How to Manage Pests

UC Pest Management Guidelines

Walnut

Codling Moth

Scientific Name: Cydia pomonella

(Reviewed 7/17, updated 7/17)

In this Guideline:


DESCRIPTION OF THE PEST

Codling moths overwinter as full-grown larvae in thick, silken cocoons under loose scales of bark or in trash on the ground near the trunk. Moth emergence usually coincides with the leafing out of early walnut cultivars. During the day, moths rest on branches and trunks. Codling moths can be distinguished from other small moths likely to occur in the orchard by the coppery markings on their wing tips.

The first flight of codling moth typically starts sometime from early March to early April and is from the overwintered generation. The flight of the overwintered generation may have two peaks (often referred to as 1A and 1B) and can last several months. These moths lay eggs that signal the beginning of the first generation. The second moth flight results when the larvae of the first generation complete their development. When the moths in the second flight lay their eggs, this starts the second generation. The following table outlines the life history of codling moth:

Generation Resulting moth flight Lay eggs for
overwintered first first generation
first second second generation
second third third generation
third fourth*  
* Only occurs in warm growing locations

Each overwintered female deposits about 30 eggs singly on leaves near nuts. Later generations of females will lay an average of 60 eggs on leaves or nuts. Eggs are disk-shaped and opaque white. Eggs of the overwintered generation hatch after 5 to 20 days, depending on the temperature, and young larvae bore into nutlets through the blossom end. Most nuts with codling moth damage from the overwintered generation drop to the ground along with blighted nuts. However, if damage occurs from second flight peak (1B) of overwintered codling moths and the weather is cool, all damaged nuts do not drop. So only use nut drop thresholds when there is no second peak in the flight of the overwintered generation.

Codling moth egg hatch period is dependent on temperatures but typically the egg hatch period for the overwintered generation lasts 4 to 6 weeks and 4 weeks for later generations. The egg hatch period is important for timing sprays. In cool springs or cool locations, the flight of the overwintering generation lasts longer than subsequent flights and has two peaks.

The larvae leave the nut after completing their development and pupate under loose bark on the tree. Adults of the first generation begin to emerge from the end of May to as late as the last week of June in the Central Valley, depending on the season. In coastal areas, emergence begins in late June to early July. Because of the higher temperatures, eggs and larvae of the first generation develop faster than those laid by the overwintered generation.

Newly-hatched second-generation larvae bore into walnuts anywhere on their surfaces but prefer the spot where two nuts touch. If the nut has hardened, it may take them up to a week to enter the nut. The larvae develop into adults that begin to emerge by late July or the beginning of August. In most valley locations they produce a third generation; in warmer locations a partial fourth generation may be produced in September. These later generations can cause significant damage. Older larvae leave the nuts and move to tree trunks or debris to spin cocoons and overwinter. Occasionally some may be present in nuts if they are harvested before the larvae have matured. However, most larvae found in nuts at harvest are navel orangeworm.

It is important to distinguish between codling moth and navel orangeworm damage. In harvest samples, it is easy to tell codling moth damage from navel orangeworm damage when the worms are present. Navel orangeworm has a brown crescent-shaped marking behind the head capsule on both sides of the first thoracic segment; this mark is absent in codling moth larvae. There can be multiple navel orangeworm larvae but only one codling moth larva per nut. If the worm is not present, look at the damage: navel orangeworm leaves behind more webbing and frass. However, navel orangeworm frequently infest nuts that were previously infested by codling moth, so if navel orangeworm is present, it doesn't mean codling moth wasn't previously there.

DAMAGE

The damage caused by the codling moth is different with each generation. First-generation larvae reduce yield directly by causing nutlets to drop from the tree. Codling moth-damaged nutlets have frass at the blossom end. Be careful not to confuse nuts damaged by codling moths with unpollinated nutlets or blight-infected nutlets, which have dark lesions but no frass and drop at the same time. Damage is generally most severe on early-season cultivars, although it has been increasing steadily over the years on late-season cultivars such as Chandler.

Nuts attacked by larvae from the last part of the first generation and from the second and third generations remain on the trees but are unmarketable because of the feeding damage to the kernel. These damaged nuts can also serve as a breeding site for the navel orangeworm. Feeding that is confined to the husk results in minor shell staining but no damage to the kernel.

You can often detect codling moth infestations by looking for frass produced by the larvae at the point of entry into the husk. Second-generation larvae often enter through the side of the husk where the two nuts touch. After the shell hardens, the larvae enter the nuts through the soft tissue at the stem end.

