How to Manage Pests

UC Pest Management Guidelines

Walnut

Codling Moth

Scientific Name: Cydia pomonella

(Reviewed 12/07, updated 8/13)

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 flight of moths 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 60 eggs on leaves or nuts. Eggs are disc 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. The larvae when fully grown 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. At harvest 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. 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 with 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 depend on the size of the trees and the degree of codling moth infestation. In all cases, a program of monitoring with pheromone (codlemone) and/or pheromone+kairomone (known as CM-DA combo) and checking for damage is necessary to follow codling moth generations and assess the degree of infestation and 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

Alone, natural enemies are not able to keep codling moth populations 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 with phytotoxicity with oils, especially when weather is hot, and oils have 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 1 mg (1X) lure traps, 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 populations. 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

Three types of pheromone mating disruption products are 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.
  • Plastic (hand-applied) dispensers of various sorts – 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.

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 codling moth populations. It is less effective in orchards with susceptible varieties (e.g., Ashley, Payne, Serr, Vina) or in orchards that have a large codling moth population history or a previous history of 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 population levels.

Air currents entering the windward sides of orchards adjacent to open areas may break down 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

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

Place CM-DA combo traps in the mid-canopy of trees at a rate of 1 trap per 25 acres. High counts of codling moths in these traps will help determine the need for supplementing mating disruption with insecticides.

Hang a smaller number of standard 1-mg traps (1 trap per 50 acres or per block) traps 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 chemical treatments may be necessary.

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

Setting Out Mating Disruptants

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

Sprayable pheromone should be applied at or after biofix when leaves have started growing and are partially expanded. Sprayable formulations have short residual activity and must be applied at 3- to 4-week intervals for sustained mating disruption. Research to date has not shown a benefit from applications applied at longer intervals. Make additional applications shortly after the biofix of the second and third flights. When large populations exist in an orchard, sprayable pheromones have been shown to reduce codling moth damage when added to a conventional spray program. As with plastic 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 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 following 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 to plan for next year.

Supplemental Treatments

When making the transition from managing codling moth with insecticides to mating disruption in orchards with high codling moth populations (i.e., where damage in the previous season's harvest sample was over 4%), supplement mating disruption with insecticide applications to reduce the population. In the second year or in orchards with moderate populations (i.e., where the previous season's damage was 2 to 4% at harvest), supplement mating disruption with sprays of insecticides that will not disrupt populations of natural enemies. In orchards with low populations (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 time applications for maximum effectiveness, which is when the larvae are emerging from the eggs.

MONITORING AND TREATMENT DECISIONS IN A CONVENTIONAL ORCHARD

In orchards treated with contact or ingested insecticides (e.g., spinosad and oil, organophosphates, pyrethroids, and carbamates), time all treatments to kill larvae as they emerge from eggs. If insect growth regulators are used, apply treatments before egg laying (Dimilin) or egg hatch (Confirm, Intrepid), depending on label instructions. Use pheromone 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.) 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.

Treatment Decisions

The need for treatment and the timing of sprays is different for the different generations of codling moth.

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 treatments, it is best to delay treatment 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 2 moths per trap per night are being caught with 1 mg traps, delay treatment until the second flight peak (1B). If you see an increase in trap catches, treat when 600 to 700 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, plan to treat both the 1A and 1B larvae:

Treating 1A larvae

Apply a treatment when 300 DD 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 DD 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 treatment materials are listed in the Treatment Table. 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 populations decline to below damaging numbers 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 a treatment for second-generation larvae, determine the biofix for the second generation. This generally occurs around 1060 DD from the first biofix point. However, any increase in trap catches after 800 DD can be considered the biofix. To better determine this biofix, clean and service the traps around 700 DD 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 treatment. All codling moth damaged nuts drop except when there is a second peak of the first flight or if the weather is not hot enough. (Look for frass at the blossom end of nuts to confirm that codling moth caused the drop.) 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). 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 DD from the second biofix and use a short residual pesticide. If you collect more than 24 codling moth-damaged nuts per tree, apply a treatment as soon as eggs of the second generation start hatching (250 DD 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 treat 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/trap/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 DD have accumulated from biofix.
Moderate to high populations If damage exceeded 3% the previous season or more than an average of 2 moths/trap/night are beingcaught with 1 mg traps, treat both the 1A and 1B larvae.
First treatment (1A)1 Spray at 300 DD2 from first flight biofix or when small nutlets first appear, whichever is later.
Second treatment (1B)1

Look for 2nd peak about 600–700 DD from 1st biofix by checking traps frequently.

If a second peak occurs, spray when residual effectiveness of 1st treatment ends.

