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Greenhouse Peppers

Greenhouse Peppers:
Guidelines for Biological Control

Printable tech sheet (PDF)

Biological controls have been used in greenhouse peppers since the crop began to be grown in BC in the mid-1980’s. Biological control is most effective when used in an Integrated Pest Management (IPM) program (see Integrated Pest Management ). As in any IPM program, success depends upon correct identification of pest problems, regular monitoring, careful timing and integration of complementary control measures. It also depends on good clean-up, sanitation and other measures that remove breeding sites for pests and prevent them from entering the greenhouse.

The primary pests in greenhouse peppers are fungus gnats (Bradysia spp.), western flower thrips (Frankliniella occidentalis), two-spotted mites (Tetranychus urticae), green peach aphid (Myzus persicae) and greenhouse whitefly (Trialeurodes vaporariorum). Lygus bugs, cabbage loopers, and other species of aphids also occur.

Pepper plants have three characteristics that enhance the use of biological controls:
The presence of pollen and nectar in the flowers. This provides an alternative food
  source for some biological controls (i.e. predatory bugs and mites, such as ‘Orius’
  and ‘Cucumeris’ making them easier to establish.
Smooth leaves. This means that predators are able to travel freely over the leaves
   and between plants, without being hindered by hairs as they are on cucumber and
   tomato leaves.        
Limited leaf pruning is necessary. This retains leaves of all ages, allowing all stages of
   biological controls to reproduce and complete their life cycles without disturbance.     

The following guidelines contain practical tips for achieving good results using biological controls against pests in greenhouse peppers. Recommended release rates for each biological control are shown in Table 1. More detailed information on pests and biological controls can be found in the separate information sheets for each species.

  • IPM for peppers begins with seedling production. It is important that propagators establish the fungus gnat predator, Stratiolaelaps (formerly called Hypoaspis miles) at the seedling stage. Other biological controls should also be used early if pests, such as thrips, spider mites or aphids occur, rather than applying pesticides. Propagators must supply information about all pesticides that have been used on seedlings. This is critical information as most pesticides interfere with, and can seriously limit, later use of biological controls. This is especially true of residual pesticides. (For more information of the effects of pesticides on biological controls, contact Sound Horticulture.

  • There are two main ways to monitor for common pepper pests:
    • Trapping pests on sticky cards or ribbons. Yellow traps are used to monitor for
       fungus gnat, thrips, whitefly and Lygus bugs. Blue traps are also used for thrips, but
       yellow traps are usually preferred because they can be used for other insects as
       well.Inspect traps weekly; replace every 3-4 weeks as glue becomes less effective.
       Place traps at the top of the plant canopy for whiteflies and thrips; place them about
       1 ft. (25 cm) above the growing media for fungus gnats      
    •Visual inspection of plant leaves. This should be done weekly for signs of two-spotted
      mites, aphid infestations, cabbage looper damage, Lygus nymphs and other
      problems. At the same time, record the presecnce or absence of biological controls
      in infested areas.

  • Fungus gnats can cause significant damage in soil-less or sawdust bag cultures. In peppers, most damage is caused by the larvae feeding on tender roots. As root area is lost, pepper plants become more susceptible to drought stress and root rot infections. Adult fungus gnats can also transmit root rot and other diseases. (For more information, see Fungus Gnats.)
    Monitoring Tips
    • Use yellow sticky cards at a rate of 1 trap/5,000 ft(500 m2).
    • Place cards about 25 cm (1 ft) above the soil or rockwool surface.
    • Check traps weekly and record the number of adult fungus gnats; replace traps
       every 3-4 weeks as the glue dries out.

    It is important to distinguish between fungus gnats and shore flies because biological controls for fungus gnats do not work on shore flies (for descriptions, see Fungus Gnats).

    Release Biological Controls The following three species of biological controls are compatible with each other and can be used together.

    Stratiolaelaps(formerly called Hypoaspis miles): This soil-dwelling predatory mite feeds on fungus gnat larvae. The best way to use Stratiolaelaps is to establish it in the greenhouse before fungus gnats appear. Apply to pepper seedlings in flats or cubes at the start of the growing season, and then again when planting out. By feeding on other soil organisms, Stratiolaelaps populations can build up to high numbers that are effective in keep fungus gnat populations low.(For more information, see Stratiolaelaps).

    Supplement Stratiolaelaps with other biocontrols (below) if fungus gnat populations are high.

