Tuesday, April 3, 2012

NATURAL INSECT CONTROL IN THE GARDEN



The majority of insects you find in your garden are actually harmless and require no intervention. They are either nature’s helpers or food sources for nature’s helpers. For those insects that do pose a threat to some of your plants there are several non-invasive solutions you can utilize to prevent, monitor and control these pest insects.

This approach to pest management is called IPM or integrated pest management. Their premise is simple, begin with the least invasive and most environmentally sound treatments, gradually working your way up to the more invasive treatments (only if it becomes necessary).



The Benefits of This Type of Response to Pest Insects Includes:

  • Sustaining a healthy population of friendly insects that will serve to help keep the bad ones under control.
  • You will attract more pollinators to your garden thus producing more blooms, fruits and vegetables.
  • You be able to maintain a healthy soil microbial population, translating into healthier more disease resistant plants.
  • Garden edibles will taste better and be safer for your consumption.
  • You will not lose entire crops of vegetables to a single infestation.
  • You will also have fewer problems in the long run, as Mother Nature will perform much of the work for you.


A. The First Step of Integrated Pest Management is Prevention:

Your best line of defence is a good offence. Doing what can be done to prevent insect problems just makes good sense and it will save you both time and money in the long run. Some examples include:

Planting pest-resistant varieties where the pest is a problem:

Companion planting: By planting specific companions for your plants you may be able to help ward off insect attacks. Other benefits include improving the plants health and/or enhancing its flavour. There are several good books on the subject. (A couple that come to mind are ‘Roses Love Garlic’ and ‘Carrots love Tomatoes’.

Time you’re planting around insect hatchings: Some garden plants may be able to be planted after a particular problematic pest has run its course. If you have a problem with leaf-miners try planting susceptible plants from early June onward.

Eliminating structural conditions that encourage pests: Attract Beneficial Insects (like lady bugs, lace wings, parasitic wasps, tachinidad flies and praying mantis to your garden. You need these insects to control the pest insects and to pollinate your plants.

Draw on the services of other  mother nature’s helpers: Like birds, toads, bats and nematodes

Practicing good sanitation: While some garden debris is beneficial for adding organic matter to the soil and many insects prefer to munch on fallen debris over your plants; too much of a good thing becomes a bad thing. Too much debris invites pest insects and also provides a breeding ground for both insects and disease.

Create physical barriers:
  • Place toilet paper rolls/paper towel rolls around new seedlings to protect against cut worms.
  • Place floating row covers over spring vegetable crops.
  • Install netting over a fruit trees and berry crops, to protect them from the birds.
  • Install grease bands around the trunks of fruit trees (especially apple, plum, cherry &pear trees) to help prevent the females of certain wingless moths from climbing up the trunks to lay eggs.
  • Place sticky bands around the trunks of fruit trees to control ants that guard aphid colonies.
Control weeds: Many insects (both beneficial and pest) are attracted to weeds. Either as a source of food or a place to lay their eggs. Get to know your weeds and keep the bad ones pulled.

Choose natural fertilizers over chemicals: Chemicals upset the soil organisms that are instrumental in helping to control many pest insects.

Keep your plants healthy and well cared for: Pest insects tend to attack weak and sickly plants first.


b. Monitoring

Once you have taken the precautions you can to prevent pest insect outbreaks the next step is to monitor your garden and be on the lookout for potential problems.
    Yellow sticky tapes can be used to help keep an eye on insect types and populations.
  • Monitor your plants regularly. Watch for the first signs of garden pests, like holes, wilting, webs and color changes. Check the undersides of leaves. Check the branches. Look for eggs and nests.


 

 

 

 

c. Treatments

Identify the problem before treating it. Determine if it is just an isolated incident or a full blown attack. Is the pest still present or has it already been and gone. Once you have identified the pest and determined whether it warrants intervention following are a few natural treatments available to you.

Dormant oils: (Used for over wintering stages of mites, scales, aphids, and other insects).
The primary way horticultural oil kills insects is by suffocating them. The oil blocks the spiracles through which insects breathe. Horticultural  oils also disrupt the metabolism of insect eggs and the ability of some insects to feed, causing them to starve to death. Spray on dormant orchards and ornament plants to control the overwintering stages of mites, scales, aphids, and other insects. Temperature must be above 4-5 degrees C. (Caution: some plants are sensitive to this oil, like Japanese maples and blue spruce. Test an area on a plant first, and remember to spray before the plant brakes out in leaf.