MANAGEMENT

Management options for codling moth in walnut orchards include both pheromone mating disruption and insecticide sprays. The options that work best for a given orchard depends on the size of the orchard and the trees and the degree of codling moth infestation. In all cases, monitor with pheromone (codlemone), pheromone plus kairomone (CM-DA combo), or both and check for damage. Monitoring and checking for damage is necessary to follow codling moth generations, assess the degree of infestation, and assess the effectiveness of control actions. Programs that use mating disruption alone or in combination with sprays of least-toxic insecticides or parasite releases pose fewer water quality and environmental risks than programs that rely on organophosphate or pyrethroid insecticides.

Biological Control

Natural enemies alone do not keep codling moth numbers below economic levels. In orchards where mating disruptants are used, augmentative releases of the tiny, naturally-occurring parasitic wasp Trichogramma platneri, which attacks codling moth eggs, can be helpful to control eggs laid by mated female moths immigrating into the area from surrounding areas, but this may not be economically feasible. They are most effective when the orchard's codling moth population is low.

Organically Acceptable Methods

Organically approved insecticides and some pheromone mating disruption products are acceptable for use in organically certified crops. While certain oil products are organically certified and will supply 30–40% egg kill, there is a concern of phytotoxicity with oils, especially when weather is hot. Oils have also been shown to kill the walnut aphid parasite, Trioxys pallidus. Always check with your organic certifier to determine what products are approved for organic certification.

Establishing Biofix and Accumulation of Degree-Days

In early March, place traps in your orchards to determine first moth emergence.

  • If using traps with standard 1 mg pheromone (1X) lures, put traps in the southeast quadrant of the tree about 6 to 7 feet high. Traps placed higher in the tree canopy catch more moths, which may be useful in orchards with low codling moth numbers.
  • Traps with CM-DA lures should be hung mid-canopy and are most useful in orchards that are either using mating disruption or near other orchards using mating disruption.

Biofix is the first date that moths are consistently found in traps and sunset temperatures have reached 62°F. All moths caught in traps with standard 1 mg pheromone lures will be males. Traps with CM-DA combo lures, which contain codlemone pheromone (the male attractant used in 1 mg lures) and a kairomone made of pear volatiles, attract only males before females emerge and both males and females thereafter. The first sustained catch of female moths in these traps is referred to as "female biofix", but degree-day calculations and the treatment timings are all based on the biofix established using male trap captures, regardless of the lure used for monitoring. To predict egg hatch, begin accumulating degree-days from the biofix, using a lower threshold of 50°F and an upper threshold of 88°F.

Because biofix points vary from orchard to orchard, monitor each orchard separately to determine the biofix point for that orchard. See Table 1 for information on setting biofix points for subsequent generations.

MONITORING AND TREATMENT DECISIONS IN A MATING DISRUPTION ORCHARD

Unless the orchard is isolated, mating disruption is most successful in large, uniform orchards on flat ground, with a square shape (as opposed to a narrow rectangular shape), and with relatively low to moderate numbers of codling moths. It is less effective in orchards with susceptible varieties (e.g., Ashley, Payne, Serr, Vina) or in orchards that have a history of high numbers of codling moths or economically significant codling moth damage. In these situations, make the transition to a mating disruption program using both mating disruption and chemical control the first year or two to reduce codling moth damage.

Air currents entering the windward (upwind) sides of orchards adjacent to open areas may reduce the effectiveness of mating disruption along orchard edges. In addition, the edges of orchards adjacent to other walnuts not under mating disruption may have immigration of mated females from those blocks. Monitor these situations closely, especially in puffer-treated orchards where the distance between dispensers is large. An insecticide spray applied 4 to 5 trees deep along the affected edge of the orchard may help reduce the risk of damage in these areas.

Setting Out Traps

Traps using standard 1 mg pheromone lures catch few or no moths when mating disruption is present. Therefore, in mating disruption orchards, use codling moth traps with CM-DA combo lures to monitor development and moth numbers.

  • Place CM-DA combo traps (1 trap per 25 acres) in the mid-canopy of trees. High counts of codling moths in these traps will help determine the need for supplementing mating disruption with insecticides.
  • Also, hang a smaller number of standard 1 mg traps (1 trap per 50 acres or per block) to assess the effectiveness and longevity of the mating disruptant. Hang these traps at 6 to 8 feet in the trees. If moths are caught in these traps consistently for 2 consecutive weeks, the mating disruptant may have broken down or expired, and insecticides may be necessary.

Change trap lures and bottoms at the frequency recommended by the manufacturer.

