Integrated Pest Management

IPM Manual for Landscape Pests in British Columbia

Chapter 3: Preferred Pest Controls

Learning Objectives

When you have completed this lesson, you should be able to:

Describe the use of heat treatments and mulches to control vegetation.
Describe the use of sticky tree bands to trap winter moths.
List three groups of biological control agents used in outdoor landscapes and describe their target pests and uses.
State four characteristics of preferred pesticides.
Describe the mode of action and uses of the preferred pesticides: [Bacillus thuringiensis], boric acid, horticultural oils, insecticidal soap, pyrethrins, kinoprene, tebufenozide, fatty acid herbicide, [Agrobacterium radiobacter], sulfur, lime sulfur and ferric phosphate molluscicide.

Introduction

Treatments that suppress pests, while presenting the least risk to applicators and site users and doing the least harm to the environment, are preferable to those that have more toxic or broad-spectrum effects. Mechanical, physical and biological control agents (natural enemies) usually fit this description, as do some registered pesticides. This chapter describes:

selected physical and mechanical controls used in B.C.,
commercial biological control agents useful in landscapes, and
preferred pesticides for use in landscape IPM programs.

Mechanical and Physical Controls

There are many different mechanical and physical controls that may be used in landscapes. Examples of these are listed in the specific pest management chapters of this manual (see Chapters 4-10). Three mechanical and physical controls are described in greater detail below because they are of particular interest to pest managers in B.C.

Heat Treatment for Vegetation Control

Various systems have been invented to deliver high temperatures to kill the foliage of plants. They include: Hot water applicator

Flamers, which have been in use for over 50 years. Several sizes of hand-held propane torches are available, as well as tractor mounted flamers. Flamers produce temperatures of about 900ºC.
Hot water or low-pressure steam applicators, which have become more widely available since the early 1990´s. Most are large pieces of equipment, mounted on trucks or trailers, however, development of smaller and hand-held models continues. These deliver 100-200ºC water or steam to plant surfaces.
Infrared radiation applicators, which burn propane fuel to produce a radiant heat source. Equipment now available ranges from hand-held applicators for spot treatments of dandelions to hand-propelled and tractor mounted units for broader treatments.

Various models of the heat applicators described above are sold or leased by suppliers. Some service companies purchase the equipment and provide treatments on a contract basis. Much of this equipment is large and more suited to municipal or industrial use, however, hand-held flamers are widely available. Small infra-red applicators have recently become available in Canada.

Mode of Action: High temperatures tear apart plant cells and destroy proteins in the cells. It is only necessary to heat the leaf long enough to destroy the waxy cuticle of the leaf and disrupt the cells. Torching or boiling the plants until damage can be seen immediately is unnecessary and may stimulate re-growth of some established perennials such as morning glory. Effects of heating may be visible in as little as an hour or take up to several days to show.

Seedlings, annuals, young perennials and germinating seeds are most susceptible to heat damage. They are usually killed by a single treatment. None of the heat treatments penetrate into the soil or below a layer of gravel, therefore they do not kill the roots of established perennials. Perennials may require three or more treatments in a season to deplete the roots and kill the plant.

Broadleaf weeds are more easily damaged by heat than grasses are. The growing tips of grasses are encased in a heat resistant sheath, which makes it possible to selectively control weeds in turf using a flamer (but practice your technique in a low visibility area first!). Some other plants are quite susceptible to heat. For example, research in B.C. found that low-pressure steam killed Scotch broom with only one treatment. Use: Using heat to control vegetation is ideal where non-selective control is required, such as:

hard surfaces where any plant growth is undesirable (i.e., graveled areas, cracks in sidewalks and pavements)
where all vegetation must be kept very short (i.e., around fire hydrants, sign posts, utility poles, metal sprinkler heads and along fence lines)
for marking lines on playing fields and ball diamonds, which can be done using a narrow applicator head

With the right size of nozzle or head, some heat applicators can also be used to control weeds selectively in flower and shrub beds.

Where flamers are used, the risk of causing a fire or damaging plastic fittings, such as sprinkler heads, must be taken into account. When using the flamer, direct the hottest part of the flame (this is the cone-shaped area around the flame) at the weeds. Hold the nozzle above the plants and slowly pass it once over the plant.

Plants in dry conditions appear to be more susceptible to heat treatments than in cool and moist conditions. Weeds are most susceptible to heat when less than a few centimetres tall (the 4-5 leaf stage). This stage is when the roots are also killed by the heat treatment. In the cool, moist conditions of the coast, several treatments may be needed annually: one in spring to kill the majority of seedlings, followed by a treatment after fall rains cause another flush of germination. Regular treatment prevents establishment of perennials.

