Description of the Pest
Newly hatched rosy apple aphids are dark green and are found on new growth in early spring. Mature rosy apple aphids, clustering in curled leaves or on young fruits in spring, are purplish and covered with a waxy, powdery bloom. Winged forms develop on apple trees in late spring and migrate to plantain, where they are found in summer. In fall, winged forms develop and migrate back to the apple trees. Overwintering eggs are laid on fruit spurs and shoots of the apple trees; they are shiny, black, and elongated.
Damage
This is potentially the most damaging aphid species on apples. Rosy apple aphids cluster on leaves of fruit spurs and growing shoots where they cause severe leaf curling. Fruits on heavily infested fruit spurs fail to properly develop and become misshapen.
Management
Rosy apple aphid numbers vary considerably from year to year; this aphid is not a pest every year. Like many aphids, rosy apple aphid spends part of the growing season on alternate host plants. The most common host is buckhorn plantain, Plantago lanceolata, also known as ribgrass. Other hosts are P. major and P. rugelii. Do not allow these weeds to grow in your cover crop. These species often become a problem when you mow rather than cultivate. Monitor for eggs during the dormant season to determine need for treatment.
Biological Control
There are many natural enemies that feed on rosy apple aphids; however, fruit size may be reduced before natural enemies bring the aphids under control. Among the important predators are lady beetles, green lacewings, brown lacewings, syrphid fly larvae, and soldier beetles. Inseason sprays (even soap sprays) applied to control rosy apple aphid can kill natural enemies, allowing rosy apple aphid populations to increase.
Organically Acceptable Methods
Biological control, approved narrow range oil sprays, and the use of azadirachtin (Neemix) are organically acceptable.
Monitoring and Treatment Decisions
During the dormant season collect 25 to 100 fruit spurs from various parts of trees throughout the block. Using a hand lens, examine the spurs for rosy apple aphid eggs. This can be done in conjunction with the dormant European red mite sample. Although difficult to detect, if any eggs are found, a dormant treatment is required because aphid colonies may quickly spread over the tree. Treat nonbearing trees to prevent stunting of terminal shoots. Because overwintering eggs are located on the bark, delayed dormant application will greatly reduce populations. Young trees need to be treated when terminals are infested; mature trees can tolerate more damage. Codling moth sprays should be chosen with aphid control in mind.
| Common name | Amount per acre** | REI‡ | PHI‡ | |||
|---|---|---|---|---|---|---|
| (Example trade name) | (conc.) | (dilute) | (hours) | (days) | ||
| 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 AND DELAYED DORMANT | ||||||
| A. | NARROW RANGE OIL | |||||
| (415, 440) | 6% solution | 2% solution | 4 | 0 | ||
| MODE OF ACTION: Contact including smothering and barrier effects. | ||||||
| COMMENTS: Organic growers should apply dormant flowable emulsion during delayed dormant to silver tip stage to get any control of rosy apple aphid. | ||||||
| B. | NARROW RANGE OIL | |||||
| (415, 440) | 2% solution | 2% solution | See label | 0 | ||
| MODE OF ACTION: Improves translaminar movement and insecticide persistence. | ||||||
| . . . PLUS . . . | ||||||
| DIAZINON | ||||||
| (Diazinon 50W) | 4 lb | 1 lb | 4 days | 21 | ||
| MODE-OF-ACTION GROUP NUMBER1: 1B | ||||||
| COMMENTS: Avoid drift and runoff into surface waters or choose alternative materials. Diazinon has been found in surface waters at levels that violate federal and state water quality standards. Highly toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging. | ||||||
| SPRING FOLIAGE SPRAY | ||||||
| A. | SPIROTETRAMAT | |||||
| (Movento) | 6–9 fl oz | 24 | 7 | |||
| MODE-OF-ACTION GROUP NUMBER1: 23 | ||||||
| COMMENTS: Do not apply until after petal fall. Allow 14 days between applications. Maximum is 25 fl oz/acre (0.4 lb a.i./acre) per crop per season. | ||||||
| B. | IMIDACLOPRID | |||||
| (Admire Pro) | 2.8 fl oz | 12 | 7 | |||
| MODE-OF-ACTION GROUP NUMBER1: 4A | ||||||
| COMMENTS: Apply before leaf curling starts. Repeat applications of any neonicotinoid insecticide (acetamiprid-Assail; imidacloprid-Admire Pro; thiamethoxam –Actara) can lead to resistance to all neonicotinoids. Alternate neonicotinoids with an insecticide that has a different mode-of-action Group number to help delay the development of resistance. To help prevent development of resistance, do not use for both codling moth and aphid control. Highly toxic to bees. Review and follow the California neonicotinoid regulations effective January 1, 2024. Permissible application rates of this insecticide may be lower than label rates if applying more than one neonicotinoid active ingredients or using more than one application method in the same season. |
||||||
| C. | ACETAMIPRID | |||||
| (Assail 70 WP) | 1.1–1.7 oz | 12 | 7 | |||
| MODE-OF-ACTION GROUP NUMBER1: 4A | ||||||
| COMMENTS: May cause outbreaks of mites, especially in orchards with chronic mite problems; addition of 1% oil (volume by volume) and limiting applications to a single application may help mitigate mite problems. Repeat applications of any neonicotinoid insecticide (acetamiprid-Assail and imidacloprid- Admire Pro) 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. To help prevent development of resistance, do not use for both codling moth and aphid control. Toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging. | ||||||
| D. | DIAZINON* | |||||
| (Diazinon 50W) | 4 lb | 1 lb | 96 (4 days) | 21 | ||
| MODE-OF-ACTION GROUP NUMBER1: 1B | ||||||
| COMMENTS: Foliage treatments are important for young trees with severe infestations. Applications made during the foliage season are very disruptive to beneficials. Codling moth sprays will normally control aphids. Avoid drift and tailwater runoff into surface waters. | ||||||
| E. | NARROW RANGE OIL# | |||||
| (JMS Stylet Oil, Omni) | Label rates | See label | 0 | |||
| MODE OF ACTION: Contact including smothering and barrier effect. | ||||||
| COMMENTS: Apply as soon as colonies are found and reapply at 7- to 10-day intervals as long as active colonies are found. | ||||||
| F. | NARROW RANGE OIL# | |||||
| (JMS Stylet Oil, Omni) | Label rates | See label | 0 | |||
| MODE OF ACTION: Improves translaminar movement and insecticide persistence. | ||||||
| . . . PLUS . . . | ||||||
| AZADIRACHTIN# | ||||||
| (Neemix 4.5) | Label rates | 4 | 0 | |||
| MODE-OF-ACTION GROUP NUMBER1: un | ||||||
| COMMENTS: Apply as soon as colonies are found and reapply at 7- to 10-day intervals as long as active colonies are found. Azadirachtin without oil is not effective in controlling this pest. | ||||||
| ** | For dilute application, rate is per 100 gal water to be applied in 300 to 500 gal water/acre, according to label; for concentrate applications, use 80 to 100 gal water/acre or lower if the label allows. |
| ‡ | 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. |
| * | Permit required from county agricultural commissioner for purchase or use. |
| # | Acceptable for use on organically grown produce. |
| 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 ("un"=unknown or uncertain mode of action) are assigned by IRAC (Insecticide Resistance Action Committee). |