Peach Twig Borer

Peach twig borer is a major pest in several tree crops. Adult moths have steel gray mottled forewings. Females lay eggs on twigs, fruit, and leaves. Eggs hatch in 4 to 18 days. Larvae are small, brown caterpillars with white intersegmental bands and a black head capsule. They go through four to five instars. Overwintering larvae are sheltered in tiny cells (hibernacula) that they bore under the bark of limb crotches on 1- to 4-year-old wood, or in bark cracks on larger limbs and the trunk. Pupae are dark brown, without a cocoon, and are found in tree crevices, between hull and shell, in curled leaves, or in debris on the ground. There are four generations per year.

Larvae damage both growing shoots and nuts, causing shallow channels and surface grooves on the nutmeat. Peach twig borer damage can be masked by navel orangeworm feeding, which often occurs on nuts previously damaged by peach twig borer.

Some orchards will require a treatment for peach twig borer.

• Use past history, including harvest samples from the previous year, to determine if your orchard will require treatment.
• Preferred treatment timing is during the dormant period (combined with oil sprays if there is concern for San Jose scale, European red mite, or brown almond mites) or at full bloom and petal fall.
• Treatments during the dormant season with environmentally-sound insecticides are acceptable.
• Avoid applications of organophosphates during the dormant season, as these applications threaten water quality when they run off during winter rainfall.
• Be particularly cautious when using insecticides for peach twig borer during bloom, even if it is labeled for this spray timing. Insecticide residues may be picked up in the almond pollen and taken back to the hive by foraging bees where it is fed to bee larvae. The impact of these residues on bee larvae is not fully known. Therefore as a precaution, applications of insecticides during bloom should be avoided until more is known about the impacts on bee larvae. One exception is Bacillus thuringiensis, which can be used safely during bloom when pollinators are present. Bacillus thuringiensis may be combined with bloomtime fungicide sprays, but check restrictions on compatibility.
• Place pheromone traps out around March 15, and monitor for shoot strikes in mid-April to catch any in-season problems.

Peach twig borer has about 30 known species of natural enemies. Among those commonly found in California are the chalcid wasps Copidosoma (=Paralitomastix) varicornis and Euderus (= Hyperteles) lividus. Another commonly found parasite is Macrocentrus ancylivorus, which attacks both peach twig borer and Oriental fruit moth. In some years and orchards, these natural enemies destroy a significant portion of larvae, but they may not reduce twig borer numbers below economically damaging levels. Ants, Formica spp., also can be found preying on peach twig borer larvae.

Use Bacillus thuringiensis at bloom or spinosad (Entrust) as a delayed-dormant treatment or at the May spring timing in an organically certified crop.

Peach twig borer can be successfully managed with environmentally sound insecticides such as spinosyns (Delegate, Entrust, and Success), Bacillus thuringiensis, and chlorantraniliprole (Altacor). Although dormant treatments with organophosphate insecticides are effective and easy to time, they should generally be avoided because of their potential harmful effects on water quality except in orchards where runoff is highly unlikely.

Degree-days

Calculate degree-days for peach twig borer in almond for your location using the peach twig borer pest model. To learn more about using degree-days to time insecticide applications, watch the degree-days video.

Bloom Sprays

To effectively time bloom sprays with Bacillus thuringiensis

• Monitor to determine when larvae are emerging from overwintering hibernacula on limb crotches or on tree trunks.
• Make the first application when 20 to 40% of larvae have emerged.
• Make the second application 7 to 10 days later or when 80 to 100% of larvae have emerged from overwintering hibernacula.
• If emergence is spread out, a third spray may be needed when emergence finally reaches 80 to 100%.

A less-precise method is to apply the first spray between popcorn and full bloom on Nonpareil and a second spray at Nonpareil petal fall, unless there is an extended bloom period, in which case a third application may be needed.

Peach twig borer can be very damaging to developing scaffolds in the second growing season, so a dormant spray is recommended in the first dormant season when monitoring indicates peach twig borer hibernacula.

Spring Sprays

Spring sprays are usually not needed if a dormant spray or the series of Bacillus thuringiensis bloom sprays have been successful, or there is no history of peach twig borer problems. If broad-spectrum insecticides are applied in May, they can cause outbreaks of mites and other secondary pests. Softer pesticides such as spinosad (Entrust, Success), spinetoram (Delegate), and chlorantraniliprole (Altacor) have recently become available that cause less harm to natural enemies.

Place peach twig borer pheromone traps in orchards, one per 20 acres (but never less than two traps in smaller orchards) by March 15. Hang traps 6 to 7 feet high in the northern quadrant of the tree, 1 to 3 feet from the outer canopy. Monitor twice a week; replace pheromone lures at the interval recommended by the manufacturer and replace trap bottoms after 100 moths have been counted and removed or if dust or other debris has accumulated.