Diatomaceous earth: is made of finely ground skeletons of small, one-celled creatures called diatoms. They are an effective treatment for slugs and other soft bodied insects.

Physical controls:
  • Hand picking works well for some of the larger, slower insects like: (slugs, snails, caterpillars, lily beetles and other pest beetles like June, Japanese and Viburnum leaf beetles) Drop the insects into a bucket of warm soapy water.
  • Remove and destroy pest insect eggs sacks and nests.
  • Hand squash aphids or blast them with the garden hose, careful not to damage your plants in the process.
Insecticidal soap: Useful against small soft-bodied insects such as aphids, mealybugs, spider mites, thrips, and whiteflies. This potassium fatty soap works in 2 ways.  It penetrates the insects cuticles causing cellular collapse and dessication. The oil content also serves to suffocate the insects.  Direct contact must be made with the best inorder for it to be effective. Some plants such as ferns, mountain ash, nasturtiums or japanese maples may be damged by the soap. It is always a good idea to test a small area first. Also note they should not be sprayed on hot days. Multiple applications are usually required.

BT (Bacillus thuringiensis): Is a soil-dwelling bacterium, commonly used as a biological pesticide. It is available in either a liquid spray or as a dust. It is an effective treatment against caterpillar infestations. When ingested by a caterpillar, the toxin affects it's digestive tract, causing it to quit feeding and die in a few days. Be careful when spraying and wear a mask.

Garden Sulphur: Effective for use as a fungicide. It can be used to treat powdery mildew, rust, black spot, scab, mites. Can be used as a powder or a spray. Do not apply when hot.

Some plants such as grapes, apple, pear, blueberry, currants, gooseberry, apricot, brambles and vines are senistive to sulphur.  Be sure to test an area first.
Neem Oil Products: Is a broad-spectrum insect poison, repellent, and feeding deterrent. It also stops or disrupts insect growth and sterilizes some species. It appears to be easy on beneficials and of low toxicity to mammals. Can be used as an insecticide or  fungicide. Dilute and apply as per manufactures instructions. (Full spectrum neem oil products will offer some systemic action.)

Homemade insecticides: There are many home made and natural recipes circulating out there. Check out the internet, especially the horticultural departments of some universities, organic gardening sites and of course your local Master Gardeners. You will find recipes for treating common problems such as black spot, powdery mildew, aphids and slugs, as well as recipes for general fungicides, miticides and pesticides.

Here are a couple of my favourites:

 
Cornell University Formula: (fungicide, miticide, or pesticide)
Basic ingredients:
2 tablespoons fine horticultural oil
1 tablespoon mild liquid dish soap (not detergent)
1 heaping tablespoon baking soda
1 gallon (4.5L) of water
Optional ingredients:
1 tablespoon or the equivalent of 8-8-8 fish emulsion/liquid seaweed (make sure your product does not contain sulphur)
5-7 droplets of a liquid plant vitamin mixture
Bacillus thuringiensis var. Kurstaki (Bt), at the recommended concentration (controls caterpillars)
*(You can apply this spray ever 2 weeks but you will probably find you only need to spray once a month.)
*(Try to use this spray solution before disease symptoms develop or as soon as you notice a problem.)

Baking soda: (good for powdery mildew)
1 teaspoon baking powder
1 L water
A few drops of mild liquid dish soap
(Put the ingredients into a spray bottle and mist directly onto the plant leaves, both sides.)
Measure carefully to much baking soda will burn your plants. Do not to spray on a hot day and test a small area on the plant first.

Pest Insects To Be On The Lookout For


Tent caterpillars: construct their silky tent like nests in early spring in the crotches of trees such as cherry (Prunus) and apple (Malus). They feed during the day, and at night, they return to the tent for protection. Your first line of defense should be to begin looking for these nests in early spring, about the time saucer magnolia (Magnolia x soulangiana) and crabapples are at bud break. Once located remove the nests and burn them, where permitted. Alternatively cut the tent open and hand pick the caterpillars throwing them into a bucket of soapy water. These 2 methods are most effective because large numbers can be removed at once. (Be sure to wait until they have returned to the nest for the evening before removing the nest).