Mulches for Weed Control

Mulches are soil coverings of organic materials (leaf mould, compost, straw, shredded bark, pine needles, wood chips, sawdust) or various synthetic materials, such as plastic sheeting or landscape fabrics (geotextiles). A common combination in ornamental planting beds is a geotextile weed mat covered with a layer of bark or gravel.

Mode of Action: Mulches suppress weeds by blocking the light they need to grow. As soon as seeds germinate, the tiny plants must reach light or they will die. Some weed seeds won't even germinate unless they are exposed to bright light.

Mulches have other uses in plant beds, including holding moisture in the soil and moderating soil temperatures. Organic materials also add nutrients to the soil as they decompose and they keep the soil surface from becoming compacted. This makes it easy to pull any weeds that do manage to grow through the mulch. Organic mulches must be periodically renewed as they decompose.

Synthetic landscape fabrics designed for use in planting beds allow water through, while preventing seeds below the mat from germinating. Some heavier geotextiles are also designed for use under gravel or bark pathways. These may need regular maintenance, however, as enough soil can be tracked onto the gravel to allow grasses and other seeds to grow on top of the mulch.

Use: Mulches are well suited to perennial flower and shrub beds, where they can stay undisturbed around permanent plantings for years. Ideally, geotextiles should be installed at the time the bed is first planted. After the soil is prepared and the fabric laid down, plants can be set into the soil through slits in the fabric. After planting, spread bark, gravel or other surface mulches over the fabric. Geotextiles can also be installed around previously established plants — it just takes more time to cut and fit the fabric.

To be effective at suppressing weeds, organic mulches should be at least 10 centimetres thick for heavy, dense materials and at least 16 centimeters deep for fluffier, lighter materials. Shredded bark or wood chips laid over geotextiles, however, need only be deep enough to give the desired appearance because the fabric is controlling the weeds.

Mulches should be applied as soon as the soil is cultivated or disturbed because weed seeds brought to the surface start to germinate immediately. This means you should have mulch materials on hand and ready to use when beds are being planted or weeded.

Using fresh sawdust, wood chips or straw as a mulch will temporarily rob the soil of nitrogen as the materials decompose. This means that where such mulches are used around growing plants, it is usually necessary to dig in extra nitrogen fertilizer before applying the mulch. The nitrogen robbing effect can be used to advantage, however, to starve weeds in pathways and other areas where plants are not wanted.

Tree Bands for Winter Moths

In southern Lower Mainland, Vancouver Island and the Gulf Islands, the winter moth (Operophtera brumata) has been a problem for the last two decades. In the spring, the caterpillars eat the leaves, buds and flowers of apple, cherry, other ornamental and fruit trees and roses, as well as leaves of maple, oak, birch and elm. In Vancouver, experience has shown that Norway maple and some Japanese maple cultivars are particularly susceptible. Defoliation damage is a major source of complaints to parks departments in infested areas. Sticky tree bands

In the early 1980s a species of parasitic wasp and a parasitic fly were released by Agriculture Canada to provide biological control. Research has also discovered the important role native ground beetles play in preying on winter moth cocoons. In most years, these natural enemies largely keep winter moth numbers down on Vancouver Island. In Vancouver, however, and in other areas when moth numbers are high, additional controls are often necessary, particularly on boulevard trees.

Mode of Action: Sticky tree bands work well as a physical control because of the winter moth's peculiar biology. The adult moths are active in the early winter, which is when they mate and lay eggs. The female moths, however, cannot fly (it is the male winter moths that you see flying into car headlights in December). The females must walk up the tree trunk to lay eggs out on the branches, therefore a band of sticky glue around the trunk can catch them before they lay eggs. The bands are only needed between mid-October and late January, which is ideal to avoid harming beneficial insects and spiders that travel up tree trunks at other times of the year.

Use:

Start by wrapping a 15-cm wide band of cotton batting around the trunk to fill the crevices in the bark. This is to keep moths from crawling under the sticky band. The cotton layer is most important where there are high numbers of moths and on trees with rough bark.
Next, wrap a 15 to 20-cm-wide band of plastic food wrap or plastic sheeting around the trunk; several strips of wide plastic parcel tape can be used instead, wound around the trunk to make the same width. Plants with multiple trunks must be banded on each trunk; it may be necessary to band the plants next to susceptible trees as well, to keep moths from using them as another route up to the leaves.
Where moth populations are low or moderate, one band is usually enough. Place the band at chest height or wherever it is convenient, depending on the shape of the trunk. Where moth populations are high, traps rapidly fill up with trapped moths. In this case, use two bands, 15-20 cm apart on the trunk (plan to replace the lower band when moths start to be caught on the top band).
Spread a 10-cm wide layer of insect glue (Tanglefoot®, Stikem®) over the band, making sure there are no gaps. The glue can be applied with a spatula, putty knife or stiff brush and spreads more easily when it is warm. Spread the layer of glue as thinly as possible over the upper two-thirds of the band. This leaves some space on the band to catch glue that could drip onto the trunk below in warm, sunny weather.
Put the bands up in mid-October. Periodically check that they are free of leaves and other debris. Replace bands if they become full of trapped moths. Remove the bands and dispose of them in late January.