    Insect Parasitic Nematodes: Steinernema carpocapsae, S. feltiae, and Heterorhabditis spp. are beneficial nematodes sold to control fungus gnats and other insects (see Misc. Biological Controls). They can be applied to the soil through conventional sprayers or through the irrigation system. Nematodes are effective against high populations of fungus gnats but, unlike Stratiolaelaps, will not reproduce or remain in the growing media and must be reapplied.

    Apply nematodes or BTI (see below) when yellow sticky traps average over 20 fungus
    gnat adults per trap, weekly, or while fungus gnat populations appear to be increasing.
    • If  root diseases are a problem in the crop, apply nematodes sooner to reduce the risk
      of disease transmission by fungus gnat larvae.
    • Three applications, 7-10 days apart, are usually required. Nematode products vary,
      so always follow product recommendations for rates. Calculate application on the
      actual growing area, not greenhouse area.

    Note: The actual growing area for rockwool cultures with plant densities of 1.2-1.4 plants/10 ft2 (m2) is typically 1/3 to 1/4 of the total floor space.

    Bacillus thuringiensis israelensis (BTI): A strain of this bacteria that infects fungus gnat larvae is available (Vectobac®). It is applied in water to the soil or growing media after fungus gnats are established (follow instructions on the product label).

    Other Measures
    • It is essential to eliminate wet spots in the greenhouse where fungus gnats can breed
      by improving drainage, repairing leaks in plumbing, adjusting automatic irrigation
      equipment, etc.    
    • Control is usually better in greenhouses with white plastic floors because fewer
      breeding sites are available for fungus gnats.
    • Control fungus gnats in other crops in adjacent greenhouses.

  • Western flower thrips (WFT) damage leaves and distort the fruit of peppers by feeding and laying eggs in leaf and flower tissues and young developing fruit. When western flower thrips populations are high the adults may be found in high numbers in the pepper flowers. Onion thrips will also attack peppers but the damage is usually confined to the older leaves and is less severe (for more information, see Thrips).

    Monitoring Tips
    • Use yellow or blue sticky cards (using the same yellow cards for whitefly monitoring
      saves time) at a rate of 1 trap/500-1000 ft2 (50-100 m2). Place traps at the top of plant
    • Count the number of thrips on traps weekly; replace traps every 3-4 weeks as the
      glue dries out.  
    • Examine a minimum of 20 leaves from mid-plant level in each infested area. Look
      for presence or absence of both thrips and Cucumeris predatory mites. When each
      leaf with thrips also has predators present, it is an indicator that the thrips population
      should begin to decline.
    • When an average of 1 Orius/week are being caught on traps, it is an indication that
      Orius numbers have increased and adult thrips numbers should decline.

    Release Biological Controls
    The following three species of biological controls are compatible and can be used together.

    Stratiolaelaps(formerly called Hypoaspis miles): This soil-dwelling mite feeds on the immature stages of thrips in the soil or growing media. Stratiolaelaps alone cannot control thrips infestations, but it contributes to the effectiveness of biological control when used with other predators. (For more information, see Stratiolaelaps.)

    Cucumeris’: The predatory mite Amblyseius cucumeris feeds on immature stages of thrips as well as pepper pollen. Once pollen is present, Cucumeris can usually be established on peppers. Cucumeris is available in a loose bran carrier, which is sprinkled onto leaves or on young plants without pollen. Small piles of carrier containing Cucumeris can also be placed next to plant stems. Releases should start assoon as the first flowers are set and continue until there is a 1:1 ratio of thrips to Cucumeris on leaves, as determined by monitoring (see above). For more information see Cucumeris).

    It usually takes 4-6 weeks before changes in thrips numbers caught on traps will be noticeable as a result of releasing Cucumeris.

    Avoid using Cucumeris on pepper plants where spider mites are also a problem. This is because Cucumeris, which also feeds on spider mite eggs, can increase to such high populations on peppers that they reduce the amount of food available for spider mite predators such as Persimilis. To control thrips where spider mites are also a problem, it is better to use the predatory mite, ‘Degenerans’ (see below).

    Degenerans’: Another predatory mite, Amblyseius degenerans, can be used on peppers to control thrips. Release as soon as plants are flowering and pollen is present. Degenerans are best released in clumps at the end and middle of rows as females require repeated mating for egg laying. When pollen is present for this predator will rapidly increase and spread throughout the greenhouse. (For more information see Degenerans under Misc. Biological Controls.) Note: Degenerans is more susceptible to pesticides than Cucumeris.  Contact Sound Horticulture for specifics.

