Biological Control of Garden Pests

Biological control is all about using the predators and parasites of a pest species as a method of control rather than dousing your plants in toxic chemicals that often do not discriminate between friends and foes. It has the obvious appeal of safeguarding not only yourself, but also your children and pets who are often oblivious to the risk of inadvertent contact with chemicals.

The key to success with biological control lies in understanding the way in which insect populations fluctuate according to their food supply. Plant pests build up rapidly when there is abundant food available and this will eventually attract their natural predators and parasites, however, considerable damage may be done before the pest numbers are reduced. The trick is to be observant and detect the pest early in the cycle and introduce the appropriate predator or parasite straight away in large numbers. There is a surprising array of beneficial organisms available in Australia that is listed in this article.

It is very important to identify the pest you are dealing with so that you can order the most appropriate biological control. Australian company ‘Bugs for Bugs’€™ has a particularly good website (bugsforbugs.com.au), with abundant photos and advice on how to best apply their biological controls as well as a listing of other Australian suppliers. Bugs for Bugs also supplies some excellent publications that are available through their website as well.

The company supplies:
Aphytis wasps for the control of red scale
Chilocorus beetles (for armoured scale)
Cryptolaemus beetles (for mealybug)
Green lacewings (general predators for aphids, mites, whitefly, scale, mealybug and moth eggs)
Trichogramma wasps (for various moths)

Predatory mites

Two spotted (also known as red spider mite) is one of the most devastating and widespread problems of a huge range of plants, indoor and outdoor, ornamental and vegetable, particularly in the summertime. A predatory mite (Persimilis) has had a long history of successfully controlling two-spotted mite in commercial situations. This predator is available to home gardeners through Sydney-based Beneficial Bug Company. French bean leaves that are home to a population of predatory mites are distributed throughout the foliage of susceptible plants such as roses. The predators should be put out at the beginning of warmer weather in spring or when damage from two spotted mites is first noticed.

Caterpillar control

One of the easiest and most effective biological controls available to home gardeners is based on a bacteria (Bacillus thuringiensis) that infects only the larvae (caterpillars) of moths and butterflies. It is commercially available as a product called Dipel ® that is a powder containing the bacterial spores. This powder is mixed with water and sprayed onto affected plants where the caterpillars ingest it as they feed. The spores germinate inside the caterpillar’s digestive tract and cause a virulent fatal disease that kills them within a day or so. The disease is completely non-toxic to all organisms other than the caterpillars.

Beneficial Nematodes

For many gardeners mention of the word nematode conjures up fear and loathing as the root knot nematode has long been a major problem for a wide variety of garden plants in both the ornamental and vegetable garden. Nematodes are microscopic worm-like creatures that abound in the soil and interact with the various other organisms they encounter there. CSIRO scientists have identified a range of nematodes that are very beneficial to plants in that they parasitise and kill various insect pests. The range of pests that can be controlled by these beneficial nematodes includes scarab (African black) beetle, black vine weevil, garden weevil, mole cricket and fungus gnat.

Of most interest to home gardeners is the control of scarab beetles that not only attack the roots of a wide variety of garden plants including lawns trees and shrubs as well as many annuals, but also produce nasty larvae (curl grubs) that live in the soil and destroy roots of the same plants as well.

Australian company Ecogrow (see contact details below) supplies these beneficial nematodes to the horticultural industry as well as to home gardeners. The nematodes are microscopic and are packaged in plastic containers that are emptied into a watering can where they are mixed with water and sprinkled around the base of the plant. The nematodes swim through soil water and enter the body of their particular host insect where they cause a fatal disease and kill the host in a matter of days. Organisms other than the insect host are completely unaffected by the nematodes.

Contacts:

Bugs for Bugs
Phone: 07 41654663
Email: info@bugsforbugs.com.au
Website: https://bugsforbugs.com.au/

Ecogrow
Phone: 1300 554450
Email: info@ecogrow.com.au
Website: http://www.ecogrow.com.au/index.html

Beneficial Bug Company
PO Box 436
Richmond NSW 2753
Phone: 02 45701331