Biological Controls (Natural Enemies)

Releasing commercially reared biological controls is a well-established method of controlling pests in greenhouses and interior plantscapes. There are over 20 species of beneficial insects and mites commonly sold for this use (see Table 1). Only a few species, however, have been shown to be practical for releases outdoors. Generally, the most useful approach outdoors is conserving and attracting native beneficial species (as described in Chapter 1).

The following section describes commercial biological controls that can be used in outdoor landscapes. Although microbial products are biological controls, they are also registered pesticides, therefore are discussed later in this chapter under Preferred Pesticides.

Insect Parasitic Nematodes

Nematodes ("roundworms") are slender, tapering worms. There are thousands of species of nematodes: many attack plants, others break down organic matter, and there are beneficial species that attack insects. Although some nematodes are quite long ("horsehair worms"), most are microscopically small. Among them are the insect parasitic nematodes. To date, the nematodes available in commercial products have been species of Steinernema or Heterorhabditis, although others are under development.

Target pests: Various species of insect parasitic nematodes can be used to control the larvae of root weevils, crane flies (leatherjackets), fungus gnats and other turf and nursery pests. They have been used successfully in Toronto in tree bands to control elm leaf beetle larvae. Generally, Steinernema carpocapsae is better suited to webworms, cutworms, girdlers and wood-borers, while S. feltiae is more suited to fly larvae. Heterorhabditis megidis is now available for black vine weevil control. Other species particularly suited to control white grubs and other root weevils may become available in the future.

Use: Nematodes are sold in a dormant stage so that they survive storage and shipping. To apply them, the nematodes are mixed in water and applied to the soil. They can also be applied through irrigation systems. Since products differ, always follow application instructions with the product.

Nematodes are generally not effective in dry soil conditions. They are most useful in greenhouses, nurseries, and planting beds where regular irrigation keeps the soil moist. For outdoor use it is usually advisable to irrigate plantings well, both before and after the nematodes are applied, to soak them into the root zone. Nematodes are also not effective in cool conditions. Currently available species should be used when soil temperatures are above 12°C.

On potted plants, research has shown that overhead irrigation can wash the nematodes out of the soil within a month. Where changing to a sub-irrigation method for greenhouse benches is not feasible it may be necessary to apply nematodes more often to get good results.

Predatory Midges

The aphid midge, Aphidoletes aphidimyza, is a hardy, native insect that is reared commercially for use outdoors and indoors. Once released in an area they can become established for long-term control of aphids. They can be used along with the other species of native aphid predators that commonly attack aphids.

Target pests: Aphid midges feed on over 60 species of aphids, including all common species found in ornamentals and food crops. They are widely used in greenhouse vegetable production in B.C. and are also used in conservatories and interior plantscapes. They have been used successfully outdoors to control aphids in rose beds, boulevard trees and ornamental fruit trees.

Use: Aphid midges are sold in the pupal stage, usually in a carrier such as vermiculite. The carrier can be gently spread on the soil in the shade and kept moist until the adult midges have emerged. Alternatively, the containers can be held indoors until the first adults are seen, then opened and placed among the plants for a couple of days so the adults can fly out of the container.

The adult midges lay eggs among aphids on the trees and shrubs. The eggs hatch into tiny orange larvae, which feed on aphids for a week to 10 days. They drop to the soil to pupate and burrow several centimetres into the soil to spin cocoons. Adults emerge in 2-3 weeks. The last generation in late summer remains in the soil to overwinter.

Outdoors, Aphidoletes are usually released 1 to 3 times, 10-14 days apart, starting as soon as aphids are present on plants in the spring. They may also be released at the end of the summer if aphids are present on outdoor plants. This helps reduce the number of aphids that would lay eggs for overwintering. It also establishes an overwintering population of aphid midges that will be active early the next spring.

Lady Beetles

Adult and larva lady beetle Many different species of lady beetles are sold commercially to control soft-bodied insects and spider mites. Few, however, are useful outdoors (see Table 1 for species used in greenhouses). The convergent lady beetle, Hippodamia convergens, is the most widely sold, but its urge to fly away when released is a problem. The multicolored Asian lady beetle, Harmonia axyridis, is a better prospect (though not always available), because they do not have this instinct to fly away.

