Description of the Pest
Aphids are distinguished from other insects by the presence of cornicles, tubelike appendages that protrude from the rear of the aphid. Numerous species of aphids attack California ornamental crops, but the two species most commonly encountered are the green peach aphid and the cotton or melon aphid. Melon aphids are typically dark green, but color variations do occur frequently. The cornicles are relatively short, stout, and always dark. Melon aphids have red eyes and antennae that only reach to the middle of the abdomen. Green peach aphid is characterized by a depression in the front of the head between the antennae (best seen with the use of a hand lens) and by long thin, translucent cornicles that extend beyond the tip of the body. Green peach aphids vary in color from yellowish green to rose pink. Winged adults have a dark blotch in the middle of the abdomen.
Adult aphids may or may not have wings. Winged aphids are produced as a result of crowding. 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 optimal temperatures for development of melon aphids are above 75°F.
Adult aphids give birth to live young. Generally, aphids begin giving birth when they are 7 to 10 days old, depending on temperature.
Aphids excrete copious amounts of honeydew, a sweet, sticky substance that they produce as they feed on the plants. The honeydew can cover leaves and other plant parts and cause the plants to become sticky. Black sooty molds then grow on the honeydew. The white shed skins of the aphids frequently are stuck to the plant surfaces by the honeydew and further detract from the plant's appearance. Sufficient feeding can cause foliage to become yellowed, and feeding on newly developing tissues can cause those parts to become twisted as they grow. Melon aphids are known to transmit 44 plant viruses, while green peach aphids are known to transmit more than 100 plant viruses.
Predators such as lacewings (Chrysoperla spp.) and midges (Aphidoletes aphidimyza) are commercially available. Parasites, such as Aphidius spp., Lysiphlebus testaceipes, Diaeretiella rapae, and Aphelinus abdominalis, are also commercially available. For more information, see BIOLOGICAL CONTROL.
Because aphids feed on a large variety of plant species, keep production areas free of weeds, which can serve as hosts of aphid populations. Exclusion of winged adults can be accomplished by covering openings to the greenhouse with screens that have a pore width of 355 microns or smaller. Before starting a new crop, carefully inspect plants to ensure that they are free of aphids and other pests. Treat or rogue any infested plants.
Monitoring and Treatment Decisions
Yellow sticky cards placed in greenhouses will capture winged adults. However, aphids produce winged individuals in response to crowding so monitoring plants for infestations is an essential component of managing and detecting these pests before populations get too high. Melon aphids tend to have a more uniform vertical distribution on plants than green peach aphids, which tends to be clustered around growing points, meaning that infestations of melon aphids under lower leaves can easily go undetected if these areas are not inspected. Green peach aphids will produce winged individuals at lower densities than melon aphids on crops such as chrysanthemums. Use at least one sticky trap per 10,000 square feet (900 sq m) of growing area for monitoring aphids. For more information, see MONITORING WITH STICKY TRAPS.
Consider treating if an average of 5 to 10 aphids per card per week is present.
Selected Materials Registered for Use on Greenhouse or Nursery
Read and follow the instructions on the label before using any pesticide. Before using a pesticide for the first time or on a new crop or cultivar, treat a few plants and check for phytotoxicity. Also consider pesticide resistance management and environmental impact.
|Manufacturer||REI1||Mode of action2||Comments|
(BotaniGard 22 WP)
|Treat every 7 days while insects are active. Do not tank mix with most fungicides and wait 48 hours after application to apply a fungicide.|
|Proguard||4||—||Do not apply to stressed plants or newly transplanted material before roots are established.|
(PT Pyrethrum TR)
|Whitmire MicroGen||12||3||An aerosol.|
|Gowan||24||1A||Apply in 50 gal water. Repeat as necessary up to 2 applications/season. Do not apply with oil or foliar fertilizer.|
|insect growth regulator||A.||azadirachtin
|OHP||4||un||Must contact insect. Repeated applications as necessary. Aphid suppression only. Label permits low-volume application.|
|SePRO||12||un||Do not exceed 22.5 oz/acre/application.|
|Valent||12||7C||Do not apply more than 2 times per cropping cycle or per 6 months.|
|Wellmark||4||—||Apply prebloom. Also labeled for low volume use.|
||12||4A||Not to be used more than once every 16 weeks. Do not apply to soils that are water logged or saturated. Do not apply to bedding plants intended to be used as food crops.|
(Marathon 60 WP)
|OHP||12||4A||As above, but apply only as a drench.|
hydrophobic extract of neem oil#
|OHP||4||un||Do not spray plants under stress. Target pest must be completely covered with spray—this material may not effectively control melon aphid because it is often on the underside of lower leaves. Check label for list of plants that can be treated. May cause injury to flowers.|
(JMS Stylet Oil)
|Use as above for neem oil. Also, do not use with sulfur fungicides; check label for tank mix restrictions.|
(Orthene T, T&O Spray)
|Valent||24||1B||A number of chrysanthemum varieties have exhibited phytotoxic reactions. Only labeled for use on anthurium, cacti, carnation, rose, orchids, some foliage plants, young poinsettia and some varieties of chrysanthemum. Can stunt new growth in roses.|
(PT 1300 Orthene TR)
|Whitmire MicroGen||24||1B||An aerosol that is only for greenhouse use.|
|Whitmire MicroGen||12||3||Check label. A fogger for greenhouse use only.|
|FMC||12||3||Label permits low-volume application.|
(Decathlon 20 WP)
|OHP||12||3||Label permits low-volume application.|
(Tame 2.4 EC)
|Valent||24||3||Label permits low-volume application.|
|Wellmark||12||3||Label permits low-volume application. Also labeled as a cutting dip at 5 fl oz/100 gal.|
|Syngenta||24||3||For greenhouse and nursery use. Apply at 7-day intervals. Do not apply more than 52.4 fl oz of concentrate/acre/year. Do not mix with EC formulations or oils.|
|FMC||12||3||Direct application to blooms may cause browning of petals. Marginal leaf burn may occur on salvia, diffenbachia and pteris fern. Label permits low-volume application. Do not apply more than 2 lb a.i./acre/year.|
|pyridine||A.||pymetrozine (Endeavor)||Syngenta||12||9B||Apply as foliar spray at 7-14 day intervals. For outdoor use, do not apply more than 48 oz/acre/year; for indoor use, do not use more than 100 oz.|
|soap4||A.||potash soap# (M-Pede)||Dow Agro
|12||—||Must contact insect, so thorough coverage is important. Repeat weekly as needed up to 3 times. Test for phytotoxicity. Do not spray new transplants or newly rooted cuttings. Do not add adjuvants.|
|1||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.|
|2||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).|
|3||PBO = piperonyl butoxide|
|4||Note that single doses of soaps or oils can be used at anytime in a pesticide rotation scheme without negatively impacting resistance management programs.|
|5||Check with certifier to determine which products are organically acceptable.|
|6||Pyrethroids are generally not effective against green peach aphid.|
|*||Restricted use material. Permit required for purchase or use.|
|#||Acceptable for use on organically grown ornamentals.|