SHEET 470 – INTERIOR PLANTSCAPES
Interior Plantscapes and Tropical Gardens
Guidelines for Biological Control
Interior plantscapes are areas where plants are grown in an indoor setting. In addition to
traditional conservatories, this includes shopping malls, sports facilities, restaurants, and
public offices. The plants used in such settings are usually a variety of tropical and foliage
plants, with a corresponding variety of possible pests. Common pest problems
include soft and armoured scales, mealybugs, spider mites, thrips, aphids, whiteflies and
black vine weevils.
Using biological control is becoming increasingly popular in interior plantscapes because
few pesticides are registered for indoor use and because of public concern over air quality
and use of pesticides in such environments.
Most plants used in interior plantings are produced outdoors or under shade in warm
climates. This means that they can arrive with pest infestations. Ideally, plants should be
isolated for a period of acclimatization before they are set out in the permanent location.
During this time they can be watched for developing pests and treated if necessary.
Unfortunately, this is often not possible and plants may be moved to the plantscape
shortly after arrival.
Challenges for adapting the use of biological controls to plantscapes:
Pests may be present in low numbers that are not detected, or in soil stages that are not
visible.
Pesticide history of newly received plants is often unknown; plants may have residues
that inhibit the establishment of biological controls.
Plantscapes may have existing pest problems which will move onto the newly introduced
plants.
Prepare a Pest Management Plan
To manage pests successfully, it is a good idea to prepare a plan for preventing pest
introductions and using biological controls (for more details see Sheet 160).
Identify all present pest problems in each plantscape, as well as potential pests that
commonly occur on particular plants used in your plantscapes.
Inspect new plant material carefully for insect and disease problems upon arrival.
Obtain a list of pesticides applied within the last 6 weeks from the supplier.
Set up a monitoring schedule to inspect plants in the plantscape (usually done weekly in
warm months, less often in cool months).
Keep records for each plantscape of:
pest species and outbreaks (specific plants, environmental conditions, dates),
biological controls used (species, timing of release, dates),
pesticide applications (products, rates, application methods, dates), and
cultural and pest prevention practices.
Prepare a budget for managing pests. It is important to know ahead of time whether the
price of controlling pests is likely to cost more than renovating the plantscape by
removing and replacing problem plants.
© Applied Bio-Nomics Ltd, 2004
SHEET 470 – INTERIOR PLANTSCAPES
Determine which biological control agents to use. Identify target pests, review
information on biological control agents and choose species suited to the situation.
Choose a distributor and work with them to determine delivery methods, timing and
instructions on using the biological controls.
Correct imbalances between pests and biocontrols, using compatible pesticides to spot
spray, if necessary, to reduce pest populations.
Have patience. If pest populations are relatively low, biological control agents will quickly
develop a balance with the pest populations. Bear in mind, however, that although many
biological control agents become quickly established, it can take months to show their
effects. This is because it takes that long to for slow-growing plants to replace damaged
leaves.
If a severe outbreak exists, treat plants with registered pesticides, wait for the residues
to diminish and then reapply biological controls. In this case, it will take longer to
establish biological control of pests. Generally avoid using residual pesticides in the
month before introducing biological controls.
The following guidelines contain practical tips for achieving good results using biological
controls against pests in interior plantscapes. 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.
SOFT SCALES & ARMOURED SCALES
Black scale, hemispherical scale, brown scale and nigra scale are soft scale (Coccidae)
that attack many foliage plants. California red scale and purple scale are examples of
common armoured scales (Diaspidae). Some biological controls attack only particular
species of scales, therefore correct identification of scale is essential (for more on
scales, see Sheet 350).
Monitoring Tips
Close examination with a hand lens is necessary to detect scales. They often go
unnoticed until the honeydew they produce is conspicuous, or until plant growth is
stunted or distorted.
Release Biological Controls
Scale outbreaks often occur in early January or February, therefore biological controls
should be released in summer or by late November.
Predatory lady beetles feed on most soft scales whereas the wasp ‘Helvolus’ parasitizes
a limited number of soft scale species.
