Predatory Ladybirds: Nature’s Solution to Aphid Control by Johan Gerber
Predatory Ladybirds: Nature's Solution to Aphid Control by Johan Gerber
(Pic: Johan Gerber) Adult lunate ladybird (insect predator), feasting on rose aphids
With spring round the corner it is time to make sure that gardeners are going to follow healthy gardening practices to enhance and conserve Nature's biological controls. Starting with predatory ladybirds, one might assume that all ladybirds are beneficial. Unfortunately there are a few non-beneficial species which are plant-eating. The potato ladybird is quite often mistaken for its beneficial look-alike, the lunate ladybird. Beneficial ladybird species do not cause damage to leaves like the potato ladybird and the sweet potato ladybird.
Although cypress aphids do a great deal of damage to conifers, there is a positive side to the infestations in my garden. Aphids attract beneficial insects such as ladybirds and praying mantids during the winter months. I am always delighted to see ladybird couples mating in June and July in the dense foliage of my golden rocket which tends to become badly infested with cypress aphid. The challenge is to reduce the cypress aphid population without killing the ladybirds and praying mantids.
(Pic: Johan Gerber) Adult potato ladybird ( leaf-eating sp) with damage to leaf showing
It is always good to allow a small number of aphids to survive on your plants in the garden. I have found that the best way of controlling severe infestations of aphids without affecting healthy numbers of beneficial ladybirds on my roses is to remove part of the serious aphid-infested new shoots or growth. Once the shoots and flowers mature, the aphids leave anyway. When these aphids or any of the other food sources leave the plant, the ladybirds also leave. Therefore to ensure healthy populations of beneficial ladybirds you need to make sure that host plants of aphids are maintained or alternative prey such as mealybug and red spider mite are still around.
Plants associated with beneficial ladybirds are fennel, dill, tansy, bishop's weed, angelica, Queen Anne's lace, golden rod, coreopsis, cosmos, dandelion, sunflower, crimson clover, hairy vetch, grains and indigenous grasses, buckwheat, butterfly weed, euonymous, rye, Hemp sesbania, soapbark tree and buckthorn. Most of the beneficial ladybird species in my garden visit the roses, golden rocket, sunflowers, lemon geranium, coreopsis, hibiscus, cosmos, shasta daisies and wild rocket.
(Pic: Johan Gerber) Adult black-ringed ladybird feasting on cypress aphids inside conifer (predator)
The control of ants nesting in soil around plants will help beneficial ladybirds control their prey more effectively. Ants, especially pugnacious and other 'cocktail' ant species, protect insects such as aphids against natural predators in return for honeydew. If you do use an ant control formulation, do not spray the plants but rather pour diluted spray mixture down their nest entrances.
Avoid the use of any insecticide, chemical or organic, that contains active ingredients for the control of beetle species such as astylus, CMR, flower, chafer, snout as well as stinkbugs. Many insecticides containing cypermethrin, deltamethrin, permethrin, bifenthrin, alpha-cypermethrin, chlorpyrifos, mercaptothion, gamma-BHC, fenitrothion, cyfluthrin, nicotine, rotenone and natural pyrethrins might kill adult ladybirds on contact.
(Pic: Johan Gerber) Adult spotted ladybird (predator) on rose leaf
The following active ingredients used in insecticide formulations are harmless or unlikely to harm beneficial ladybirds: Bacillus thuringiensis subsp. israelensis for fungus gnat and mosquito control; Bacillus thuringiensis var. kurstaki for the control of leaf-eating caterpillars; spinosad for thrips, African (American) bollworm and leaf miner control; garlic and essential oils used as insect repellents; etoxazole for red spider mite; pyriproxyfen for whitefly; potassium salts of fatty acids and canola oil for small soft-bodied insects and natural pyrethrins used as a nest treatment for the control of ants and wood-eating termites. Insect traps designed to be used with sex attractants (pheromones) will have no adverse effects on predatory ladybirds, unless it come in accidental contact with sticky liner or insecticide treated baits used. These traps and pheromone will soon become available for use in home gardens. Visit www.insectscience.co.za for information on this wonderful technology which will soon be available to home gardeners. Watch the press!
Baits containing fipronil for harvester termite control as well as granular baits for snail, slug and cutworm control will not affect ladybird populations adversely. Fungicide formulations containing plant organic acids, mancozeb, chlorothalonil, procymidone, Trychoderma spp., copper-based formulations and soil-applied microbial formulations will not harm ladybirds when used as directed.
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From: The Garden Guardian's guide to environmentally-responsible garden care.
Pictures : Johan Gerber
Snail and Slug Control in Harmony with Nature / The Living World Within Roses / Inaugural IPM-endorsed training courses will commence this month. / Garden Plants Perfect for Attracting Beneficial Insect Parasites and Predators / The Living World of Conifers / Winter Garden Care: To Spray or Not to Spray? / Spiders and Pesticides / Cold Blooded Wildlife: The Gift of Nature / Predatory Ladybirds: Nature's Solution to Aphid Control
Author: Johan Gerber
People who have the privilege of owning and tending a piece of land or garden earn with that privilege a significant responsibility.
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Garden care advice to consumers on the use of agricultural remedies ( pesticides).
Biopesticide product development for registration with Act 36 of 1947, Department of Agriculture.
Garden talks and editorial contributions to consumer magazines.
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