Agriculture: Floriculture and Ornamental Nurseries Pest Management Guidelines

Aphids

  • Green peach aphid: Myzus persicae
  • Melon aphid: Aphis gossypii
  • Description of the Pest

    Aphids develop through three life stages : adult, egg, and nymph. Adults and nymphs are oblong to pear-shaped, soft-bodied insects that suck phloem sap. At maturity, most species have a body length of 1/25 to 1/12 inch (1–2 mm). Species that feed openly on foliage are distinguished by the presence of cornicles, a pair of tubelike, rear-pointing appendages on top the abdomen. Root-feeding aphids and those that feed within wax they secrete on foliage and shoots commonly lack obvious cornicles. Eggs hatch within adult females most of the growing season, and generally can be observed only during fall on deciduous perennials where aphids overwinter in the egg stage.

    Numerous species of aphids feed on flower and nursery crops. Some are host-specific; these generally feed on only one or a few kinds of plants. Some host-specific aphids migrate seasonally between different hosts or plant parts or both, such as feeding on foliage of their deciduous host during spring through fall and overwintering on the roots of a conifer host. Consult Aphids on the World's Plants: An Online Identification and Information Guide for more information, including complete lists of each species' known host plants. The most common pest species are the cotton, or melon, aphid and green peach aphid, each having over 200 plant hosts.

    Identifying the particular aphid species present can be important for reasons including

    • Differences in susceptibility to certain pesticides.
    • Different host plants, including weeds, that can help maintain a population.
    • Differences in biology, which may offer clues on management.
    • Their role as virus vectors between susceptible crops and weeds that hosts those viruses. Note that some viruses can be moved in other ways, such as on contaminated propagation and pruning tools.

    Green peach and cotton (melon) aphids are generally the most common pest species in floriculture and nurseries. They can be distinguished using a hand lens or other magnification. Green peach aphid antennae attach to bumps or rounded projections (tubercles) on the front of the head, with a distinct indentation between; the tubercles slightly converge (point towards each other) so the head depression is wider at the base than the opening. Green peach aphids are commonly pale green overall, but can be yellowish, red, rose-pink, or whitish. The antennae and cornicles are relatively long, extending beyond the rear of the body. Winged adults have a black to dark green head and blotch on top of the abdomen and thorax.

    Melon (cotton) aphids have no antennal tubercles; the front of their head is relatively flat, including where antennae attach. Melon aphids are commonly dark to light green, but can also be gray, orangish, yellow, or whitish. Melon aphids populations commonly consist of a mix of colors. Their cornicles are stout and relatively short and entirely black. Antennae when folded over the back reach only to the middle of the abdomen. Winged adults have a black head and thorax.

    Adult (reproducing) aphids may or may not have wings. Winged aphids are produced when plants become heavily infested and the aphids crowded or plant quality declines and when day length shortens during the fall. Green peach aphids produce winged adults at lower population densities than the melon aphid. The optimal temperature for green peach aphid development is 75°F, whereas melon aphid develops fastest above 75°F.

    During most of the year adult aphids give birth to nymphs; eggs hatch within females except when laid for overwintering in the fall. Depending upon temperature, aphids commonly mature and begin giving birth when they are 7 to 10 days old. Under optimal conditions, aphids of many species can complete 1 generation in about 1 week.

    Damage

    Aphids have tubular, sucking mouthparts and excrete copious amounts of sticky, sweet honeydew as they feed. The honeydew can foul plant parts and induce growth of blackish sooty mold fungi. The translucent to white cast skins of aphids stick to surfaces and detract from plants' appearance. Feeding by abundant aphids can cause foliage to yellow. Leaves and shoots infested while immature can become twisted as they grow. Melon aphids transmit (vector) at least 44 plant viruses. Green peach aphids transmit more than 100 plant viruses.

    Management

    Biological control, cultural controls (e.g., excellent sanitation, exclusion, and reflective mulches), and insecticide application are key methods for managing aphids.