If shoot strike monitoring (below) indicates treatment is necessary, use trap catches and degree-days to time a May spray. Optimum timing for first-generation larvae (the May spray) depends on the insecticides used.

• When using spinosyns (Entrust, Success, and Delegate), diamides (Altacor), or organophosphates, apply insecticides at 400 degree-days after the first male is trapped in pheromone traps and moths have been captured on at least two consecutive sampling periods.
• When using an insect growth regulator (Intrepid), make the application at 300 to 400 degree-days.

Accumulate degree-days for peach twig borer using a lower threshold of 50°F and an upper threshold of 88°F.

Monitor trees of any age for shoot strikes in mid-April. Shoot strikes are easiest to see on young trees and on water sprouts. If several strikes are seen in each tree by late April, a spring spray timed with pheromone traps and degree-days may be required. When examining shoot strikes, look for larvae to determine if peach twig borer or oriental fruit moth are the cause of the shoot strikes. Although oriental fruit moth larvae mine deeper into a shoot than peach twig borer larvae, distinguishing the damage can be difficult. Cut the shoot lengthwise to find the larva and identify it: oriental fruit moth larvae are white or pink with a brown head and peach twig borer larvae are dark brown with white portions between each body segment and a black head. Also, peach twig borer shoot strikes occur earlier in the season than do oriental fruit moth strikes.

If navel orangeworm is also a problem, it may be possible to time the May spray to control both pests if navel orangeworm egg hatch occurs at about the same time as the optimum time for the peach twig borer spray. If not, wait and spray the navel orangeworm at hullsplit and time the May spray for peach twig borer. Applying an insecticide during hullsplit for the control of peach twig borer is not as effective as the May spray timing.