Target pests: Both lady beetles listed above are sold mainly to control aphids, although they will also feed on other small, soft-bodied insects.

Use: Hippodamia is usually not very useful in small areas outdoors unless it is prevented from flying away after release. The lady beetles are collected in California in the fall from large congregations of lady beetles that gather together to hibernate for the winter. When the beetles are released outdoors in the spring, their instinct is to fly away even though aphids are present. Some people claim success with keeping the lady beetles in the area by spritzing them with a clear soft drink when they arrive. The sweet liquid glues their wings together without harming them. This step may keep them around long enough to mate and lay eggs so that their offspring stay to control aphids.

Before buying lady beetles, however, consider that:

there are many native lady beetle species already present in B.C. and these cost nothing to provide aphid control, and
lady beetles (Hippodamia) are being scooped up out of their home range in large numbers to sell. This is not an ecologically sound practice and may not continue indefinitely.

Predatory Mites

Several species of predatory mites are available from suppliers. Most are used commercially in greenhouse vegetable crops, however, the native species, Amblyseius fallacis, is also useful in landscapes in B.C. This is because it is well adapted to the B.C. climate and can overwinter. Also, the commercially available strains are generally resistant to organophosphorous insecticides, although they are killed by synthetic pyrethroids. This means they can be released in landscapes and nurseries where some pesticide use is unavoidable.

Other species of predatory mites with limited application in landscapes are:

Phytoseiulus persimilis: an effective predator for spider mites in warm, humid conditions, where no pesticides are used; it can be used outdoors in the summer in special situations, but is not hardy enough to overwinter in B.C.
Amblyseius cucumeris: used mainly to control flower and onion thrips in greenhouse vegetables; it also feeds on cyclamen and broad mites, spider mites and rust mites on outdoor plants.

Target Pests: Predatory mites are mainly released in landscapes to control two-spotted spider mite, European red mite and other spider mites in trees and shrubs. A. fallacis also feeds on rust mites and other mites found on trees and can overwinter to provide early season control of mites.

Use: Predator mites usually come mixed in vermiculite or on pieces of leaf. To distribute the mites, place the leaf pieces or sprinkle the vermiculite throughout the foliage of plants. Apply higher concentrations to areas with spider mite infestations. For specific release rates and instructions, contact the supplier for recommendations.

Table 1. Biological Controls for Landscapes and Plantscapes

The following are examples of natural enemies sold commercially at the time of publication. This is a rapidly changing field, however, so always check with suppliers for product recommendations before ordering.

Pest Problem	Beneficial Species
For Outdoor Landscapes
Aphids	Aphid midge (Aphidoletes aphidimyza) Multicolored Asian lady beetle (Harmonia axyridis)
Spider mites	Predatory mites (Amblyseius fallacis & other species)
Root weevil larvae	Insect parasitic nematodes (Heterorhabditis megidis)
Crane fly larvae (leatherjackets)	Insect parasitic nematodes (Steinernema feltiae)
For Indoor Plantscapes, Conservatories, Greenhouses
Aphids	Aphid midge (Aphidoletes aphidimyza) Aphid parasitic wasps (Aphidius matricariae and A. colmani) Multicolored Asian lady beetle (Harmonia axyridis) Convergent lady beetle (Hippodamia convergens) Lacewings (Chrysoperla carnea, C. rufilabris)
Caterpillars	Parasitic wasps (Cotesia marginiventris, Trichogramma spp.)
Spider mites	Predatory mites (Amblyseius fallacis, Phytoseiulus persimilis and other species)
Whiteflies	Greenhouse whitefly parasite (Encarsia formosa) Lady beetle (Delphastus catalinae)
Mealybugs	Australian lady beetle (Cryptolaemus montrouzieri) Parasitic wasp (Leptomastix dactylopii)
Scale, soft brown	Lady beetles [Rhyzobius (=Lindorus) lophanthae, Chilocorus nigritus] Parasitic wasp (Metaphycus helvolus)
Thrips, onion	Predatory mites (Amblyseius cucumeris)
Western flower	Minute pirate bugs (Orius spp.)
Fungus gnats	Soil mite (Hypoaspis miles) Insect parasitic nematodes (Steinernema feltiae)

Preferred Pesticides

When it is necessary to use a pesticide, the first choice, ideally, should be a product that is least hazardous to people and the environment. In this manual, these are referred to as "preferred pesticides". They have one or more of the following characteristics:

present the least short- and long-term health risk to humans
have low impacts on non-target organisms (usually because of short residual effects)
are most specific to the target species
present the least risk to the environment during handling and disposal

Preferred products include microbial insecticides, which contain microorganisms that only attack certain insects, and insect growth regulators (IGRs), which disrupt insect hormone systems. Fatty acids, insecticidal soaps and horticultural oils are preferred because they only kill on contact and have no residual effects that would continue to affect non-target organisms. Botanical pesticides, such as pyrethrins, which are moderately toxic, are preferred because they have short activity periods, which minimizes their environmental impact.