‘Rhyzobius’: Both larvae and adults of the small lady beetle Rhyzobius (=Lindorus)
lophanthae (see Sheet 280) feed on California red scale, purple scale, and other
armoured scales with a relatively thin scale cover. Optimum conditions are moderate
temperatures of 22-25oC (72-77oF). Excessive amounts of honeydew on leaves hinders
the movement of both adults and larvae, therefore spray leaves with water or soap and
water to remove honeydew before releasing beetles.
‘Harmonia’; The multicoloured Asian lady beetle, Harmonia axyridis , is an important
© Applied Bio-Nomics Ltd, 2004
SHEET 470 – INTERIOR PLANTSCAPES
predator of scales. It was originally used in China where releases of 200 adult Harmonia
per tree were reported to reduce pine scale by 87%. This predator is now mass-
produced by biocontrol companies and is available as larvae and adults (see Sheet
244).
‘Hippodamia’: Other field collected species, of lady beetles such as Hippodamia
convergens (see Sheet 244) may provide adequate control if they are released in large
numbers. Introductions of 10,000 to 30,000-1000 beetles at one time are recommended
to provide temporary control in plantscapes. Field collected beetle tend to migrate to
windows and disperse out open vents and windows. An insectary reared Hippodamia
convergensI is now available from some suppliers and will more reliably reproduce and
cycle in plantscapes.
‘Helvolus’: The tiny parasitic wasp Metaphycus helvolus (see Sheet 280) is effective on
a limited number of soft scale species, including soft brown scale, black scale,
hemispherical and nigra scale. Females lay their eggs in immature scales; optimum
conditions are warm temperatures of 22-29oC (72-84oF).
‘Aphytis’: One parasite available for armored scale is Aphytis melinus; it will attack
California red scale, San Jose scale, ivy scale and oystershell scale. Females lay their
eggs under the immature scale; optimum conditions are similar to Helvolus. Aphytis
parasites are quite delicate and often do not survive well if shipped long distances.
Other Measures
Prune out and destroy severely infested branches before releasing biological controls.
Mist plants with water to remove honeydew.
Spray infested plants with insecticidal soap to reduce scale numbers before releasing
biological controls. Soap is most effective on the crawler stage of scales.
MEALYBUGS
The most common species of mealybug in interior plantscapes is citrus mealybug. Other
species that may occur are long-tailed, obscure, citrophilus, grape and ground or root
mealybug. They damage plants by sucking the sap and their feeding causes distortions,
stunting and yellowing of foliage. They also produce honeydew, which supports the
growth of unsightly sooty molds on leaves (for more on mealybugs, see Sheet 350).
Monitoring Tips
Monitor the progress of biological controls by inspecting the new growth for signs that
mealybugs are disappearing
Release Biological Controls
Mealybug Destroyer: The lady beetle Cryptolaemus montrouzieri (see Sheet 250) is
most effective when mealybug numbers are high and when conditions are warm and
humid. They are most active in sunlight and are not as effective during dull winter
months. Several releases may be necessary, particularly during winter months.
‘Leptomastix’: The females of the tiny wasp Leptomastix dactylopii (see Sheet 280) lay
their eggs in mealybug nymphs and adults. They parasitize citrus mealybugs only,
© Applied Bio-Nomics Ltd, 2004
SHEET 470 – INTERIOR PLANTSCAPES
however, therefore correct identification of mealybugs is essential. Optimum conditions
are temperatures of 24-27oC(75-81oF).
Leptomastix complements the use of Cryptolaemus for citrus mealybug. The lady beetle
should be released first, to reduce high mealybug populations, followed by Leptomastix,
which is effective for low density mealybug populations.
Other Measures
Prune out heavily infested branches and destroy before releasing biological controls.
It may be necessary to control ants, which protect mealybugs from predators in order to
collect honeydew.