Setting Out Mating Disruptants

There are three types of pheromone mating disruption products available for use in walnuts:

  • Sprayable liquid formulations designed to be applied with standard orchard sprayers, which contain pheromones in tiny microcapsules that release pheromones into the air once they are deposited on leaves.
  • Hand-applied dispensersof various sorts that are hung in the orchard at rates ranging from 20 to 200 units per acre. Pheromones are released into the orchard continuously over a prolonged period of time.
  • Aerosol dispensers hung in the orchard at low densities, typically one unit per 1.5 to 2 acres. These mechanically dispense small amounts of pheromones into the orchard air at programmed intervals.

Aerosol or plastic dispensers: Hang in the upper quarter of the tree canopy before the historic date of first-flight biofix: typically mid-March in the central and southern San Joaquin Valley to early April further north.

Sprayable pheromone: Apply at or after biofix when leaves have started growing and are partially expanded. Sprayable formulations have short residual activity. They must be applied at 3- to 4-week intervals for sustained mating disruption, as applications at longer intervals have not been proven effective. Make additional applications shortly after the biofix of the second and third flights. When large moth numbers are present in an orchard, sprayable pheromones have been shown to reduce codling moth damage when added to a conventional spray program. As with hand-applied dispensers, standard 1 mg trap catches are helpful for deciding when sprayable pheromones need to be re-applied.

Nut Sampling

Check nuts for damage during each codling moth generation, particularly near the end of the generation when it is easier to see the frass (excrement). Examine 1,000 mid-canopy nuts in each block (20 nuts per tree on 50 trees per block) for signs of codling moth larval entry. Damaged nuts exceeding 1% after the first generation or 2% after the second indicate an infestation that may exceed 5% at harvest. In these cases supplement the mating disruption treatment with insecticide spray during the egg hatch of the next flight, which is 300 degree-days after the biofix.

At harvest, collect and crack out 1,000 nuts to assess damage and plan for next year.

Supplemental Treatments

When making the transition from managing codling moth with insecticides to mating disruption:

  • High codling moth numbers (i.e., where damage from previous season's harvest sample was over 4%): supplement mating disruption with insecticide applications to reduce the codling moth numbers.
  • Moderate numbers of moths (i.e., where the previous season's damage was 2 to 4% at harvest) or in the second year of transition: supplement mating disruption with sprays of insecticides that will not disrupt natural enemies.
  • Low moth numbers (where the harvest damage was less than 1% the previous season): mating disruption alone can be used.

Where insecticide sprays are needed, use degree-day calculations (see below) to apply insecticides at the most effective time.

MONITORING AND TREATMENT DECISIONS IN A CONVENTIONAL ORCHARD

In orchards sprayed with contact or ingested insecticides (e.g., spinosad and oil, organophosphates, pyrethroids, and carbamates), time all insecticide applications to kill larvae as they emerge from eggs. If insect growth regulators are used, apply insecticides before egg laying (Dimilin) or egg hatch (Confirm, Intrepid), depending on label instructions. If using a diamide insecticide (e.g., Altacor or Exirel), apply at or before peak egg laying of the targeted generation. Use pheromone (1 mg) or CM-DA combo traps, degree-days (DD), and sunset temperatures to monitor codling moth activity and determine when egg hatch occurs. If nearby orchards are using mating disruptants, use the CM-DA combo lure traps for monitoring.

Treatment Decisions

The need for treatment and the timing of sprays is different for the different generations of codling moth. The degree-day model used in this guideline for codling moth reflects the concept that each subsequent codling moth generation time is longer than the preceding one.

First Generation

The first flight of codling moth can last a long time and have two peaks (1A and 1B). To minimize interference with the walnut aphid parasite and, in most cases, avoid the necessity for aphid insecticide applications, it is best to delay sprays until the second generation or the end of the first generation (1B), especially in later-season varieties.

Low populations

If damage did not exceed 3% the previous season and less than an average of two moths per trap per night are being caught with 1 mg traps, delay insecticide applications until the second flight peak (1B). If you see an increase in trap catches, spray when 600 to 700 degree-days have accumulated from biofix.

Moderate to high populations

If damage exceeded 3% the previous season or more than an average of two moths per trap per night are being caught with 1 mg traps, plan to spray both the 1A and 1B larvae:

Treating 1A larvae

Apply a pesticide when 300 degree-days accumulate after biofix, using a short-residual material to minimize disruption of the aphid parasite, Trioxys pallidus.