The following section describes the characteristics and use of twelve currently registered preferred pesticides. Other pesticides registered for use on ornamentals should be considered only where preferred products or other types of treatments are not suitable or available. More information on using these products can be found in the Handbook for Pesticide Applicators and Dispensers and the current Nursery and Landscape Pest Management and Production Guide (see Further Reading at the end of this chapter).

Insecticides

Bacillus thuringiensis (BT)

BT is a microbial insecticide containing the naturally occurring bacteria, Bacillus thuringiensis. Hundreds of strains of BT are known to researchers — of these, the BT kurstaki strain (BTK) has been registered for use on caterpillars since the 1960s; the BT israelensis strain (BTI) is used to control mosquito and fungus gnat larvae. The most recently registered strain, BT tenebrionis, (BTT) controls larvae of some beetles.

Mode of Action: In general, BT produces spores and protein crystals that infect and kill insects. BTK grows in the alkaline gut conditions of caterpillars. This causes them to stop feeding almost immediately (within 2-4 hours), even though it can take another 1-3 days for the caterpillars to die. The bacteria are not toxic to other insects, animals and people. Residual effects are short, as the bacteria survive only a few days in the environment.

Formulation: BT products are sold as liquid concentrates or wettable powders. BTI is also available in a granular form that can be spread in water where mosquitoes breed.

Use: BTK is used to control a variety of leaf-eating caterpillars on ornamentals and food plants, both outdoors and in greenhouses. These include: cabbage loopers, cankerworms, cutworms, diamond back moth larvae, apple ermine moth, Bruce spanworm, imported cabbageworms, leafrollers, spruce budworms and tent caterpillars. BTK is usually most effective on younger or smaller stages of caterpillars.

BTI is used to control mosquito larvae in ponds. To apply BTI products to water bodies an applicator must be authorized by the Ministry of Environment, Lands and Parks under a pest management plan or permit. The only exception is for ponds (usually artificial) that are entirely enclosed on private property with no outlet to a ditch or stream. BTI is also registered for control of fungus gnat larvae in commercial greenhouse flower production.

Caterpillar

Caterpillar BTT is currently registered for control of Colorado potato beetles on food plants; it has been used experimentally to control elm leaf beetle larvae.

Since the target larvae must eat BT to be affected, it must be applied while they are actively feeding. It shouldn´t be used if rain is expected within the next 24 hours as the spores can be washed off the leaves before larvae have a chance to eat them.

BT is non-toxic to mammals and birds because the bacteria do not grow in warm-blooded creatures; the bacteria also do not harm fish, bees, beneficial insects, earthworms and other organisms.

Boric Acid

Boron is an inorganic chemical element. Borax, which contains boron, is mined from deposits in the earth. Boric acid and other boron-containing compounds (called borates) are manufactured from borax.

Mode of Action: Boric acid acts as a stomach poison. It is particularly useful in ant traps and other insect baits.

Formulation: Boric acid is available in dusts, baits and ready-to-use liquids.

Use: The main use of boric acid is for structural pests. In landscapes and conservatories, it is mostly used to control ants, particularly where ants are hampering biological control of aphids by protecting the aphid colonies from predators. Place boric acid baits along ant trails, but out of reach of children or pets. Do not apply boric acid around growing plants, trees or shrubs as it has a herbicidal effect and may kill plants or retard their growth.

Boric acid remains effective as long as it is present. The toxicity is low to people and animals.

Horticultural (Supreme) Oils: Dormant and Summer Oils

Mineral oils, emulsified in water, have been used on dormant fruit trees for over 200 years to control overwintering pests. Modern horticultural oils are highly refined and some products can be used during the growing season as well as while plants are dormant.

Mode of Action: Oils acts upon contact, by suffocation and by disrupting other physical processes. They are broad-spectrum insecticides and miticides, with no residual effect.

Formulation: Oils are sold as liquid concentrates to be mixed in water to form an emulsion.