    Biological Control

    Important predators of aphids include brown lacewings, green lacewings, lady beetles and the larvae of various flies, including aphid flies, aphid midges, and flower flies or syrphids. Some of these are commercially available for purchase and release, such as the aphid midge Aphidoletes aphidimyza that is commonly released for aphid control in greenhouses and nurseries and has been well-demonstrated to be effective when properly used. The larval stage of parasitic wasps such as Aphelinus abdominalis, Aphidius spp., and Diaeretiella rapae are important natural enemies of many aphid species. Some of these parasites are also commercially available; banker plants may be the most common method of economically sustaining parasitic wasps for aphid control (PDF).

    The most economical and effective method for using biological control in field crops is to conserve naturally occurring parasites and predators. Control ants and dust and rely mostly on types of acaricides (miticides) and insecticides that are not persistent and toxic to natural enemies. These methods are necessary for both naturally occurring and released parasites and predators to be effective. Unless additional, compatible methods are employed for aphids that infest marketed parts of plants, biological control alone generally does not provide satisfactory control. For more information, see Natural Enemy Releases for Biological Control of Crop Pests, Protecting Natural Enemies and Pollinators, and Relative Toxicities of Pesticides Used in Floriculture and Nurseries to Natural Enemies and Honey Bees..

    Cultural Control

    Since common pest aphids feed on a wide variety of plant species. Keep production areas free of weeds that can host aphids. Exclude winged adults by covering greenhouse openings with screens that have a pore width of 0.355 mm (355 microns, about 1/100 inch) or smaller and sufficient surface area to allow adequate ventilation.

    Before starting a new crop, carefully inspect the plants to ensure that they are free of aphids and other pests. Treat effectively or rogue any infested plants. Avoid the use of excess nitrogen fertilizer, which can increase aphid abundance.

    Reflective mulch
    For field-grown crops, applying reflective mulch in the middle of planted rows or entirely covering the soil surface and planting through holes in the mulch can greatly reduce the extent of aphid infestation. Reflective mulch also reduces infection from insect-transmitted viruses when crops are young and most susceptible to damage by these plant pathogens. Reflective mulch can increase crop growth and the yield of cut flowers and reduce the frequency of irrigation by conserving soil moisture. See Reflective Mulches for more information.

    Organically Acceptable Methods

    Biological and cultural controls are organically acceptable aphid management methods. Certain insecticides are acceptable for organic use, including the botanicals azadirachtin, neem oil, and pyrethrins without piperonyl butoxide (PyGanic), the microbial Beauveria bassiana, and certain oils (Organic JMS Stylet Oil).

    Monitoring and Treatment Decisions

    Melon aphids tend to occur throughout infested plants, and their presence on the underside of lower leaves can easily go undetected if these areas are not inspected. Green peach aphids tend to occur mostly around growing points, so their presence is more readily observed. Green peach aphids produce winged individuals at lower densities than melon aphids on crops such as chrysanthemums.

    Yellow sticky cards can be used to detect  winged aphids. Consider treating if there is an average of 5 to 10 aphids per card per week. However, since aphids produce winged individuals in response to crowding, they may be abundant on plants before they are found on sticky traps. Visually inspect plants for aphids, cast skins, honeydew, and sooty mold. For more information, see Monitoring with Sticky Traps and Sticky Trap Monitoring of Insect Pests.

    Selected Products Registered for Greenhouse or Nursery Ornamentals

    Common name Amount to use REI‡ PHI‡
    (Example trade name) (hours) (days)
    Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest integrated pest management (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 product label. Before using a pesticide for the first time or on a new crop or cultivar, treat a few plants and check for phytotoxicity periodically before deciding whether to apply that product more extensively.
    A. POTASSIUM SALTS OF FATTY ACIDS3
      (M-Pede)# Label rates 12 0
      MODE-OF-ACTION GROUP NUMBER1: —
      COMMENTS: Insecticidal soap. Must contact insect, so thorough coverage is important. This insecticide may not effectively control melon aphid because it is often on the underside of lower leaves. Do not make more than three sequential applications. Test for phytotoxicity. Do not spray new transplants or newly rooted cuttings. Do not add adjuvants.
       