Treating 1B larvae

When you see an increase in moths caught in traps around 600 to 700 degree-days from the first biofix, apply a second spray when the residual period (i.e., the length of time the insecticide controls the pest) of the first pesticide ends. Residual periods for many of the pesticides are listed in the treatment table below. In most cases, a range of days is given. The actual length of a residual period is influenced by several factors, including the pH of the solution and the susceptibility of the population to that material. If the population has developed any resistance to the material, then the residual period will be shorter than it would be for a highly susceptible population.

Second and Later Generations

Codling moth has two to four generations a year. Continue monitoring with traps and accumulating degree-days (as outlined in TABLE 1) until the crop is harvested or numbers decline to below damaging levels in September. At the beginning of each generation, determine the biofix point for that generation in order to predict the best treatment timing during egg hatch for that generation.

To time an insecticide application for second-generation larvae, determine the biofix for the second generation. This generally occurs around 1060 degree-days from the first biofix point. However, any increase in trap catches after 800 degree-days can be considered the biofix. To better determine this biofix, clean and service the traps around 700 degree-days and start checking traps more frequently.

If there was no second peak in the first flight of codling moth, the number of dropped nuts can be used to determine if the second generation requires an insecticide application. All nuts damaged by codling moth early in the season drop, except when there is a second peak of the first flight or if the weather is not hot enough.

  1. Look for frass at the blossom end of nuts to confirm that codling moth caused the drop.
  2. Examine all the nuts under the same 10 trees in an orchard block each week during the nut drop period (4 to 6 weeks from the end of bloom).
  3. Record the total number of damaged nuts per tree (not the percent damaged).
    • If an average of 4 or less infested nuts are found per tree, you can expect less than 5% codling moth damage by harvest without a spray.
    • If there are between 4 and 24 infested nuts per tree, spray at 250 degree-days from the second biofix and use a short residual pesticide.
    • If you collect more than 24 codling moth-damaged nuts per tree, apply an insecticide as soon as eggs of the second generation start hatching (250 degree-days from the second biofix), and use a long residual pesticide to cover the entire hatch period (about 1 month).
Third-generation Egg Hatch

A third (or fourth) generation of codling moth eggs does not occur every year in every location. Codling moth larvae normally go into diapause (winter dormant state) around August 22, but in warm years and warm locations they will have already started pupation before August 22, and these pupae will soon emerge as adults to produce a third generation. If 650 degree-days have accumulated between the peak of the second-generation flight and August 22, most of the codling moth will not go into diapause but will pupate and emerge in August to early September, depending on climate.

If degree-day accumulation data indicates a third generation will occur, use pheromone traps to establish a third biofix point around 1100 to 1200 degree-days from the second biofix. Apply a spray when 200 to 250 degree-days have accumulated from the third biofix unless trap catches are high, in which case spray at 160 degree-days. If needed, apply the second spray when the residual of the previous spray ends.

Table 1. Codling Moth Management in Walnuts.
EVENT ACTION
FLIGHT OF OVERWINTERED GENERATION
  • Hang traps out at bud break (first week in March) and determine first-flight biofix
Low populations
  • If damage did not exceed 3% the previous season and less than an average of 2 moths per trap per night are being caught with 1 mg traps, delay treatment until the second flight peak (1B); When you see an increase in trap catches, treat when 600 to 700 degree-days (DD) have accumulated from biofix.
Moderate to high populations
  • If damage exceeded 3% the previous season or more than an average of 2 moths per trap per night are being caught with 1 mg traps, treat both the 1A and 1B larvae.
First treatment (1A)1
  • Spray at 300 DD2 (or 250 DD if using an insect growth regulator) from first-flight biofix or when small nutlets first appear, whichever is later.
Second treatment (1B)1
  • Look for second peak about 600 to 700 DD from first biofix by checking traps frequently.
  • If a second peak occurs, spray when residual effectiveness of first treatment ends.
SECOND FLIGHT
  • Determine second biofix to time sprays for second-generation egg hatch.
  • Use trap catch data to detect resumption of moth flight activity and establish biofix. The second biofix will be when an increase occurs in trap catches between 800 to 1300 DD from first biofix (average is 1060 DD).
  • Begin accumulating degree-days from second biofix
  • Check traps frequently; trap maintenance important.
Visual monitoring
  • If there is a second peak in the first flight, use visual inspection. Look at a minimum of 10 nuts on each of 10 trees at least 10 feet up in the canopy.
  • If less than 2% infestation in visual inspection, don't treat.
  • If more than 3% infestation in visual inspection, spray at 250 DD2 from second biofix and use a short residual insecticide.
  • If there is more than 5% infestation in visual inspection, spray at 250 DD2 from second biofix and use a long residual pesticide to cover entire hatch period (about 1 month).
Monitoring nut drop
  • If there is no second peak in the first flight (overwintered generation), monitor nut drop to determine the need to spray.
  • If there are 4 or less infested nuts that have dropped from the tree, don't treat.
  • If there are 4 to 24 infested nuts per tree, spray at 250 DD from second biofix and use short residual insecticide.
  • If there are more than 24 infested nuts per tree, spray at 250 DD from second biofix and use long residual pesticide to cover entire hatch period (about 1 month).
THIRD FLIGHT
  • Time sprays for third generation egg hatch. Use trap catch data to detect resumption of moth flight activity. Third biofix is when trap increase occurs between 800 to 1300 DD from second biofix (average is 1100 DD).
  • Check traps frequently; trap maintenance important.
Low populations
  • Do not treat if there is no or little (less than 2%) evidence of canopy infestation.
Moderate to high populations
  • Spray at 300 DD2 (or 250 DD if using an insect growth regulator) from 3rd biofix when there is obvious canopy infestation (more than 2%).
FOURTH FLIGHT
  • Time sprays for fourth generation egg hatch. Use trap catch data to detect resumption of moth flight activity. Fourth biofix is when trap increase occurs between 800–1300 DD from third biofix (average is 1200 DD).
  • Check traps frequently, trap maintenance important.
Low populations
  • Do not treat if there is no or little (less than 2%) evidence of canopy infestation.
Moderate to high populations
  • Spray at 300 DD2 from fourth biofix when there is obvious canopy infestation (more than 2%).
HARVEST SAMPLE
  • Collect and crack out 1,000 nuts to assess damage and to plan for next year.