    Orius’: The tiny pirate bug (Orius spp.) feeds on all stages of thrips, but it is used in peppers mainly to control the adult thrips that congregate and feed in flowers. Orius is only effective from March to September because they do not reproduce if day length is less than 16 hours. Orius should be released in March, or as soon as thrips are detected, where thrips numbers are the highest in the greenhouse. Release at least 500 Orius at one time to establish a breeding population. (For more information see Orius.)

    Other Measures
    • Avoid thrips re-infestations by thoroughly cleaning up the crop at the end of the
      season. Treat the greenhouse with naled (Dibrom®) after the last pick, before
      removing pepper plants, and again after the greenhouse is empty.
    •To starve thrips between crops, maintain a heated greenhouse, empty of plants,
      which forces adult thrips to emerge from the soil-borne pupal stages.
    • If thrips populations were high in the preceding crop, it may be advisable to apply
      lime to the ground before covering the greenhouse floor with plastic. Care should be
      taken to overlap and tape, or glue, the floor covering together.
    • Do not maintain any ornamental plants in the greenhouse, and maintain a weed-free
      border, 10 ft (3 m) wide, around the outside perimeter of the greenhouse.

  • TWO-SPOTTED MITES (TSM) Two-spotted mites are common pests of greenhouse peppers. (For more information, see Two-spotted Mites.) During warm weather, TSM populations reproduce very quickly.

    Monitoring Tips
    • Inspect mite damaged leaves under 10-15 X magnification for TSM infestation.
    • Some growers use bean seedlings or climbing runner beans as trap plants to detect
      the first appearance of TSM on new crops. TSM damage is easy to see on bean
      leaves, which alerts growers that there may be mites on pepper plants. Persimilis are
      also easily to establish on the bean plants, which act as nursery or banker plants for
      producing more predators.   

    Release Biological Controls
    Persimilis’: The predatory mite, Phytoseiulus persimilis, is a very effective control for TSM in peppers because the predators develop twice as fast as the pest at moderate greenhouse temperatures. (For more information see Persimilis.)
    • When TSM are first seen, introduce Persimilis onto all infested leaves; continue
      weekly releases until they are present on all TSM infested plants.  
    • Use the Persimilis shipped on bean leaves, rather than vermiculite, because the
      predators survive shipping in better condition and are easier to apply. Place bean
      leaves with Persimilis on pepper leaves near TSM infestations. Alternatively, apply
      the concentrated ‘HOT SPOT’ Persimilis product (which contains high numbers of
      Persimilis in vermiculite) to each infested site.    
    • Once Persimilis are established, speed distribution of the predators by picking
      Persimilis “nursery” leaves and moving them to other plants all around the infested
      sites and throughout the crop.  
    • If TSM populations are high spray once or twice with fenbutatin oxide (Vendex®),
      then release Persimilis when the last spray has dried. Vendex does not kill the egg
      stage of the spider mites and will not harm predatory mites. 
    Once spider mites are eliminated, Persimilis will die out. Therefore, other mite predators that can survive on pollen, such as Fallacis or ‘Californicus’ (see under Misc. Biological Controls)  should be introduced as well. These predators provide some control of TSM, but will not usually control TSM “hot spots”; Persimilis should be reintroduced if these develop.

    Stethorus’: The predatory lady beetle, Stethorus punctillum, feeds on all stages of TSM and can be used with other biocontrol agents. Stethorus is active over a wide temperature and humidity range (61°-86°F/16-30°C and 20-90%RH). They should be released in mite infested sites as soon as TSM are detected. (For more information, see Stethorus.)

    Feltiella’: The larvae of the predatory midge, Feltiella acarasuga, feed on spider mites. They are effective at controlling spider mites early in the season or at times when humidities are high. (For more information, see Misc. Biological Controls.)

    Other Measures
    • Chemical control in conjunction with biological control is recommended if mites are
       clustering in balls or “stringing” down from the plant or detected in high numbers
       without predators present. Fenbutatin oxide (Vendex®) is safe for use with
       predatory mites such as Persimilis and Fallacis, but check compatibility before using
       other pesticides with biological controls. (Contact Sound Horticulture for information.)    
    • Once Persimilis has been released, maintain warm temperatures (optimum
       77°F/25°C) and high humidity (optimum 80-90% RH) to encourage the predatory
       mites. Mist the crop if necessary.
    •  It is important to finish each crop with low populations of TSM. High numbers at the
       end of the year result in the survival of many diapausing (overwintering stage)
       spider mites that will re-infest the next crop early in the season. If mites are still a
       problem in late July, a miticide should be applied in August to prevent diapausing
       mites from over wintering. Pesticides are less effective against the diapausing form
       of TSM. Check compatibility before using other pesticides with biological controls.
       (Contact Sound Horticulture for information.)    