SECOND FLIGHT Determine 2nd biofix to time sprays for second-generation egg hatch.

Use trap catch data to detect resumption of moth flight activity and establish biofix. The 2nd biofix will be when an increase occurs in trap catches between 800–1300 DD from 1st biofix (average is 1060 DD).

Begin accumulating degree-days from 2nd 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/10 trees at least 10 ft 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 2nd biofix and use short residual insecticide.

If there is more than 5% infestation in visual inspection, spray at 250 DD2 from 2nd biofix and use long residual pesticide to cover entire hatch period (about 1 month).

Monitoring nut drop If there is no 2nd 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 4–24 infested nuts/tree, spray at 250 DD from 2nd biofix and use short residual insecticide.

If there are more than 24 infested nuts/tree, spray at 250 DD from 2nd 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 800–1300 DD from 2nd 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 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 3rd 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 4th 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
2 Timing is 50-100 DD earlier for growth regulators

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

For the third and fourth generation, the decision to treat must be based on a combination of factors including previous treatments, number of nuts infested in the previous generation, trap catches, and the ability to harvest early. To determine the numberof 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 treat. If greater than 2% are infested, treat.

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 DD from the second biofix and for the fourth biofix around 1200 DD from the third biofix (the range for both biofix points is 800 to 1300 DD). Treatments are often not needed at this time; but if stings are found on nuts, apply sprays 300 DD after the biofix.

Common name Amount to use** R.E.I.‡ P.H.I.‡
(trade name) (conc.) (dilute)
(hours) (days)

  Calculate impact of pesticide on air quality
 
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.
 
Residual periods mentioned in the COMMENT sections 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 (more than 10 acres for plastic dispensers or sprayable formulations, more than 40 acres for aerosol dispensers) that have a squarish shape and low to moderate codling moth populations, with trees of uniform size and moderate height. 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#
 
  Isomate-CM Mist 1 dispenser/1.5–2 acres 0 Up to 200
  Checkmate Puffer CM-O 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. In many situations, this will result in an overall density slightly greater than one per 2 acres. The use of aerosol dispensers at this density has been successfully demonstrated in orchards 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 populations. 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 population and activity.
 
Plastic (hand-applied) dispensers#
 
  Isomate-C Plus 400 dispensers/acre 0 160+
  Isomate-CTT 200 dispensers/acre 0 160+
  Isomate-CM Ring 20–40 dispensers/acre 0 160+
  CheckMate CM-XL1000 200 dispensers/acre 0 160+
  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. Do not apply more than 36.2 fl oz CheckMate CM-F/acre/year.
 
INSECTICIDE CONTROLS
 
High Populations Only
 
A. METHYL PARATHION*
  (Penncap-M) 6–8 pt 1.5–2 pt 25 days 14
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: This material has a residual activity of about 20 days and is very effective against organophosphate (Guthion)- and pyrethroid-resistant codling moths. Repeated applications of this material will reduce resistance levels. However, this material is extremely toxic to honey bees. Do not apply when weeds or cover crops in orchard are in bloom or have flower buds and bees are actively foraging in areas to be treated. Nor should it be applied during nonforaging hours (including nighttime) if bees have been foraging during the day. Minimum spray interval is 21 days. Available for use under a special local needs registration. Do not apply more than 32 pt/season or allow livestock to graze treated areas. Note: All sales of this product have been cancelled and all uses must end by December 31, 2013.
 
Moderate to High Populations
 
A. SPINETORAM
  (Delegate) 4.5–7 oz 4 1
  MODE OF ACTION GROUP NUMBER1: 5
  COMMENTS: Larvicide. The best time to apply is at egg hatch. Do not apply more than 0.438 lb a.i. (28 oz)/acre/year. 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. Do not apply more than 0.2 lb a.i. (9 oz)/acre/year. 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. LAMBDA-CYHALOTHRIN*
  (Warrior II with Zeon) 2.56 fl oz 24 14
  MODE OF ACTION GROUP NUMBER1: 3
  COMMENTS: Larvicide. Residual at the acre rate is about 21 days. Do not apply more than 0.16 lb a.i. (0.64 pt)/acre per year. Do not apply more than 0.12 lb a.i. (0.48 pt)/acre/year post bloom. 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%.
 
D. CYFLUTHRIN*
  (Baythroid XL) 2–2.4 fl oz 0.5–0.6 fl oz 12 14
  MODE OF ACTION GROUP NUMBER1: 3
   
E. BIFENTHRIN*
  (Brigade WSB) 8–32 oz 2–8 oz 12 7
  MODE OF ACTION GROUP NUMBER1: 3
  COMMENTS: Provides about a 21- to 28-day residual at the high label rate.
 