1 1A and 1B refer to the two flight peaks of the first codling moth flight

2Timing is 50 to 100 DD earlier for growth regulators

Additional Treatment Considerations

If there was a second peak in the first flight, not all of the infested nuts will have dropped, so visually inspect the tree canopy for infested nuts.

  1. Look at a minimum of 10 nuts on each of 10 trees at least 10 feet up in the canopy.
    • If less than 2% are infested, don't spray.
    • If greater than 2% infested nuts are found, a pesticide application is necessary.
  2. Apply an insecticide as soon as eggs of the second generation start hatching (250 degree-days from the second biofix).
    • Use a short residual material if the percent infestation is between 3 and 5, or
    • if greater than 5% infestation is found a long residual material to cover the entire hatch period (about 1 month).

For the third and fourth generation, the decision to spray must be based on a combination of factors including previous pesticide applications, number of nuts infested in the previous generation, trap catches, and the ability to harvest early. To determine the number of nuts infested in the previous generation, visually inspect 20 nuts at least 10 feet up in the canopy on 50 trees.

  • If less than 2% are infested, don't spray.
  • If greater than 2% are infested, spray.

If you spray, it is important to determine a biofix for third and fourth generations. The generation times get longer with each generation. Look for the third biofix around 1100 degree-days from the second biofix and for the fourth biofix around 1200 degree-days from the third biofix (the range for both biofix points is 800 to 1300 degree-days). Pesticide applications are often not needed at this time; but if stings are found on nuts, apply sprays 300 degree-days after the biofix.

Common name Amount to use** REI‡ PHI‡
(Example trade name) (conc.) (dilute) (hours) (days)
Calculate impact of pesticide on air quality
Bee precaution pesticide ratings
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.
 
Note: Residual periods mentioned in the comments will be influenced by many variables, including spray coverage, weather, resistance, population pressure, etc. and may vary from the actual effective control period, depending upon these variables.
 
MATING DISRUPTION
A. MATING DISRUPTANTS
  COMMENTS: Most effective in isolated blocks or larger blocks that have a squarish shape and low to moderate codling moth numbers, with trees of uniform size and moderate height. Consult with a crop advisor for help deciding whether specific orchards are suitable for mating disruption and information on how to deploy dispensers for maximum effectiveness. Apply just prior to first-flight biofix in mid-March to mid-April. Reapply if needed at the interval recommended on the label. Hang 1 mg pheromone traps at 6 to 8 feet high in the canopy and assess them weekly to ensure mating disruption product has not expired. Use traps baited with CM-DA combo lures high in the canopy to monitor population development. Check nuts for damage after each generation and treat with insecticides if needed to ensure a low level of damage at harvest. Be sure to monitor for other pests such as walnut husk fly, aphids, and redhumped caterpillar normally controlled by codling moth sprays.
 