SPIDER MITES
Two-spotted mite, Tetranychus urticae (see Sheet 300), is the most common spider mite
in plantscapes; it feeds on a wide range of plants. Citrus red mite, Panonychus citri, is
less common, has a smaller host range, but can be damaging when it occurs; in addition
to citrus, this mite attacks palms, figs, ginger and bananas. In plantscapes, spider mites
are often a problem on foliage in the warmest and driest areas, such as in summer at the
top of tall plants nearest the glass. Their feeding causes white stippling on the leaves and,
in severe infestations, the leaves turn brown and collapse.
Monitoring Tips
Inspect leaves under 10-15 X magnification for signs of spider mite infestation.
Release Biological Controls
‘Persimilis’: The predatory mite Phytoseiulus persimilis (see Sheet 200) is an effective
control for two-spotted spider mites. It also feeds on citrus red mite, although may not
provide sufficient control. Introduce Persimilis at the first sign of spider mite damage, in all
infested areas. Distribute them on middle and upper foliage, preferably in early morning.
Monitor progress by inspecting new growth weekly to determine whether spider mite
damage continues to occur.
‘Occidentalis’: The predatory mites, Amblyseius fallacis and Galendromus
(=Typhlodromus) occidentalis (see Sheet 280) are more effective predator of citrus red
mite than Persimilis and can be used to control two-spotted spider mites. It does well
under high or low temperatures and is more effective than Persimilis in tree top foliage
and on hairy leaves. It feeds primarily on spider mite nymphs and adults, but not on
eggs. It is difficult to see this predator because it is so small, therefore watch for a
decline in the citrus red mite population to indicate the predator is established.
Other predator mites: At low two-spotted spider mite densities, Amblyseius californicus
(see Sheet 280) and Amblyseius fallacis (see Sheet 201) persist better that other species
as they feed on pollen and a variety of small insects and mites On woody ornamental
plants, introduce Fallacis predatory mites as well as Persimilis for control over a longer
period.
Other Measures
Mist plants frequently to raise humidity, but do not hose down the foliage, which would
dislodge predators. This slows the feeding and reproduction of spider mites while
© Applied Bio-Nomics Ltd, 2004
SHEET 470 – INTERIOR PLANTSCAPES
making conditions more favourable for predatory mites.
If spider mites populations are high, spray with insecticidal soap or fenbutatin oxide
(Vendex®) to reduce numbers, before releasing Persimilis; check compatibility table
(see Sheet 180) before using other pesticides.
THRIPS
Several species of thrips causes problems in plantscapes, including western flower thrips
(Frankliniella occidentalis) and onion thrips (Thrips tabaci)(see Sheet 320), banded
greenhouse thrips (Hercinothrips femoralis), echinothrips (Echinothrips americanus) and
other flower thrips. Thrips damage leaves and flowers by sucking the cell contents,
leaving a silvery, stippled and distorted appearance. Western flower thrips
can also transmit Tomato Spotted Wilt Virus, which kills some ornamentals and pesticide
resistant strains of this species are common.
Monitoring Tips
Use yellow or blue sticky traps at a rate of 1 trap/50 plants.
Use a 10-15 X lens to examine leaves and flowers for thrips or signs of damage.
Release Biological Controls
The following three species of biological controls are compatible and can be used
together to control flower thrips,onion thrips and greenhouse thrips Echinothrips is
difficult to control biologically due to its larger size, although Orius will feed on all stages.
‘Hypoaspis’: This soil-dwelling mite (see Sheet 230) feeds on the immature stages of
thrips in the soil or growing media. Hypoaspis alone cannot control thrips infestations,
but it contributes to the effectiveness of biological control when used with other
predators.
‘Cucumeris’: The predatory mite Amblyseius cucumeris (see Sheet 220) feeds on
immature stages of thrips as well as pollen. Cucumeris is available in a loose bran
carrier, which is sprinkled onto leaves, and in slow-release bags, which are hung on
plants. Release predators at the first sign of thrips, or, ideally, before thrips are present
on susceptible plants. It usually takes 4-6 weeks before changes in thrips numbers
caught on traps will be noticeable as a result of releasing Cucumeris.