    If large numbers of overwintered TSM occur, or are anticipated in a new crop, a "pest in first" approach should be used. This means introducing TSM along with Persimilis to ensure even establishment and build-up of Persimilis populations.

    Aphids (especially green peach aphid, Myzus persicae) can be a serious problem in greenhouse peppers (for more information see Aphids). In peppers new infestations are usually detected first on the oldest (lowest) leaves and on the young shoots of plants. Aphids reproduce quickly on peppers and all three biological control agents listed below are best used together for long term control.
    • Release ‘Aphidius’ parasitic wasp (Aphidius matricariae) (see Aphidius), at low rates
      as soon as the crop is in the greenhouse.
    • Release ‘Aphidoletes’ aphid midges (Aphidoletes aphidimyza) (see Aphidius) between
      March 15 and August 15, weekly, until aphids are controlled. For heavy infestations
      release a minimum of 2000 aphid midges, weekly, in each aphid “hot spot”.  
    • Release the lady beetle, Harmonia axyridis, to control all species of aphids. If the
      aphid infestation is widespread, also release field-collected Hippodamia convergens as
      well. (For more on both lady beetles, see Lady Beetles.)

    Whiteflies damage greenhouse peppers by covering fruit and leaves with the sticky honeydew as they feed (for more information see Whiteflies) and reducing the vigour of plants. Whiteflies can be controlled by the parasitic wasp, ‘Encarsia’, and the predatory beetle, ‘Delphastus’, by following steps described below.

    Monitoring Tips
    • Begin in the empty greenhouse, before seedlings are planted out.
    • Hang up yellow sticky cards or tapes at the rate of 1 trap/500-1000 ft2  (50-100 m2).
    • Check traps weekly for adult whiteflies.

    Release Biological Controls
    Encarsia’: Encarsia formosa is a tiny, 1/20 inch (1 mm) long, wasp that parasitizes immature stages of whitefly. It is sold as parasitized scales glued to cards, from which the adult wasps emerge. As the wasp develops inside, greenhouse whitefly scales gradually turn black. If there is a history of whitefly problems best results are achieved when Encarsia are introduced preventively, at low rates, before whiteflies are found on monitoring traps. Releases continue, usually weekly and are maintained until 80% of whitefly pupae appear parasitized. (For more information, see Encarsia.) In warm regions or areas where a large number of greenhouses have whitefly infestations, the whiteflies may move onto outdoor plants. This makes them more difficult to control as whiteflies continually re-infest the crop plants. Encarsia are less effective during cool weather and overcast periods, therefore whitefly populations must be monitored closely.


    Dicyphus’: The predatory bug, Dicyphus hesperus is an effective whitefly predator but should not be used on its own to replace other biological control agents. It is best used along with other biological control agents in crops that have, or (because of past history) are expected to have. whitefly, spider mite, or thrips problems.
    • Eggs are laid inside plant tissue and are not easily seen.
    • Adults are slender (6mm), black and green with red eyes and can fly
    • Nymphs are green with red eyes
    • Release Dicyphus as soon as whiteflies are found, early in the season at a rate of
      0.25-0.5 bugs/10 ft2 (m2) of infested area; repeat in 2-3 weeks.  
    Release batches of 100 adults together in one area where whitefly is present.

    Delphastus’: Delphastus catalinae is a small, black, 1.4 mm (1/15 inch) long, lady beetle. Both adults and larvae feed on whitefly eggs and immature stages. Delphastus is sold as adults and should be applied as soon as whitefly are detected. Delphastus works well with Encarsia because it avoids feeding on parasitized whitefly scale. (For more information see Delphastus.)