Your second line of defense is spraying them with BT (Bacillus thuringiensis). Check for egg masses in the fall and spring and remove any you may find by scraping the clusters with a knife; prune trees in late fall or early spring also helps to keep populations low. Some natural enemies of tent caterpillars are birds and rodents. If physical and biological measures are not effective, use a pesticide which will have a minimal impact on both you and the environment. Apply dormant oil in late winter to kill the eggs before they hatch. An insecticidal soap is another option for control of the eastern tent caterpillar.

Slugs and Snails: In areas where slugs have posed a problem in the past till the area well or hand dig in the spring the reduce populations. Slugs prefer heavy, wet soils, particularly for laying their eggs. They also like weedy areas with plenty of soil spaces to hide in try to avoid such conditions. Sprinkling sand, ashes, broken eggshells and soot around vulnerable plants is a fairly effective deterrent, but they require constant reapplication (diatomus earth works in the same way). These barriers are scratchy and sharp serving to dry up the slugs mucous glands which are necessary for their movement. Hand picking still remains one of the most effective ways to reduce slug populations. Drop them into a bucket of warm soapy water or squash them under foot. Dusk and overcast days are the best times to go out picking. To encourage ground-living insect predators within the beds try laying down wooden boards. The predators hide under these during the day, emerging at night to perform their duty. As an added bonus slugs and slug eggs also collect there. Scrap them off into a bucket of warm soapy water once a week to further reduce your slug populations.


Viburnum leaf beetles: Only infest viburnums but they can nearly skelatonize the entire shrub. Adult females lay up to 500 eggs on viburnum twigs in summer and early fall. The eggs overwinter and hatch in spring. Larvae feed on foliage until early summer, then crawl down the shrub and pupate in the soil. Adults emerge from the soil in midsummer, feed again on viburnum foliage, and mate. From egg hatch to adult takes just 8 to 10 weeks. Egg-laying sites are easiest to spot when viburnums are leafless. Look for infested twigs between early October and mid-April and prune them out. This is probably the single most effective measure you can take to limit beetle populations.


Cut worms: Are a common pest of many vegetable crops. They consist of the larvae of several species of night-flying moths. Cutworms feed at night and will not generally be observed on plants or on the soil surface during the day, but you will know they are present by their characteristic damage, finding seedlings that have been ‘cut’ off at ground level. If you find this type of damage dig down around these plants to a depth of about 5 cm to find the cutworm(s) and destroy it/them. Cut worms lay their eggs on the soil; weedy areas, fields of grasses or pasture are ideal sites for cutworms to overwinter. Placing protective collars (like toilet paper rolls) around young seedlings is an effective way for the small home gardener to protect their young seedlings against cutworms.

Gypsy Moth: The European Gypsy Moth (Lymantria dispar), so named because of its ability to travel by attaching itself to various objects, is considered a major pest in North America. The caterpillar, or larva stage of the insect, eats approximately 500 species of trees. Broad-leaved trees are preferred, mainly red and white oak, poplar and white birch. The eggs hatch into caterpillars just as the tree buds are beginning to open and feed voraciously for up to 7 weeks. Therefore, it is important to control gypsy moth infestations early in the growing season.

When gypsy moth populations get out of control cities will often conduct an aerial and ground spray programs to control the outbreak. Btk (Bacillus thuringiensis subspecies kurstaki) is often used and is a safe and effective treatment for gypsy moths. Apart from large scale intervention there are many things the home gardener can do to reduce their populations. First and foremost is seeking out and destroying egg masses. Egg clusters are usually ¾” and oval in shape. They look like a piece of felt or velour and are buff colored when first laid but may bleach out over the winter months when exposed to direct sunlight and weathering. Common hiding places include the underside of branches, tree trunks, fences, firewood, outdoor furniture, swing sets, boats, and trailers and under the eaves of buildings. When an egg mass is observed it should be scraped off with a knife and dropped into a bucket. Destroy the eggs by burning, crushing or by pouring scalding hot water over them. The Asian gypsy moth, first discovered in the Vancouver area during the spring of 1991 is one to be on the lookout for in the near future.