    A. NARROW-RANGE OIL3
      (JMS Stylet Oil, Organic JMS Stylet Oil)# 1 oz/gal water 4 0
      MODE-OF-ACTION GROUP NUMBER1: —
      COMMENTS: Works mainly on contact but may also be repellent. Do not spray stressed plants. Target pest must be completely covered with spray. This insecticide may not effectively control melon aphid because it is often on the underside of lower leaves. Check label for plants that can be treated. Do not use with sulfur products; check label for tank mix restrictions.
       
    A. CINNAMALDEHYDE
      (Cinnacure A3005) Label rates 4 0
      MODE-OF-ACTION GROUP NUMBER1: —
      COMMENTS: A botanical-based synthetic. Use product within 10 days of breaking seal. Do not apply to plants that are stressed or recent transplants until roots are well established.
       
    A. NEEM OIL3
      (Triact 70, Trilogy)# 1–2 gal/100 gal water 4 NA
      MODE-OF-ACTION GROUP NUMBER1: UNE
      COMMENTS: A botanical oil with unknown mode of action. Do not spray stressed plants. Target pest must be completely covered with spray. This insecticide may not effectively control melon aphid because it is often on the underside of lower leaves. Check label for plants that can be treated. May injure flowers.
     
    B. BEAUVERIA BASSIANA
      (BotaniGard 22 WP) 0.5–1 lb/100 gal spray volume 4 0
      (BotaniGard ES) 0.5–1 qt/100 gal spray volume 4 0
      (Mycotrol ESO)# 0.5–1 qt/100 gal spray volume 4 0
      MODE-OF-ACTION GROUP NUMBER1: UNF
      COMMENTS: An insect pathogenic fungus. Apply every 7 days if warranted. Do not tank mix with most fungicides; wait 48 hours after application to apply any fungicide.
     
    C. AZADIRACHTIN
      (Azatin O)# 10–16 fl oz/100 gal water 4 0
      (Ornazin 3% EC) Indoor: 8 oz/100 gal
    Outdoor: 10 oz/acre
    12 0
      MODE-OF-ACTION GROUP NUMBER1: UNE
      COMMENTS: A botanical insect growth regulator (IGR). Must contact insect. Repeat applications as necessary. Aphid suppression only. Label permits low-volume application. Do not exceed 22.5 oz/acre per application.
     
    D. S-KINOPRENE
      (Enstar AQ) Label rates 4 NA
      MODE-OF-ACTION GROUP NUMBER1: 7A
      COMMENTS: An insect growth regulator (IGR). Apply pre-bloom. Also labeled for low volume use.
       
    D. PYRIPROXYFEN
      (Distance) 6–8 fl oz/100 gal water 12 NA
      MODE-OF-ACTION GROUP NUMBER1: 7C
      COMMENTS: An insect growth regulator (IGR). Do not apply more than twice per crop or per 6 months. Do not apply through any type of irrigation system.
       
    D. CHLORANTRANILIPROLE
      (Acelepryn) Label rates 4 NA
      MODE-OF-ACTION GROUP NUMBER1: 28
      COMMENTS: A diamide. Do not apply more than 38.3 fl oz per acre per year.
     
    E. PYMETROZINE
      (Endeavor) 2.5–5.0 oz/100 gal water 12 NA
      MODE-OF-ACTION GROUP NUMBER1: 9B
      COMMENTS: A pyridine. Apply as foliar spray at 7 to 14 day intervals. For outdoor use do not apply more than 48 oz/acre per year. For indoor use do not use more than 100 oz.
     
    F. PYRETHRINS
      (PyGanic EC 5.0 II, PyGanic EC 1.4 II)# Label rates 12 0
      MODE-OF-ACTION GROUP NUMBER1: 3A
      COMMENTS: A botanical.
       
