How to Manage Pests

UC Pest Management Guidelines

Apricot

Mealy Plum Aphid

Scientific Name: Hyalopterus pruni

(Reviewed 10/14, updated 10/14)

In this Guideline:


DESCRIPTION OF THE PEST

Wingless adult aphids are pale green with three dark green longitudinal stripes on their backs. Their bodies are covered with a white, mealy wax. The winged form has a dark thorax and transverse bands on the abdomen. After overwintering in the egg stage near the bases of buds, eggs hatch during bloom and wingless adults develop. Winged adults appear in June and July, as warm weather approaches, and migrate to reed grass or cattails. In fall, winged adults return to apricot trees where wingless females develop and mate with winged male aphids; the overwintering eggs are laid soon after.

DAMAGE

Vegetative growth on the trees may be stunted by high aphid numbers, but the principal damage caused by mealy plum aphid is the development of the black sooty mold that grows on the aphid's honeydew.

MANAGEMENT

Several natural enemies are important in the control of aphids in the orchard, but large aphid numbers may require pesticide application. Generally small pockets of infestations appear in an orchard before any significant damage occurs on the fruit, allowing time to treat the orchard during the following dormant period. Spring treatments may also be made.

Biological Control

Important predators include lady beetles (especially the multicolored Asiatic lady beetle, Harmonia axyridis), green and brown lacewings, syrphid flies, and soldier beetles. However, these predators do not adequately control large numbers of mealy plum aphids.

Organically Acceptable Methods

Use biological control and sprays of neem oil on organically grown apricots.

Monitoring and Treatment Decisions

Chemical control of the mealy plum aphid on apricot is seldom necessary. If they were a problem the previous season, eggs are easily killed by insecticide sprays in the fall, before leaf fall and before the beginning of the rainy season. Treatments near or during seasonal rains may cause pesticides to runoff into water bodies.

Dormant oil treatments are recommended during dormancy, when aphids start to hatch. Aphid eggs are not susceptible to oil sprays. Because it is difficult to time sprays with hatching, oil has to be applied several times during the dormant season. Some apricot cultivars are sensitive to dormant oil sprays. Parasites, if directly contacted by oil sprays may be affected, but parasite habits, such as searching for hosts on the underside of leaves, reduce that chance greatly. Furthermore, predators are more important in the management of the mealy plum aphid.

Dormant monitoring

If the fall treatment is not applied, be sure to monitor during dormancy. (For more information, see DORMANT SPUR SAMPLE.) If dormant monitoring indicates treatment is necessary, two applications of oil at bloom can be used. Parasites are not active at bloom, and therefore are not affected by the bloom oil sprays.

Spring monitoring

If a dormant or delayed dormant pesticide application was not applied or if application was unsuccessful, monitor mealy plum aphid in spring and repeat pesticide applications in early May when aphids are present. Follow the monitoring guidelines in SPRING/SUMMER MONITORING to determine if treatment is necessary.

Common name Amount to Use** REI‡ PHI‡
(Example trade name) (conc.) (dilute)
(hours) (days)

UPDATED: 10/14
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.
 
FALL
 
A. PHOSMET
  (Imidan 70-W) 2.125–4.25 lb 1 lb 7 days 14
  MODE-OF-ACTION GROUP NUMBER1: 1B
  COMMENTS: Apply with a buffer to lower solution pH to 5.0. Causes less harm to beneficials and water quality than other materials listed. When applied early in the dormant season, this low-label rate provides effective control and reduces the risk of runoff into waterways, mitigating concerns of surface water pollution. Early applications may not be effective for peach twig borer.
 
B. DIAZINON*
  (Diazinon 50W) 1 lb/100 gal 4 days 21
  MODE-OF-ACTION GROUP NUMBER1: 1B
  COMMENTS: Organophosphate insecticides used during delayed dormancy are very toxic to honey bees. Remove bees from orchard if cover crops or weeds are in bloom. Apply diazinon only during dormant or delayed dormant period and do not allow meat or dairy animals to graze in treated orchards When applied early in the dormant season, this low-label rate provides effective control and reduces the risk of runoff into waterways, mitigating concerns of surface water pollution. Levels in surface waters of this material that are high enough to be toxic to some aquatic invertebrates have occurred following rains in January and February; avoid runoff into surface waters. Early applications may not be effective for peach twig borer. Do not apply more than 4 lbs product per application.
 
C. ESFENVALERATE*
  (Asana XL) 4.8–14.5 fl oz 2–5.8 fl oz 12 14
  MODE-OF-ACTION GROUP NUMBER1: 3A
  COMMENTS: This lower-than-label rate and early timing provide effective control and reduce the risk of runoff into waterways, mitigating concerns of surface water pollution. Pyrethroid residues remaining on bark will continue to affect mite predators long after application, increasing potential for spider mite infestations. Lower rates, early timing, or both may not be effective for peach twig borer and are not effective for San Jose scale control. Do not apply more than 14.5 fl oz product/acre per treatment.
 