Moderate Populations
 
A. ACETAMIPRID
  (Assail 70WP) 4.0–8.0 oz 0.271–1 oz 12 14
  MODE OF ACTION GROUP NUMBER1: 4A
  COMMENTS:
 
B. FLUBENDIAMIDE
  (Belt SC) 3–4 oz 0.75–1 oz 12 14
  MODE OF ACTION GROUP NUMBER1: 28
  COMMENTS: Do not apply more than 12 fl oz/acre/crop season.
 
C. EMAMECTIN BENZOATE*
  (Proclaim 5SG) 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. Do not apply more than 14.4 oz/acre/season.
   
D. 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. Do not apply more than 8.5 lb/acre/application or more than 5 times/season. Buffer to a pH of 5.5–6.0.
 
E. CHLORPYRIFOS*
  (Lorsban 4E) 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 populations are moderate. Effective against Guthion- and pyrethroid-resistant populations. When codling moth trap catches are in the mid- to high range, 2 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 2 applications/season, most effective control results if both applications are directed at the same egg hatch period, either in the 1st or 2nd generation. Provides control of the hyperparasite that attacks the aphid parasite Trioxys pallidus. Levels in surface waters of this material that are high enough to be toxic to certain aquatic invertebrates have occurred following rains; avoid runoff into surface waters. Do not make more than 2 applications/season. Do not allow livestock to graze in treated areas.
 
F. METHOXYFENOZIDE
  (Intrepid 2F) 16–24 fl oz 4 14
  MODE OF ACTION GROUP NUMBER1: 18A
  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 DD after the first biofix. Do not apply more than 24 fl oz/acre/application or more than 64 fl oz/acre/season.
 
G. ESFENVALERATE*
  (Asana XL) 9.6–19.2 fl oz 4 fl oz 12 21
  MODE OF ACTION GROUP NUMBER1: 3
  COMMENTS: Residual of about 14–21 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 material is not effective on scales, so if you have a scale problem choose another chemical. Do not apply more than 0.2 lb a.i./acre/season.
 
H. PERMETHRIN
  (Ambush) 0.2–0.4 lb a.i. 0.05–0.1 lb a.i. 12 1
  (Pounce)* 0.2–0.25 lb a.i. 0.05­–0.0625 lb a.i. 12 1
  MODE OF ACTION GROUP NUMBER1: 3
  COMMENTS: Residual of about 14–21 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 treated 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 this material is used. This material is best used later in the season.
 
Low Populations
 
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 populations. Coverage is extremely important: it is not recommended for the 1st 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. This material must be applied earlier than the other materials because it needs to be on the leaf before eggs are laid. Treatment timing is before the start of the 2nd generation fight, which is about 800–900 DD from the 1st biofix and before the start of the 3rd generation flight, which is 1800–1900 DD from the 1st biofix. This material is not a stand-alone material and should be used in combination with another control. Do not make more than 3 applications/season or apply more than 48 fl oz/season.
 
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 DD; larvae must ingest to become infected by this virus. Make a second application 7 to 10 days later, a third application at 600 DD, 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 material 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 50-60% of population. Do not use more than 9 oz. of Entrust per acre per crop. Do not apply treatments less than 7 days apart. Limited field experience 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 additional information, see their Web site at http://www.irac-online.org/.
** For concentrate application, use the amount given in 80–100 gal water/acre, or lower if the label allows; for dilute application, amount is per 100 gal water to be applied in 300–500 gal water/acre, according to label.
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 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.
Not recommended or not on label.
NA Not applicable.

IMPORTANT LINKS

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Walnut
UC ANR Publication 3471

Insects and Mites

  • C. Pickel, UC IPM Program/UC Cooperative Extension, Sutter/Yuba counties
  • J. A. Grant, UC Cooperative Extension, San Joaquin County
  • W. J. Bentley, UC IPM Program/Kearney Agricultural Center, Parlier
  • J. K. Hasey, UC Cooperative Extension, Sutter/Yuba counties
  • W. W. Coates, UC Cooperative Extension, San Benito County
  • R. A. Van Steenwyk, Insect Biology, UC Berkeley
Acknowledgment for contributions to Insects and Mites:
  • W. H. Olson, UC Cooperative Extension, Butte County
  • L. C. Hendricks, UC Cooperative Extension, Merced County
  • G. S. Sibbett, UC Cooperative Extension, Tulare County
Acknowledgment for contributions to Codling Moth:
  • D. Light, USDA, Albany, CA

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