Use: As a dormant spray, oils are used to control overwintering eggs of aphids and some moths, also mealybugs, pear and rose slugs, scales and spider mites. Dormant oils are used only after the leaves of deciduous trees and shrubs drop in the fall or before growth starts in the spring. They should not be applied when freezing weather is predicted or while foliage is wet. The spray should have time to dry before rainfall or heavy dew forms.

Dormant oils are often mixed with lime sulfur for the control of insects, mites and fungal diseases (see Sulfur, below).

As a growing season spray, horticultural oils are used to control mealybugs, rust mites, scales, spider mites and whiteflies. With some exceptions, summer oils can be used on evergreens, woody ornamentals, roses, fruit trees and bushes and shade trees. Oils are phytotoxic to some plants, such as apricots, blue spruce, maples, and ferns, therefore always check labels for a list of plants that cannot tolerate oil sprays.

Use oils only on healthy plants, not suffering from disease, heat or drought stress. Summer oils should not be used in hot weather (over 30°C), under dry conditions or when temperatures below freezing are expected within a few weeks. Horticultural oils have low toxicity for mammals, birds, fish and other wildlife.

Summer oils reduce the populations of beneficial insects and mites that are contacted by the spray.

Insecticidal Soap

Soaps to control insects are made from bio-degradable salts of fatty acids, similar to those in household soaps.

Mode of Action: Soaps acts upon contact on most insects and mites and their eggs, providing broad-spectrum control, but without residual effects.

Formulation: Soap products are sold as ready-to-use products and liquid concentrates. Some products contain insecticidal soaps mixed with an insecticide, usually pyrethrins.

Use: Soaps are most effective on soft-bodied plant pests, such as aphids, mealybugs, pear and roseslugs, psyllids, scales, spider mites, whiteflies and other insects. Soaps are registered for uses indoors and outdoors on food and ornamental plants. Because soap works only on contact, it is important to spray all plant surfaces thoroughly. Repeat applications may be necessary, but it is a good idea to limit the number of times soap sprays are applied to the same leaves. This is because soaps can damage leaves of some plants. Soaps are particularly phytotoxic to bleeding heart, crown of thorns, gardenia, horse chestnut, Japanese maple, maidenhair fern, mountain ash, poinsettias and sweet peas (always check label for plants that cannot tolerate soap sprays).

Soaps are not toxic to fish, birds and other wildlife, but will kill beneficial insects that are contacted by the spray.

Botanical Insecticides

Botanicals are pesticides made from active compounds found in certain plants. An advantage of botanicals is that they generally last a short time in the environment. Preferred botanicals include pyrethrins (from pyrethrum daisies) and azadiractins (from the neem tree). The latter is not yet registered in Canada, but products containing azadiractins and other active botanical compounds may be available in the future. Rotenone is a registered botanical, but it is so toxic when it is first applied that it is not recommended as a preferred pesticide.

Recent research in the US and Canada to find other naturally occurring active compounds in plants has come up with many promising plant compounds. Some have insecticidal and miticidal activity, others even have herbicidal activity. These are compounds found in common plants such as mint, thyme, cloves, soybean, peanuts, and Artemisias. Pesticides containing some of these ingredients are now available in the US and some may become available in Canada in future.

Pyrethrins

Pyrethrins are the active ingredients extracted from the pyrethrum daisy (Chrysanthemum cinerariaefolium).

Mode of Action: Pyrethrins are nerve poisons that provide broad-spectrum control of crawling and flying insects, without residual effects. Pyrethrins act upon contact, causing quick paralysis in insects. They are known for their quick ´knockdown´ effect and irritant effect that drives insects, such as thrips, out of hiding places.

Formulation: Pyrethrins are sold as ready-to-use liquids, liquid concentrates, and dusts; they are also formulated in mixtures with other insecticides and fungicides.

Many insects can detoxify pyrethrins and recover from exposure, therefore a synergist is often added to the formulation to help the pyrethrins work. Piperonyl butoxide, a common synergist, is derived from sesame. It works by inhibiting the activity of enzymes in the insect that normally detoxify pesticides.

Use: Pyrethrins are used to control aphids, caterpillars, flea beetles, leafhoppers, beetles, thrips, spider mites, stinkbugs, whiteflies, boxelder bugs, etc., on ornamentals and food plants. They are also used to control structural and nuisance pests, such as ants, earwigs, flies, mosquitoes, gnats and yellowjackets.

Pyrethrins are best applied in the evening or on a cloudy day; they should not be applied in direct sunlight or at temperatures over 32ºC. Pyrethrins are generally not phytotoxic, however, there are a few exceptions, such as maidenhair fern and delicate seedlings.

Pyrethrum and pyrethrins are moderately toxic to mammals and birds, but are highly toxic to fish and will kill any beneficial insects contacted by the spray. Avoid inhalation and contact with skin and eyes; skin contact or inhalation may cause allergic reactions in sensitive people.

