Agriculture: Floriculture and Ornamental Nurseries Pest Management Guidelines


  • American serpentine leafminer: Liriomyza trifolii
  • Leafminers: Phytomyza spp. and others
  • Pea leafminer: Liriomyza huidobrensis
  • Vegetable leafminer: Liriomyza sativae
  • Description of the Pest

    Adult Liriomyza spp. are about 1/12 inch long and mostly black and yellow flies with clear wings. Phytomyza spp. adults are mostly blackish or gray on top with a white to yellowish abdomen. Females of both genera insert tiny eggs in leaves of numerous crop and weed hosts where the larvae feed within leaf tissue. Adult females also puncture leaf surfaces to feed on the oozing plant juices.

    There are many types of leafmining insects in addition to Liriomyza and Phytomyza spp. flies (Agromyzidae). Leafminer pests of azalea and rhododendron include Caloptilia azaleella, a brown, gray, and silvery moth (Gracillariidae) with larvae up to 1/2 inch long. Chrysanthemum leafminers include Chromatomyia syngenesiae, Liriomyza spp., and Phytomyza atricornis, all agromyzid flies. Columbine leafminers include Phytomyza spp.; adults are commonly grayish. Manzanita and madrone are hosts to Marmara arbutiella (Gracillariidae), small brown and whitish moths with yellowish larvae with distinct, triangular-shaped segments. Orchids and cymbidium are attacked by larvae of a moth, Pyroderces badia (Cosmopterigidae). If it is uncertain what species of leafminer are the problem several can be collected, such as with an aspirator, and taken to the local office of the county department of agriculture or University of California Cooperative Extension for identification.

    Larvae of Liriomyza and Phytomyza spp. are orangish or yellow and develop through three increasingly larger instars. Larvae widen and lengthen their mine as they grow up to about 1/10 inch long. Liriomyza trifolii mines are readily observed from the top of the leaf, while Liriomyza huidobrensis mines may only be apparent from the underside of the leaf. Liriomyza huidobrensis mines tend to follow the veins of the leaf.

    At maturity, leafminer larvae commonly exit mines and pupate in growing media or topsoil. Liriomyza pupae are orange or yellow and those of Phytomyza are gray. Uncommonly pupae are observed on leaves. Liriomyza leafminers have multiple generations per year. For example, Liriomyza trifolii can complete 1 generation in about 1 month at common greenhouse temperatures, or in 14 days or 64 days at 95° and 59°F, respectively.


    Adults' feeding punctures in leaves turn white, resulting in numerous round pale blotches in foliage. The most obvious damage is from the larval mines that make foliage unsightly and when abundant render plants unmarketable. Although high populations of leafminers rarely if ever kill hosts, mining may slow crop growth and cause infested leaves to drop prematurely.


    Biological and cultural controls and insecticide applications are used to manage leafminers.

    Biological Control

    Parasitic wasps generally keep leafminer populations low in field-grown plants unless biological control is disrupted. Outbreaks of leafminers commonly occur when broad-spectrum, persistent, insecticides applied for other pests kill leafminers' natural enemies. To conserve natural enemies, control ants, reduce dustiness, and where feasible rely on cultural controls and selective and semi-selective insecticides for all pests as listed in Relative Toxicities of Pesticides Used in Floriculture and Nurseries to Natural Enemies and Honey Bees.

    The Liriomyza larval parasites Dacnusa sibirica and Diglyphus spp. are commercially available and effective for controlling leafminers in greenhouses and shade structures that are adequately screened to contain the parasites and exclude in-migrating adult leafminers and other pests. For more information, see Biological Control, Protecting Natural Enemies and Pollinators, and Natural Enemy Releases for Biological Control of Crop Pests.

    Cultural Control

    Carefully inspect plants to ensure they are pest free before moving them to production areas; discard infested plants or leaves or effectively treat plants. Steam treat planting beds or otherwise pasteurize growing media to the recommended pasteurization temperature immediately after removing any infested crop to kill any leafminer pupae in the soil before replanting beds. Steam is difficult to use in field soils but can be applied using a plowlike steam rake to raise the topsoil temperature to levels sufficient to kill most pests.