  AEROSOL DISPENSERS#   Period of effectiveness (days)
  (Isomate-CM Mist, Isomate CM-Mist Walnut) 1 dispenser/1.5–2 acres 0 Up to 200
  (CheckMate Puffer CM-O,
CheckMate CM-O-Pro)
1 dispenser/1.5–2 acres 0 Up to 200
  COMMENTS: Hang aerosol dispensers in the upper third of tree canopies. Hang aerosol dispensers at a spacing of one per 180 to 200 linear feet in trees around the perimeter; within the orchard's interior, place units in a roughly square grid pattern to achieve an interior density of one per 2 acres. This will result in an overall density of one dispenser per 1.5 to 2 acres. Although densities of less than 1 unit per acre are not recommended by either manufacturer, research has demonstrated that densities of 1 unit per 1.5 to 2 acres provides good suppression where a substantial monitoring program (as described above) is carried out and supplemental sprays are applied in the first few years, if needed, to lower codling moth numbers. The pheromone plume released by aerosol dispensers is large and has been shown to reduce 1 mg trap catches up to 2000 feet downwind. Use CM-DA combo traps (as well as standard 1 mg traps) to monitor conventionally managed orchards near orchards with aerosol dispensers to provide an accurate assessment of codling moth numbers and activity.
 
  HAND-APPLIED DISPENSERS#   Period of effectiveness (days)
  (Isomate-CTT) 100–200 dispensers/acre 0 160+
  (Isomate-CM Ring) 20–40 dispensers/acre 0 160+
  (CheckMate CM-XL1000) 120–200 dispensers/acre 0 Up to 150 days
  COMMENTS: Attach dispensers to branches in the upper third of tree canopies. Apply dispensers individually in trees at a rate sufficient to give the recommended number of dispensers per acre. Hang lower density products such as the CM-Ring in a uniform pattern (e.g. every other tree in every row) to ensure even distribution of pheromone throughout the orchard. Make application shortly before first biofix.
 
  SPRAYABLE FORMULATIONS
  (CheckMate CM-F) 2.4–4.8 oz 4 NA
  COMMENTS: Sprayable formulations have short residual activity and should be applied at 3- to 4-week intervals for continuous suppression. Delay the first application until leaves have emerged and are partially expanded.
 
INSECTICIDE CONTROLS
 
Moderate to High Codling Moth Numbers
 
A. SPINETORAM
  (Delegate WG) 4.5–7 oz 4 1
  MODE-OF-ACTION GROUP NUMBER1: 5
  COMMENTS: Larvicide. The best time to apply is at egg hatch (about 200 DD). Do not make more than four applications per year. To reduce the development of resistance, do not make more than three consecutive applications of any group 5 insecticides (spinosad or spinetoram) per season and do not apply to more than one generation per season.
 
B. CHLORANTRANILIPROLE
  (Altacor) 3–4.5 oz 4 10
  MODE-OF-ACTION GROUP NUMBER1: 28
  COMMENTS: Larvicide. The best timing is to apply before egg hatch (about 200 DD). Do not make more than four applications per year. To reduce the development of resistance do not make more than three consecutive applications of any group 28 insecticides (anthranilic diamide) per generation per season.
 
C. CYANTRANILIPROLE
  (Exirel) 10–20.5 fl oz 12 5
  MODE-OF-ACTION GROUP NUMBER1: 28
  COMMENTS: To reduce the development of resistance do not make more than three consecutive applications of any group 28 insecticides (anthranilic diamide) per generation per season.
 
D. LAMBDA-CYHALOTHRIN*
  (Warrior II with Zeon) 2.56 fl oz 24 14
  MODE-OF-ACTION GROUP NUMBER1: 3A
  COMMENTS: Larvicide. Residual at the acre rate is about 21 days. Addition of oil improves coverage and aids in suppressing mites. During the first codling moth generation, add oil at 1% if the 1A eggs are being treated and at 0.5% for the 1B eggs. During the second generation add oil at 0.25%.
 
E. CYFLUTHRIN*
  (Baythroid XL) 2–2.4 fl oz 0.5–0.6 fl oz 12 14
  MODE-OF-ACTION GROUP NUMBER1: 3A
 
F. BIFENTHRIN*
  (Brigade WSB) 8–32 oz 2–8 oz 12 7
  MODE-OF-ACTION GROUP NUMBER1: 3A
  COMMENTS: Provides about a 21- to 28-day residual at the high label rate.
 
Moderate Codling Moth Numbers
 
A. ACETAMIPRID
  (Assail 70WP) 2.3–4.1 oz 0.271–1 oz 12 14
  MODE-OF-ACTION GROUP NUMBER1: 4A
  COMMENTS: Toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.
 