Teminology

Pyrethrum refers to the dried, powdered, flower heads of the pyrethrum daisy.

Pyrethrins are the group of active ingredients found in the flowers. They are unstable when exposed to sunlight and last for only a few hours.

Pyrethroids are synthetic compounds made to resemble pyrethrins in chemical structure. They are more toxic to insects and more stable in sunlight than pyrethrins; they last for a week or longer in the environment.

Azadiractin (Neem)

Azadiractin is extracted from seeds of the neem tree (Azadirachta indica). The extract contains several active compounds that affect insects by repelling them, inhibiting feeding and by disrupting their development. It has very low toxicity to mammals and degrades rapidly in the environment. It is registered for use on ornamentals and food crops in the US, but not in Canada at this time.

Insect Growth Regulators (Juvenile Hormones, Chitin Inhibitors)

Insect growth regulators (IGRs) are insect hormones, or their synthetic mimics. The growth and moulting processes of insects are controlled by hormones. When insects are exposed to these hormones at critical times during their life cycle it interferes with their normal development. Two IGRs, kinoprene and tebufenozide, are currently available for use on ornamentals, with more IGRs expected to be registered in future.

Kinoprene

Mode of Action: Kinoprene acts by disrupting normal development of eggs and immature insects and also by sterilizing insects. At higher application rates it kills adult insects. Effects on insect populations are usually gradual, rather than immediate.

Formulation: Kinoprene (Enstar® is the only product registered at this time) is available as an emulsifiable concentrate to be mixed in water.

Use: Kinoprene is registered for use on aphids and whiteflies on ornamental plants in greenhouses (i.e., azalea, chrysanthemum, dianthus, fuchsia, geranium, hydrangea, marigold, pelargonium, petunia, snapdragon). As it may cause damage to blooms, it is best applied in the pre-bloom stage. Kinoprene sprays can damage some varieties of poinsettias and roses, therefore test spraying a few plants to check for damage is recommended before treating all plants.

Tebufenozide

Mode of Action: Tebufenozide mimics the action of insect moulting hormones, causing larvae to stop feeding within hours of eating sprayed leaves. It may take 3-10 days for larvae to die.

Formulation: Tebufenozide (Confirm® is the only product registered at this time) is available as a liquid concentrate to be mixed in water.

Use: Tebufenozide is used to control larvae of moths, such as codling moth, leafrollers, winter moth and other caterpillars on ornamentals and food crops.

It is non-toxic to bees and does not affect predatory mites, wasps and other beneficial insects.

Herbicides

Fatty Acids

Naturally occurring fatty acid compounds are used in production of soaps. In the right concentration they will kill the foliage of plants.

Mode of Action: Fatty acids kill the foliage of most plants upon contact. They act quickly, with results showing up within 2 hours. They do not kill the roots of established plants. There is no herbicidal activity in the soil and no residual effect.

Formulation: Fatty acid herbicides are sold in liquid concentrates and as ready-to-use sprays.

Use: Apply in spring or summer to actively growing weeds, less than 13 cm tall. Fatty acids are most effective on seedlings and annual plants, such as redroot pigweed, lamb's-quarters, corn spurry, mustards, chickweed and others. They also suppress or top-kill some perennials, including plantain. Repeat applications are required to kill established plants and perennials.

Products are registered for use outdoors around shade trees, nurseries, parks, sidewalks, driveways, mulch, fence posts, greenhouses and before planting grasses, ornamentals and vegetables.

Do not apply if rainfall is expected within two hours and avoid spray drift on desirable plants. Do not plant in treated soil for 3 days after treatment.

Fatty acids have very low toxicity to mammals and low toxicity to fish and other wildlife.

Corn Gluten Meal

A new, non-toxic herbicide made of extracts from food-grade corn gluten meal has been registered in the US. It works by suppressing the germination of weed seeds. Regular use on turfgrass has shown a 50-60% drop in weed infestation in the first year, with higher levels of control in later years. It is not currently registered in Canada, but may become available in future.

Dandelion Mycoherbicide

Researchers at McGill University in Montreal have discovered a strain of the fungus Sclerotinia minor that kills dandelions and other broadleaf weeds in turf without harming turf grasses. In suitable conditions, control of dandelions has been shown to be more effective and twice as fast as lawn herbicides containing 2,4-D, mecoprop and dicamba. Extensive work has been done on commercial formulation of the product, efficacy in the field and environmental safety. Registration is expected to be straightforward and it may become available in Canada within the next year or two.