‘Orius’: The minute pirate bug, Orius spp. (see Sheet 222) feeds on all stages of thrips.
Orius is only effective from March to September because they do not reproduce
if day length is less than 16 hours. Unless supplementary light is used, they 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.
Other Measures
Spot treatments with insecticidal soap can be used to suppress thrips “hot spots” before
releasing biological controls.
APHIDS
Green peach aphid, Myzus persicae (see Sheet 340), can be a serious problem in
plantscapes. Foxglove aphid, Aulacorthum solani, and potato aphid Macrosiphum
euphorbiae, may also occur. Aphids reproduce quickly on favoured host plants, causing
© Applied Bio-Nomics Ltd, 2004
SHEET 470 – INTERIOR PLANTSCAPES
distorted foliage; they also produce honeydew, which coats leaves and allows sooty
moulds to grow.
Monitoring Tips
Use a 10-15 X lens to inspect plants, weekly, for developing aphid colonies.
Release Biological Controls
All three biological control agents listed below can be used together for long term
control.
Release ‘Aphidius’ parasitic wasp (Aphidius matricariae) for control of green peach aphid
and Aphidius ervi for control of potato aphid (see Sheet 242), at low rates as soon as
low numbers of aphids are detected.
Release ‘Aphidoletes’ aphid midges (Aphidoletes aphidimyza) (see Sheet 240) between
March 15 and August 15, weekly, for all species of aphids (except gall forming species)
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 Sheet 244).
Other Measures
Prune out heavily infested branches; wash aphids off plants with a strong spray of water
or apply insecticidal soap sprays before releasing biological controls.
Control ants, which may be protecting aphid colonies from predators.
WHITEFLIES
The most common whitefly in plantscapes, is greenhouse whitefly (Trialeurodes
vaporariorum) (see Sheet 310). The feeding of immature whiteflies drops sticky honeydew
onto foliage below, which become covered with unsightly sooty mould. In high numbers
whiteflies also reduce the vigour of plants.
Monitoring Tips
Use yellow sticky traps to monitor for whiteflies.
Plants highly attractive to whitefly, such as Lantana, Jerusalem cherry or Fuchsia can be
used as indicator plants to detect early infestations of whitefly.
Release Biological Controls
The biological controls listed below are compatible and can be used together.
‘Encarsia’: Encarsia formosa is a tiny wasp (see Sheet 210) 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. Encarsia are less effective during cool weather and overcast periods and short
days of winter.
‘Delphastus’: Delphastus catalinae is a small, black, 1.4 mm (1/15 inch) long, lady
beetle (see Sheet 244). 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.
© Applied Bio-Nomics Ltd, 2004
SHEET 470 – INTERIOR PLANTSCAPES
Other Measures
If adults whiteflies populations are over 10/leaf, spot spray new growth (where adults
congregate) with insecticidal soap. Strong sprays of water can also be used to "blast"
adult whitefly and "strip" whitefly scale from the undersides of leaves.
BLACK VINE WEEVIL
Black vine weevils are dark brownish gray, 8 mm (1/3 inch) long “snout beetles”; they
are all females and they cannot fly. The adults are active at night; they chew half-circle
notches in the edges of leaves of various ornamentals. The larvae feed in the roots of
rhododendron, azalea, yew and other ornamentals and can stunt or kill plants.
Monitoring Tips
Check leaves for signs of new notches from May onward, which indicates adults are
present and will soon begin laying eggs.
Release Biological Controls
Insect parasitic nematodes: These nematodes (see Sheet 280) are very effective at
controlling root weevil larvae in plantscape conditions. They must be applied after the
eggs have hatched and larvae are present in the soil, usually from July onward.
Three soil drenches of nematodes mixed in water, 7-10 days apart, are usually required.
Nematode products vary, so always follow product recommendations for rates.
Other Measures
At night, when adults come out to feed, knock them off of plants onto ground sheets
where they can be collected and destroyed.
© Applied Bio-Nomics Ltd, 2004