B. EMAMECTIN BENZOATE*
  (Proclaim) 3.2–4.8 oz 0.8–1.2 oz See comments 14
  MODE-OF-ACTION GROUP NUMBER1: 6
  COMMENTS: REI is 48 hours for poling, pruning, and thinning; 12 hours for all other activities.
 
C. PHOSMET
  (Imidan 70W) 5 lb 1–2 lb 7 days 28
  MODE-OF-ACTION GROUP NUMBER1: 1B
  COMMENTS: Do not apply after husk split. Provides a residual of about 21 days. Buffer to a pH of 5.5–6.0.
 
D. CHLORPYRIFOS*
  (Lorsban Advanced) 4 pt 1 pt 24 14
  MODE-OF-ACTION GROUP NUMBER1: 1B
  COMMENTS: A moderate residual insecticide (10–14 days) best used when codling moth numbers are moderate. Effective against Guthion- and pyrethroid-resistant populations. When codling moth trap catches are in the mid- to high range, two applications of this material will be needed to cover the entire codling moth egg-hatch period, which is usually about 1 month long in later generations. Because label restrictions allow no more than two applications per season, most effective control results if both applications are directed at the same egg hatch period, either in the first or second generation. Provides control of the hyperparasite that attacks the aphid parasite Trioxys pallidus. Highly toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging. Levels in surface waters of this material that are high enough to be toxic to certain aquatic invertebrates have occurred following rains; avoid drift and runoff into surface waters. Do not allow livestock to graze in sprayed areas. Certain formulations emit high amounts of volatile organic compounds (VOCs); use low-VOC formulations. Regulations affect use for the San Joaquin Valley from May 1 to October 31, 2017. Review the Department of Pesticide Regulation's updated fact sheet.
 
E. METHOXYFENOZIDE/ SPINETORAM
  (Intrepid Edge) 10–18 fl oz 4 7
  MODE-OF-ACTION GROUP NUMBER1: 18
  COMMENTS: Apply at the beginning of egg hatch, which is earlier than organophosphorous or carbamate insecticide timings. It is recommended that methoxyfenozide be applied at 200 degree-days after the first biofix.
 
F. METHOXYFENOZIDE
  (Intrepid 2F) 16–24 fl oz 4 7
  MODE-OF-ACTION GROUP NUMBER1: 18
  COMMENTS: An insect growth regulator that provides 10 to 18 days of residual protection depending on the rate of application and nut expansion. Kills young larvae but does not kill adult moths. It is a reduced risk insecticide that has little or no effect on beneficial insects and mites. Only use in orchards with low to moderate codling moth populations. Spray coverage is extremely important. Do not apply to large trees unless adequate spray coverage can be verified. Use no less than 100 gal water/acre for ground applications. Sprayer speed should not exceed 1.5 mph. The use of Latron B-1956, CS-7, or similar sticker-spreader is highly recommended. Apply at the beginning of egg hatch, which is earlier than organophosphorous or carbamate insecticide timings. It is recommended that methoxyfenozide be applied at 200 degree-days after the first biofix.
 
G. ESFENVALERATE*
  (Asana XL) 9.6–19.2 fl oz 4 fl oz 12 21
  MODE-OF-ACTION GROUP NUMBER1: 3A
  COMMENTS: Residual of about 14 to 21 days (lower rates have less residual activity). This is a broad-spectrum pesticide that is harmful to beneficials at higher rates and can cause outbreaks of aphids and mites. Lower rates may also be harmful to beneficials, but the effects of secondary pest outbreaks are less obvious. It is best to use broad-spectrum pesticides late in the season. Provides control of the hyperparasite that attacks the aphid parasite Trioxys pallidus, and it does not kill Trioxys. This pesticide is not effective on scales, so if you have a scale problem choose another chemical.
 
H. PERMETHRIN
  (Ambush)* 12.8–25.6 oz. 0.05–0.1 lb a.i. 12 1
  (Pounce 25WP)* 12.8–16 oz. 0.05–0.0625 lb a.i. 12 1
  MODE-OF-ACTION GROUP NUMBER1: 3A
  COMMENTS: Residual of about 14 to 21 days (lower rates have less residual activity). There is no university data on the effectiveness of this material on codling moth in walnuts; follow information for esfenvalerate. This is a broad-spectrum insecticide and the high rate will be harmful to beneficials. This material is not effective on scales, so if you have a scale problem choose another chemical. It also may cause mite outbreaks. Do not graze livestock in sprayed area.
 