    Other Measures
    • It is essential to start with a clean crop at the beginning of the season, therefore
      destroy all crop residues and dispose of them at a site remote from the greenhouse.
    • If the previous crop was infested with whiteflies, leave the greenhouse entirely
      empty of plants for 5 days, with heat, to starve whiteflies or kill them with cold by
      allowing the greenhouse to freeze for a week. 
    • If a plant-free period is not possiblebetween crops, use a short-residual fumigant such
      as naled (Dibrom©). Apply at the end of the crop, before removing plant debris, and
      again to the empty greenhouse.   
    • Keep the greenhouse weed-free, and maintain a 10ft (3m) wide, weed-free border
      around the greenhouse.
    • Do not keep ornamental plants in a pepper greenhouse as these are also whitefly
    • If greenhouse whitefly numbers are high, hang yellow sticky tapes (up to 1 tape per
      plant) at the top of the plant canopy to trap adult whiteflies.  
    • If whiteflies are present on outdoor plants, screen all entry points.

    Several species of Lygus bugs attack pepper plants. Their toxic feeding causes abortion or death of the affected growing point.
    • Hand pick and destroy any adults or larvae found on the plants.
    • If intake fans are used, screen with 1/4 inch (5 mm) mesh screen.
    • Release Orius (if not already being used for thrips control), which feed on Lygus
    • Regularly mow the areas around the greenhouse quite short to avoid harboring
    • Light traps will also trap Lygus.

    The caterpillars of several species of moths and butterflies may become serious pests in peppers if their numbers are allowed to build up.
    • Hand pick and destroy any larvae found on young plants; use an ultraviolet (UV)
      light trap to catch adult moths
    • If intake fans are used, screen with 5 mm (1/4 inch) mesh screen. This will also stop Lygus and other flying pests.

     Release Biological Controls
    Trichogramma spp. parasitic wasps (see Trichogramma) attack moth eggs and can
       assist in control.
    • Predatory bugs, such as ‘Podisus’ (see Podisus under Misc. Biological Controls) and Orius
      attack eggs and small stages of caterpillar larvae.  
    • The parasitic wasp ‘Cotesia’ (see under Misc. Biological Controls) attacks caterpillars and may
       be available for release.

  • Summary of IPM Guidelines Greenhouse Peppers
    Between crops:
    • Remove crop debris, heat empty greenhouse for 3-5 days.
    • Cover floors with white plastic.
    • Improve drainage to eliminate wet spots.
    • Remove all weeds inside and around greenhouse perimeter.
    • Screen vents where Lygus bugs are problems.
    At start of crop:
    • Whitefly: Release Encarsia at low rates.
    • Fungus gnats and thrips: Introduce Stratiolaelaps at the start of the crop.
    When pests are detected:
    • Fungus gnats: Apply insect parasitic nematodes, BTI.
    • Whitefly: Release Encarsia until 80% of whitefly pupae are parasitized; release
      Delphastus and Dicyphus.  
    • Two-spotted mites: Apply Persimilis as needed.
    • Western flower thrips: Apply Cucumeris as needed; add Orius if thrips numbers high.
    • Aphids: Release Aphidius, Aphidoletes and, if aphids numbers are high, Harmonia
      and Hippodamia lady beetles.
    • Loopers/Caterpillars: Spray BTK, release Trichogramma, use UV light traps for adults.
    • Lygus: Hand-pick all stages, release Orius.

Table 1


Summary Release Rate Table: Greenhouse Peppers (Planting density 3.3 – 3.5 plants/10ft2 (m2).

Please Note! These rates are only average rates and this may vary with time of year or size of infestation. Consult Sound Horticulture for specific release rates and recommendations..


Before Pest Detected


When pests detected


Established populations


Fungus Gnats

Stratiolaelaps 25,000/L

50/m2, twice 34L/ha 2x 2-3 wk apart



Nematodes Bti (Vectobac)

follow label 3-4 applications 7-10 days apart

Western Flower thrips

Cucumeris 50,000/L

1,000,000/ha 100/m2,


100/ m2 in infested area

Orius After Feb.

0.25/m2, bi-weekly x 4

Two-spotted Mite




2-4/m2, weekly until on all mite infested leaves


20/m2 on all infested leaves



1/ m2, once 1/ m2, once
pollen present







100/ha, bi-weekly


100/ha, weekly x 4


Weekly, 100/hot-spot



0.15 m2 bi-weekly


0.2 m2, weekly x3


0.2 m2, weekly





0.2 m2, weekly x 3


2000/hot-spot, 10/m2 weekly







50-100/hot-spots weekly





1.5/m2, weekly x 4


4-8/m2, weekly X4/hot spot





100/h-spots weekly x 3


100-500/hot-spots, weekly





100/h-spots weekly x2







22/ m2, weekly

Btk (Foray)

Follow label




© Applied Bio-Nomics Ltd, 2004

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