    F. PYRETHRINS/PBO2
      (Pyrethrum TR) Label rates 12 NA
      MODE-OF-ACTION GROUP NUMBER1: 3A/—
      COMMENTS: An aerosol botanical and synthetic synergist pre-mix.
     
    G. IMIDACLOPRID4
      (Marathon 1% Granular) Label rates 124 NA
      MODE-OF-ACTION GROUP NUMBER1: 4A
      COMMENTS: A neonicotinoid. Do not apply to soils that are waterlogged or saturated. Do not apply to bedding plants intended to be used as food crops.
     
    H. ACEPHATE
      (Acephate 97UP, Orthene Turf, Tree & Ornamental WSP, 1300 Orthene TR) Label rates 24 NA
      MODE-OF-ACTION GROUP NUMBER1: 1B
      COMMENTS: An organophosphate. 1300 Orthene TR is an aerosol organophosphate only for greenhouse use. Orthene Turf, Tree & Ornamental WSP is only for a limited number of nursery crops; consult label for permitted uses. Phytotoxic to some chrysanthemum varieties. Can stunt new growth in roses. Do not use through any type of irrigation system.
     
      Pyrethroids (below) are generally ineffective for green peach aphid because of resistance. Apply them only if melon aphid or other aphid species are the problem.
    I. BIFENTHRIN5
      (Talstar S Select) 5–10 fl oz/100 gal water 12 NA
      MODE-OF-ACTION GROUP NUMBER1: 3A
      COMMENTS: A pyrethroid.
       
    I. CYFLUTHRIN5
      (Decathlon 20 WP) 1.9 oz/100 gal water 12 NA
      MODE-OF-ACTION GROUP NUMBER1: 3A
      COMMENTS: A pyrethroid.
       
    I. FENPROPATHRIN5
      (Tame 2.4 EC) ¬†Label rates 24 NA
      MODE-OF-ACTION GROUP NUMBER1: 3A
      COMMENTS: A pyrethroid.
       
    I. LAMBDA-CYHALOTHRIN5
      (Scimitar GC) 1.5–5 fl oz/100 gal water 24 NA
      MODE-OF-ACTION GROUP NUMBER1: 3A
      COMMENTS: A pyrethroid. Apply at 7-day intervals if warranted. Do not apply more than 52.4 fl oz of concentrate/acre per year. Do not mix with EC formulations or oils.
       
    I. PERMETHRIN5
      (Perm-UP 25 DF) Label rates 12 NA
      MODE-OF-ACTION GROUP NUMBER1: 3A
      COMMENTS: A pyrethroid. Direct application to blooms may cause browning of petals. Marginal leaf burn may occur on dieffenbachia, pteris fern, and salvia. Label permits low-volume application.
       
    I. TAU-FLUVALINATE5
      (Mavrik Aquaflow) 4–10 fl oz/100 gal water 12 NA
      MODE-OF-ACTION GROUP NUMBER1: 3A
      COMMENTS: A pyrethroid. Label permits low-volume application. Also labeled as a cutting dip at 5 fl oz/100 gal. Greenhouse, interiorscape, outdoor ornamental plantings, plantscapes, and containerized nursery stock only.
    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.
    # Acceptable for use on organically grown ornamentals.
    Unknown.
    NA Not applicable.
    1 Rotate pesticides with a different mode-of-action group number, and do not use products with the same mode of action more than twice per season to help prevent the development of resistance. For example, 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 for acaricides (miticides), insecticides, nematicides, and molluscicides are assigned by the Insecticide Resistance Action Committee (IRAC).
    2 PBO = piperonyl butoxide.
    3 Single doses of oils and potassium salts of fatty acids (soaps) can be used anytime as pesticide rotation without negatively impacting resistance management.
    4 If the product is drenched, soil injected, or soil incorporated workers may enter the treated area at anytime if there will be no contact with anything that has been treated.
    5 Pyrethroids generally are not effective against green peach aphid because excess exposure to them has induced development of resistance. Apply them only when melon aphid or other aphid species are the problem.
    Text Updated: 01/22
    Treatment Table Updated: 01/22
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