Fungicides and Bactericides

Agrobacterium radiobacter

A. radiobacter is a beneficial species of bacteria used as a biological control for crown gall (A. tumifaciens) on woody plants.

Mode of Action: A. radiobacter controls crown gall by disabling the pathogen at the point of infecting the plant. It is applied as an innoculant to susceptible plants or seeds before exposure to the disease, usually to stock before planting out.

Formulation: The bacteria are contained in a dust formulation that is mixed with water to make a slurry. The slurry is used as a seed treatment or a root dip. Only one product (Dygal®) is currently registered in Canada.

Use: The product is used to treat woody plants susceptible to crown gall, such as roses, clematis, chrysanthemums, flowering Prunus spp., willow, juniper and other ornamentals. It must be used by staff trained to handle it correctly and to prevent even brief exposure to sunlight, which kills the bacteria. It may not completely protect plants if they are planted where infected plants were grown before.

A. radiobacter is non-toxic and does not harm mammals, fish, insects and other non-target organisms.

Sulfur

Products containing sulfur, a naturally occurring element, are sold for broad-spectrum control of fungi that cause plant diseases. Sulfur is also a miticide.

Mode of Action: The sulfur particles bind with fungal spores to prevent their germination. Sulfur does not have residual effects, therefore must be reapplied frequently to protect new foliage.

Formulation: Sulfur is available as ready-to-use and concentrated liquids, dusts and wettable powders.

Use: Sulfur controls black knot, black spot, leaf spots, powdery mildew, rusts, apple and pear scab and other fungal diseases. It also controls russet mites and rust mites. It is registered for use on foliage of roses, flowers, other ornamentals, as well as fruit trees and vegetables.

Use only on plants listed on labels as tolerant to sulfur. Some plants (such as Boston fern, melon, pears, etc.) may be injured by sulfur, therefore always check labels for phytoxicity information.

Sulfur should not be used when temperatures are over 24°C and not within 30 days of using either dormant or summer oil sprays. It has low toxicity to mammals and is not toxic to fish, birds and other wildlife. Sulfur does not harm bees, but is toxic to beneficial predator mites.

Lime Sulfur

Lime sulfur is a calcium sulfur compound that is a fungicide as well as an insecticide and miticide.

Mode of Action: Lime sulfur has broad-spectrum activity against fungi that cause plant disease. It also controls mites and some insects.

Formulation: Lime sulfur is sold as liquid concentrates to be mixed with water. It can be mixed with oil sprays for dormant applications only.

Use: Lime sulfur is used to control black knot, black spot, brown rot, powdery mildew, rusts, apple and pear scab, peach leaf curl and other fungal diseases. It is also used to control scales, spider mites, rust mites, aphids, mealybugs, peach borers and other insects. As a dormant spray, lime sulfur controls overwintering eggs of insects on fruit trees, bushes and woody ornamentals. Dormant sprays are more concentrated than growing season sprays and can be phytotoxic to dormant Viburnum spp. and some fruit and nut trees.

Growing season sprays are diluted to reduce phytotoxicity so they can be used on foliage of woody plants. Lime sulfur is phytotoxic to most actively growing plants, however, so use growing season sprays only on plants listed on label and at the correct dilution for this use.

Lime sulfur should not be applied when temperatures are above 26°C. It also should not be used within a month before or after oil sprays during the growing season.

Lime sulfur is moderately toxic to mammals and non-toxic to fish, birds, bees and other wildlife. It is toxic to beneficial mites.

Typhula phacorrhiza

Researchers at the University of Guelph have isolated a strain of the fungus Typhula phacorrhiza that is effective in controlling snow mold diseases caused by pathogenic Typhula spp. Most testing has been done in Ontario, however, some trials have been also done across the country. While it is not currently registered, the researchers are in the process of preparing the registration package for submission and hope to have a granular formulation on the market within a couple of years.

Molluscicide

Ferric Phosphate

Slug A naturally occurring mineral, ferric phosphate (or iron phosphate) has been recently registered in Canada to control slugs and snails. It is as effective as metaldehyde slug baits, but much less toxic to non-target animals and should be used instead.

Mode of Action: Slugs stop feeding immediately after eating ferric phosphate baits, then start to dry out. They may not die for several days, but damage from their feeding stops as soon as they take the bait.

Formulation: The ferric phosphate is incorporated into a granular pasta bait which is spread around plants where slugs are causing damage.

Use: Ferric phosphate controls slugs and snails. Unlike metaldehyde slug baits, ferric phosphate is not toxic to dogs and other animals and they are not attracted to it. It is non-toxic to birds, fish and other wildlife and does not harm ground beetles, earthworms and other beneficial organisms.