	Common name	Amount per acre	REI‡	PHI‡
	(Example trade name)		(hours)	(days)
Pesticide precautions Protect water Calculate VOCs Decision support Protect bees
Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Always read the label of the product being used.
DORMANT
A.	SPINOSAD
	(Entrust)#	1.25–3 oz	4	1
	(Success)	4–10 oz	4	1
	MODE-OF-ACTION GROUP NUMBER1: 5
	COMMENTS: Apply with a dormant oil to suppress overwintering mite and scale populations. Use caution if there is bloom on orchard floor vegetation that is being visited by pollinators.
B.	SPINETORAM
	(Delegate WG)	1.5–3.5 oz	4	1
	MODE-OF-ACTION GROUP NUMBER1: 5
	COMMENTS: Apply with a dormant oil to suppress overwintering mite and scale populations. Apply at night to avoid foraging bees that may be present on blooming groundcover.
C.	DIFLUBENZURON
	(Dimilin 2L)*	12–16 oz	12	28
	MODE-OF-ACTION GROUP NUMBER1: 15
	COMMENTS: Apply at a volume sufficient to ensure good coverage. Use with a narrow range oil at 1.5 to 4% by volume, but do not use oil on water-stressed trees or following periods of dry winds.
D.	CHLORANTRANILIPROLE (RYNAXYPYR)
	(Altacor)	3–4.5 oz	4	10
	MODE-OF-ACTION GROUP NUMBER1: 28
	COMMENTS: Apply with a narrow range oil to suppress overwintering mite and scale populations.
E.	ACETAMPRID
	(Assail 30SG)	5.3–9.6 oz	12	14
	MODE-OF-ACTION GROUP NUMBER1: 4A
	COMMENTS: Apply with a narrow range oil to suppress overwintering mite and scale populations. Use caution if there is bloom on orchard floor vegetation that is being visited by pollinators.
F.	ESFENVALERATE
	(Asana XL)*	9.6–19.2 oz	12	21
	MODE-OF-ACTION GROUP NUMBER1: 3A
	COMMENTS: Residue has been shown to harm predatory mites into the growing season. When widely used in a watershed, runoff following rainfall events may result in its presence in surface waters at levels that violate federal and state water quality standards.
G.	BIFENTHRIN
	(Brigade WSB)*	8.0–32.0 oz	12	7
	MODE-OF-ACTION GROUP NUMBER1: 3A
	COMMENTS: Pyrethroid insecticides have a broad spectrum of activity against nontarget organisms. When Brigade is widely used in a watershed, runoff following rainfall events may result in its presence in surface waters at levels that violate federal and state water quality standards.
H.	CYFLUTHRIN
	(Baythroid XL)*	2.4–2.8 oz	12	14
	MODE-OF-ACTION GROUP NUMBER1: 3A
	COMMENTS: Pyrethroid insecticides have a broad spectrum of activity against nontarget organisms. When Baythroid is widely used in a watershed, runoff following rainfall events may result in its presence in surface waters at levels that violate federal and state water quality standards.
I.	LAMBDA-CYHALOTHRIN
	(Warrior II with Zeon)*	1.28–2.56 fl oz	24	14
	MODE-OF-ACTION GROUP NUMBER1: 3A
	COMMENTS: Pyrethroid insecticides have a broad spectrum of activity against nontarget organisms. When Warrior is widely used in a watershed, runoff following rainfall events may result in its presence in surface waters at levels that violate federal and state water quality standards.
DELAYED-DORMANCY OR PINK BUD
A.	METHOXYFENOZIDE
	(Intrepid 2F)	8–16 fl oz	4	14
	MODE-OF-ACTION GROUP NUMBER1: 18
	COMMENTS: Apply in sufficient water to ensure good coverage. Apply with Latron or similar surfactant at 0.125% volume by volume.
B.	DIFLUBENZURON
	(Dimilin 2L)*	12–16 fl oz	12	28
	MODE-OF-ACTION GROUP NUMBER1: 15
	COMMENTS: Apply in sufficient water to ensure good coverage. Apply with Latron or similar surfactant at 0.125% volume by volume. Avoid use when honey bees are already present in the orchard.
C.	CHLORANTRANILIPROLE (RYNAXYPYR)
	(Altacor)	3–4.5 oz	4	10
	MODE-OF-ACTION GROUP NUMBER1: 28
	COMMENTS: Apply with a dormant oil to suppress overwintering mite and scale populations.
BLOOM
Note: Additional insecticides are labeled for use during bloom. However, due to concerns over pollinator safety (adult, developing brood in the hive, or both), applications of other insecticides by themselves or in combination with fungicides should be delayed until bloom is complete and hives are removed.
A.	BACILLUS THURINGIENSIS ssp. KURSTAKI#
	(various products)	Label rates	4	0
	MODE-OF-ACTION GROUP NUMBER1: 11A
	COMMENTS: Best if applied by ground, because thorough coverage of the shoot tips is essential. If it must be applied by air because of wet ground or other factors that preclude ground spray, fly about 20 ft over the tree canopy to allow better spray deposition on treetops. Make two applications during bloom: the first between popcorn and full bloom on Nonpareil, and the second at Nonpareil petal fall. A third Bacillus thuringiensis spray may be needed in cool and wet years when peach twig borer emergence is extended. Compatible with fungicide sprays. Will not control San Jose scale, European red mite eggs or other pests normally controlled with oil sprays during the dormant or delayed-dormant periods.
SPRING
A.	CHLORANTRANILIPROLE (RYNAXYPYR)
	(Altacor)	3.0–4.5 oz	4	10
	MODE-OF-ACTION GROUP NUMBER1: 28
B.	SPINETORAM
	(Delegate WG)	3–7 oz	4	1
	MODE-OF-ACTION GROUP NUMBER1: 5
	COMMENTS: Apply at night to target active adult moths and to avoid foraging bees that might be present on foraging groundcover. May be disruptive of predaceous thrips and some parasitoids.
C.	EMAMECTIN BENZOATE
	(Proclaim)*	3.2–4.8 oz	See label	14
	MODE-OF-ACTION GROUP NUMBER1: 6
D.	SPINOSAD
	(Entrust)#	1.25–3 oz	4	1
	(Success)	4–10 oz	4	1
	MODE-OF-ACTION GROUP NUMBER1: 5
	COMMENTS: A fermentation-derived insect control product. May be disruptive of predaceous thrips and some parasitoids.
E.	BACILLUS THURINGIENSIS ssp. KURSTAKI#
	(various products)	Label rates	4	0
	MODE-OF-ACTION GROUP NUMBER1: 11A.
	COMMENTS: Make two applications: one at 300 to 350 DD from biofix and the other at 450 to 500 DD. Compatible with fungicide sprays and can be tank mixed with them. Good coverage is essential. Ground application using a concentrate rate (80–100 gal water maximum) is preferred.
F.	ACETAMPRID
	(Assail 30SG)	5.3–9.6 oz	12	14
	MODE-OF-ACTION GROUP NUMBER1: 4A

*	Permit required from county agricultural commissioner for purchase or use.
‡	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.
#	Acceptable for use on organically grown produce.
1	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; pesticides with a 1B group number should be alternated with pesticides that have a group number other than 1B. Mode-of-action group numbers are assigned by IRAC (Insecticide Resistance Action Committee).

• Degree-day calculator
• Degree-day table
• Harvest sample
• Monitor hibernacula
• Monitor shoot strikes in spring
• Pheromone Traps
• Using degree-days to time insecticide applications