D. THIAMETHOXAM
  (Actara) 3–4 oz 0.75–1 oz 12 14
  MODE-OF-ACTION GROUP NUMBER1: 4A
  COMMENTS: Do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging, because direct treatment or residues on blooming crops and weeds are highly toxic to bees. Remove (mow, disc, etc.) blooming ground cover before treatment. Apply prebloom or postbloom but not from swollen bud to petal fall. Do not apply less than 2 oz or more than 5.5 oz/acre per application or exceed 8 oz/acre per season. This chemical is listed on the EPA reduced risk to the environment. Repeat applications of any neonicotinoid insecticide (imidacloprid-Admire; thiamethoxam-Actara) can lead to resistance to all neonicotinoids. Alternate neonicotinoids with an insecticide that has a different mode of action to help delay the development of resistance.
 
E. IMIDACLOPRID
  (Admire Pro –foliar application) 1.4–2.8 fl oz 12 0
  MODE-OF-ACTION GROUP NUMBER1: 4A
  COMMENTS: Do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging, because direct treatment or residues on blooming crops and weeds are highly toxic to bees. Remove (mow, disc, etc.) blooming ground cover before treatment. Do not apply less than 10 days prior to prebloom. Repeat applications of any neonicotinoid insecticide (imidacloprid-Admire; thiamethoxam-Actara) can lead to resistance to all neonicotinoids. Alternate neonicotinoids with an insecticide that has a different mode of action to help delay the development of resistance.
 
DORMANT or DELAYED DORMANT/BLOOM
 
A. NARROW RANGE OIL# 4 gal 12 0
  MODE OF ACTION: Contact including smothering and barrier effects.
  COMMENTS: Apply in 100 gal water/acre. Oil must contact aphids to provide control. Apply at green tip or popcorn to kill the hatching aphids (hatch generally occurs in early March). Some of the new lower-chilling varieties, especially Poppycot, can be highly susceptible to oil damage. Use extreme care when applying oil to these varieties. May be tank mixed with bloom time treatments aimed at peach twig borer and brown rot. Make a second application 10 days later. This usually coincides with full bloom in most years.
 
SPRING
 
A. NEEM OIL#
  (Trilogy) 1–2% 4 0
  MODE OF ACTION: Unknown. A botanical insecticide.
  COMMENTS: Repeat applications may be necessary.
 
B. FLONICAMID
  (Beleaf) 2.0–2.8 oz 0.6 fl oz 12 14
  MODE-OF-ACTION GROUP NUMBER1: 9C
   
C. NARROW RANGE OIL# 6–8 gal 12 0
  MODE OF ACTION: Contact including smothering and barrier effects.
  COMMENTS: Apply in 200 gal water/acre. Oil must contact aphids to provide control. Harmful to aphid parasites. Apricot trees tolerate oil treatments better in spring than during full dormancy. Do not apply oil within 2 weeks of Captan or within 30 days of a sulfur treatment. Not all oils are organically acceptable; be sure to check individual products.
 
D. SPIROTETRAMAT
  (Movento) 6–8 oz 1.25-2.25 oz 24 7
  MODE-OF-ACTION GROUP NUMBER1: 23
  COMMENTS: Must be applied with an adjuvant to improve penetration. Do not apply before bloom, during bloom, or 10 days after petal fall. Toxic to predatory mites.
 
E. IMIDACLOPRID
  (Admire Pro –foliar application) 1.4–2.8 fl oz 12 0
  MODE-OF-ACTION GROUP NUMBER1: 4A
  COMMENTS: Do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging, because direct treatment or residues on blooming crops and weeds are highly toxic to bees. Repeat applications of any neonicotinoid insecticide (imidacloprid-Admire) can lead to resistance to all neonicotinoids. Alternate neonicotinoids with an insecticide that has a different mode of action to help delay the development of resistance.
 
F. DIAZINON*
  (Diazinon 50W) 1 lb/100 gal 4 days 21
  MODE-OF-ACTION GROUP NUMBER1: 1B
  COMMENTS: Avoid drift and tailwater runoff into surface waters. Where apricots are grown adjacent to waterways, do not use this material. Do not apply more than 4 lbs product per application.
 
** For concentrate applications, 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 400 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 two intervals is the minimum time that must elapse before harvest.
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 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 website at http://www.irac-online.org/.
* Permit required from county agricultural commissioner for purchase or use.
# Acceptable for use on organically grown produce.
Not recommended or not on label.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Apricot
UC ANR Publication 3433

Insects and Mites

W. W. Coates, UC Cooperative Extension, San Benito County
R. A. Van Steenwyk, Insect Biology, UC Berkeley
W. J. Bentley, UC IPM Program, Kearney Agricultural Center, Parlier
K. R. Day, UC Cooperative Extension, Tulare County
K. A. Kelley, UC Cooperative Extension, Stanislaus County
J. L. Caprile, UC Cooperative Extension, Contra Costa County

Acknowledgment for contributions to Insects and Mites:
L. C. Hendricks, UC Cooperative Extension, Merced County

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