I. CARBARYL*
  (Sevin) Label rates 12 14
  MODE-OF-ACTION GROUP NUMBER1: 1A
  COMMENTS: There has been little research on this pesticide in walnuts, but in apples carbaryl is a good codling moth material and has a residual period of about 28 days. Carbaryl causes mites to reproduce more rapidly, possibly resulting in mite outbreaks, so monitor for mites if carbaryl is used. This pesticide is best used later in the season. Highly toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.
 
Low Codling Moth Numbers
 
A. DIFLUBENZURON*
  (Dimilin 2L) 16 fl oz 12 28
  MODE-OF-ACTION GROUP NUMBER1: 15
  COMMENTS: An insect growth regulator that has a residual of about 21 days. It kills eggs, does not kill adult moths, and is safer to some beneficials than organophosphates and carbamates. Only use in orchards with low to moderate codling moth numbers. Coverage is extremely important: it is not recommended for the first generation because the rapid growth of leaves in spring does not allow for leaves to remain completely covered during the residual period (21 days.) Apply in a minimum of 125 gal water/acre and the ideal amount is 250 gal water/acre for mature trees. Ground speed should not exceed 1.5 mph. Diflubenzuron must be applied earlier than the other pesticides because it needs to be on the leaf before eggs are laid. Treatment timing is before the start of the second generation fight, which is about 800–900 degree-days from the first biofix and before the start of the third generation flight, which is 1800 to 1900 degree-days from the first biofix. Diflubenzuron is not a stand-alone material and should be used in combination with another control.
 
Supplemental Control in Organic Orchards
 
A. CYDIA POMONELLA GRANULOVIRUS#
  (Cyd-X, etc.) 1–6 fl oz 4 0
  COMMENTS: A larvicide; time to egg hatch at 200 to 250 degree-days; larvae must ingest to become infected by this virus. Make a second application 7 to 10 days later, a third application at 600 degree-days, and a fourth 7 days later for a total of 4 applications per flight.
 
B. SPINOSAD
  (Entrust)# 1.25–3 oz 0.3–0.75 oz 4 1
  MODE-OF-ACTION GROUP NUMBER1: 5
  COMMENTS: A short-residual insecticide. When combined with 1% spray oil to improve spray coverage, this insecticide is best used as a supplement to mating disruption. May be used without oil but may not be as effective. Only higher rates of spinosad have been tested for codling moth control. Spray coverage is extremely important. At best, controls 50 to 60% of population. Do not use more than 9 oz. of Entrust/acre per crop. Do not apply spinosad sprays less than 7 days apart. Limited experience with use in California walnuts.
  . . . PLUS . . .
  NARROW RANGE OILS# See label See label 4 0
  MODE OF ACTION: Contact including smothering and barrier effects.
  COMMENTS: Do not apply if trees have suffered from a lack of adequate soil moisture or other stressing factors (insect, disease damage, etc.) at any time during the year or if temperatures are expected to exceed 90°F at time of application. Do not apply after husk split. Not all oils are organically acceptable: check label and your organic certifying agency.
 
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 concentrate application, use the amount given in 80 to 100 gal water/acre, or lower if the label allows; for dilute application, amount is per 100 gal water to be applied in 300 to 500 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 these two intervals is the minimum time that must elapse before harvest may occur.
* Permit required from county agricultural commissioner for purchase or use.
# Acceptable for use on organically grown crops.
NA Not applicable.

IMPORTANT LINKS

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Walnut
UC ANR Publication 3471

Insects and Mites

J. A. Grant, UC Cooperative Extension, San Joaquin County
J. K. Hasey, UC Cooperative Extension, Sutter, Yuba, and Colusa counties
W. W. Coates, UC Cooperative Extension, San Benito County
R. A. Van Steenwyk, Insect Biology, UC Berkeley
E. J. Symmes, UC IPM Program, Butte County
S. J. Seybold, Entomology, UC Davis (walnut twig beetle)
R. M. Bostock, Plant Pathology, UC Davis (walnut twig beetle)

Acknowledgment for contributions to Insects and Mites:
W. J. Bentley, UC IPM Program, Kearney Agricultural Research and Extension Center, Parlier (Emeritus)
L. C. Hendricks, UC Cooperative Extension, Merced County (Emeritus)
W. H. Olson, UC Cooperative Extension, Butte County (Emeritus)
C. Pickel, UC IPM Program, Sutter and Yuba counties (Emeritus)
G. S. Sibbett, UC Cooperative Extension, Tulare County (Emeritus)
D. Light, USDA, Albany, CA (Emeritus)(Codling Moth)

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