Lily Beetles: eat the leaves, stems, buds and flowers of lilies, fritillaries and other members of the Liliaceae family.  They overwinter in the soil and come out early in spring. Do not mistake this beetle for the cardinal beetle which preys on other insects and is normally found on flowers at the edges of woodland. The lily leaf beetles have wings that are shinier with tiny dimples on them; they are more rounded in shape compared to the dull, narrow, flattened and elongated Cardinal beetle. Another difference between the two is their food preference. Lily leaf beetles are herbivores and are usually found on lily plants eating their leaves whereas the cardinal beetles are usually found on tree bark and flowers and feed on flying insects. Lastly, the cardinal beetle has comb-like antennae.
Lily beetles can be difficult to get rid of. Dormant oil may be used in early spring (before leaves are in bud) to suffocate the over wintering adults. Neem oil is also effective when applied to the early stages of larvae. Handing picking, knocking them into a bucket of warm soapy water, still remains the most effective treatment. It can be helpful to place a light coloured material beneath your lilies before picking as they tend to drop off when the plant is disturbed with their black undersides pointing up.

Soft- Scale: are typically found on woody and foliage plants. They feed on the sap causing yellowing of leaves and overall plant decline. They also secrete a sticky clear substance known as honeydew which provides the ideal environment for “sooty mold"; a fungus which can be more damaging than the scale itself. This honeydew also attracts ants which then carry the scale to uninfested plants as well as protect them from natural enemies such as predators and parasites. The first nymphal instar is called a crawler and has functional legs, while the remaining instars are attached to the leaf or twig and (with the exception of green shield scale) do not move.

Dormant oils and contact insecticides can be effective, but only if they are applied to the unprotected crawler stage of the scale. Thus, timing of contact insecticide application is critical to effective control. Parasitic wasps whose adults lay their eggs inside of soft scale may further serve to reduce scale populations. Metaphycus prefers young stages, Encyrtus the adult


Hard- Scale: differ from soft scale in that they generally have two or more generations per year. They do not produce honeydew and typically overwinter as eggs underneath the body of the dead female. (with the exception of euonymus scale which lay their eggs in early spring).They usually appear circular or rounded in shape and their crawlers tend to be less active.





Spider mites: Spider mites are common plant pests. They thrive in hot arid conditions thus irrigation and moisture management can be important cultural controls for spider mites. Symptoms of injury include flecking, discoloration (bronzing) and scorching of leaves. Injury can lead to leaf loss and even plant death.


Natural enemies include small lady beetles, predatory mites, minute pirate bugs, big-eyed bugs and predatory thrips


Ahids: They are a small, soft bodied insects with piercing mouth pieces that suck plant juices from
a wide varietyof plants. They vary greatly in size and colour . Damage includes spotty yellow leaf
discolourations, curling or distorted leaves and stunted new growth. As aphids feed they secrete
sticky substance called honey dew , providing ( in humid conditions ) the perfect breading ground for
black sooty mold. Insecticidal soaps and dormant oil are some what effective in controlling populations. Spraying them with a fast jet of water is also helpful. Lady bugs are a natural preditor.

Other treatments and interventions available to the home gardener include:

Sticky bands: (Late April-early May) Wrap your tree trunk with 2 widths of duct tape at about chest height from the ground. Then carefully smear tanglefoot around the center of the duct tape. The caterpillars will stick to the tangle foot and you can pick them of and destroy them.

Burlap cloth bands: (Late May-August)
Wrap a 3m band of burlap around the tree trunk. Tie it in the middle with a rope and fold the top ½ down. Caterpillars feed at night and hide during the day in shelters that protect them from the heat. They will congregate under the burlap. Destroy caterpillars that emerge from under the burlap late in the afternoon before they crawl back to the canopy to feed. They crawl down the tree in the early morning and look for a place to hide. (http://cms.burlington.ca/Page3964.aspx)

Natural predators:
Bluejay, blackbird, catbird, black-capped chickadee, crow, grackle, red-winged blackbird, nuthatch, oriole, chipping sparrow, robin, tanager, vireo, and woodpecker


Other Insect Control Tips:

  • Keep a healthy garden. Insects tend to attack weak, sickly and stressed plants.
  • Water regularly, so plants aren’t stressed by drought
  • Stake plants to keep them off the ground and dry.
  • Mulch to prevent splashing soil and pathogens onto plant.
  • Rotate your crops to prevent the problem from over-wintering
  • Remove and dispose of diseased or infested plants.
  • Remove all plant debris in the fall, so there is no shelter for over-wintering garden pests and spores.
  • Properly identify the pest and determine if it is just an isolated incident or a real threat. Sticky bands are useful for lowering pest populations and for monitoring how bad the problem actually is.

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