    Keep growing areas and sites bordering crops free of weeds, which can host leafminers; Liriomyza and Phytomyza spp. leafminers feed on a wide variety of plant species and readily move among hosts. Promptly dispose of plant debris in covered containers. Exclude migrating adults by properly screening doors, vents, and other openings to greenhouses and screenhouses. Effective screens have an opening width of 600 microns (0.6 mm, or about 1/40 inch) or smaller and sufficient surface area to provide adequate ventilation.

    Organically Acceptable Methods

    Biological and cultural controls are organically acceptable management methods. Certain formulations of the botanical azadirachtin (Azatin) and the fermentation product spinosad (Entrust Naturalyte, Entrust SC) are organically acceptable.

    Monitoring and Treatment Decisions

    Deploy yellow sticky traps in greenhouses to attract and capture adults. Place at least 1 trap per 10,000 sq. ft. of growing area. Monitor traps weekly; count and record the results. Change traps when they are fouled or have trapped too many insects to readily count. For side-by-side comparisons to help identify the captured insects, see Sticky Trap Monitoring of Insect Pests. For more information, see Monitoring with Sticky Traps and Establishing Action Thresholds.

    Insecticide resistance is widespread in populations of Liriomyza; some products listed below may not be effective depending on the exposure history and pesticide tolerance of local leafminer populations. Rotate between effective products with a different mode of action every 1 to 2 months if ongoing applications are targeting leafminers. See Managing Pesticide Resistance for more information.

    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.
    (Ornazin 3% EC) Indoor: 10 oz/100 gal
    Outdoor: 10 oz/acre
    12 0
    COMMENTS: A botanical and insect growth regulator (IGR). Do not exceed 22.5 oz/acre per application.
    (Mainspring GNL) 2–8 fl oz/100 gal water 4 NA
    COMMENTS: A ryanodine receptor modulator. Apply as a spray or drench.
    (Citation) 2.66 oz/acre 12 NA
    COMMENTS: An insect growth regulator (IGR). Also effective against fungus gnat larvae. Labeled for low volume applications.
    (Pedestal) 6–8 fl oz/100 gal water 12 NA
    (Abamectin 0.15EC, Avid 0.15EC) Label rates 12 NA
    COMMENTS: An avermectin. Add narrow-range oil to the mix to improve efficacy persistence if allowed by both labels; if so do not spray stressed plants and do not use with sulfur products. Apply as a spray. Label permits low-volume application. Do not apply through certain types of irrigation systems; consult label for restrictions.
    (Conserve SC) 22 fl oz/100 gal water 4 NA
    (Entrust)# 3.1 oz/100 gal water 4 NA
    COMMENTS: A microbial-derived insecticide. Adding narrow-range oil to the spray mix and using water with a pH of 6 to 8 can increase the translaminar (into leaf) movement and persistence.
    (Azatin O)# 6–16 fl oz/100 gal water 4 0
    COMMENTS: A botanical and insect growth regulator (IGR). Must contact insect. Repeat applications as necessary. Label permits low-volume application.
    (Orthene Turf, Tree & Ornamental WSP, 1300 Orthene TR) Label rates 24 NA
    COMMENTS: An organophosphate. 1300 Orthene TR is an aerosol only for greenhouse use. Orthene Turf, Tree & Ornamental WSP is labeled 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.
    (Perm-UP 25 DF) 6.4–12.8 fl oz/100 gal water 12 NA
    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. Do not apply more than 2 lb a.i./acre per year.
    (TriStar 8.5 SL) 21.0–25.3 oz/100 gal water 12 NA
    COMMENTS: A neonicotinoid. Apply as a foliar spray. Label permits low-volume application. Do not apply through certain types of irrigation systems; consult label for restrictions.
    (Safari 20G) Label rate 12 NA
    COMMENTS: A neonicotinoid. Can be applied as a drench or foliar spray.
    (Marathon 1% Granular) Label rates 122 NA
    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.
    (Flagship 25WG) Label rates 12 NA
    COMMENTS: A neonicotinoid. Can be applied as a drench or foliar spray.
    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.
    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 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.
    Text Updated: 01/22
    Treatment Table Updated: 01/22