instar scales that are migrating from the leaves to the woody shoots.
Organically Acceptable Methods
Biological control and oil sprays in the dormant period are acceptable for use in an organically certified crop.
Monitoring and Treatment Decisions
In early to mid-January, examine one-year-old fruiting wood for live and parasitized scale paying special attention to previously infested areas. Look at 12-inch dormant shoots that are randomly selected from throughout the orchard.
- A light-to-moderate population in early February would be an average of one to five live scale per inch of fruiting wood.
- A heavy population would be an average of 10 or more live scale per inch.
Other factors to consider when making treatment decisions are the age, vigor, and split nut percentages.
Apply a dormant treatment in mid-February before the scales reach the rubber stage of development. For optimal control, treat frosted scale before its waxy coating develops, and treat European fruit lecanium before it reaches the rubber stage in late February.
Depending upon weather conditions and scale pressure, re-treatment may not be necessary for 3 to 5 years.
Pesticides and Natural Enemy Releases
Not all registered pesticides are listed. The following are ranked by their IPM value, with the most effective and least harmful to natural enemies, honey bees, and the environment listed at the top of the table. When choosing a pesticide, consider information related to water and air quality, resistance management, and the pesticide's properties and application timing. Use PestManage to compare summarized management options for different pests in the same crop. Always carefully read the label of the product being used and take all necessary precautions when handling pesticides.
| Rank | Active ingredient | Example trade name | Group | Group Order | MoA 1 | Amount per acre | REI (hours) ‡ | PHI (days) ‡ | Comments | Selectivity 2 | Bees 3 | Predatory mites 4 | Predators 5 | Parasitoids 5 | Residue duration 6 | Leaching(fish) 7 | Adsorbed runoff(fish) 8 | Solution runoff(human) 9 | Leaching(human) 10 | Solution runoff(human) 11 | Last updated 12 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
|
Centaur WDG | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
16 |
34.5–46 oz | 12 | 60 | A growth regulator. Most effective on cr... | narrow | low | high 13 | low | long | intermediate | low | high | low | intermediate | 10/2014 | ||
| Sevin XLR Plus | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
1A |
4–5 qt | 12 | 14 | Tank mix with narrow range oil at a rate... | broad | low | high | high | long | low | low | intermediate | low | low | 10/2014 | |||
|
|
Omni Supreme # | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
UNM |
4–6 gal | 12 | 0 | Narrow range oil. No more than 6% v/v so... | — | — | — | — | — | very low | low | very low | very low | very low | 10/2014 | ||
|
|
Seize 35 WP | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
7C |
4–5 oz | 12 | 21 | Insect growth regulator. | narrow | low | high 13 | low | short | low | low | high | very low | very low | 10/2014 |
Legend
- ‡ a b Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without personal protective equipment. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases, the REI exceeds the PHI. The longer of the two intervals is the minimum time that must elapse before harvest.
- * a Permit required from county agricultural commissioner for purchase or use.
- # ↩ Acceptable for use on certified organic crops. Check with your certifier to confirm before application.
- 1 ↩ Group numbers for insecticides and miticides are assigned by the Insecticide Resistance Action Committee (IRAC). Insecticides with unknown modes of action are assigned mode-of-action group numbers (MoAs) that begin with UN. Rotate pesticides 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.
- 2 ↩ Range of insect and mite groups affected by a pesticide. Broad means the pesticide affects most groups of insects and mites; narrow means the pesticide affects only a few specific groups.
- 3 ↩ Risk of harm to honey bees. For more information, see Bee Precaution Pesticide Ratings.
- 4 ↩ Risk of harm to predatory mites. Toxicities are generally to western predatory mite, Galendromus occidentalis. Where differences have been measured in toxicity of the pesticide-resistant strain versus the native strain, these are listed as pesticide-resistant strain or native strain.
- 5 a b Risk of harm to parasitoids and general predators. Toxicities are averages of reported effects and should be used only as a general guide. Actual toxicity of a specific insecticide depends on factors including the application rate, environmental conditions, and the life stage and species of a parasitoid or predator.
- 6 ↩ Length of time residue affects natural enemies. Short means hours to days; moderate means days to 2 weeks; and long means many weeks or months.
- 7 ↩ Risk of harm to fish from leaching, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 8 ↩ Risk of harm to fish from adsorbed runoff, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 9 ↩ Risk of harm to fish from solution runoff, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 10 ↩ Risk of harm to humans from leaching, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 11 ↩ Risk of harm to humans from solution runoff, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 12 ↩ Date information was last updated in the UC IPM Pest Management Guidelines.
- 13 a b Kills lady beetles.
UC IPM Pest Management Guidelines: Pistachio
UC ANR Publication 3461
R.H. Beede (emeritus), UC Cooperative Extension Kings County
W.J. Bentley (emeritus), UC IPM and Kearney Agricultural Research and Extension Center, Parlier
K.M. Daane, Kearney Agricultural Research and Extension Center, Parlier
D.R. Haviland, UC IPM and UC Cooperative Extension Kern County
Acknowledgement for Contributions to Invertebrates
R.E. Rice, Kearney Agricultural Research and Extension Center, Parlier
