Winter Garden Care: To Spray or Not to Spray?

(Pic: Johan Gerber) Mealybug on agapanthus

From June to August is most likely the time of year for the best physical exercise in our gardens. It is that time of the year where we exercise the physical part of garden care where we sharpen our pruning scissors and whatever tools are needed to remove diseased and damaged as well as insect infested parts of plants where possible. Depending on your region; it is the most important time for pruning roses, deciduous fruit trees and various other plants as well as controlling winter pests on evergreen plants. For those of you that have no or very low infestations of insects like scale (red, pernicious, wax, black, etc.), Australian bug or mealybug, as well as mite species, you are the more fortunate in terms of safeguarding healthy populations of their natural enemies during the summer months. You are also more likely to be the one that has been more careful in what you have sprayed during the warmer time of the year to protect nature's pest controls. If you are one of the less fortunate, look back and make a list of pesticides you have sprayed. The chances are very good that what you have been spraying to combat destructive pests also wiped out their natural enemies. During the colder months the natural enemies of most pests are less active and that is then normally when populations like scale and mealybug increase. This is where winter spraying comes in, if necessary.

(Pic: Johan Gerber) Pernicious scale on rose stem

Scale species can be present all year round in most regions and is normally more of a problem in shady, protected areas and there presence is normally given away by ants running up and down the plants or nesting round infested plants. Scale infestations can be found on leaves, twigs, branches and fruit.

Of all options available to control scale, physical removal of infested plant parts during the winter months are one of the best. That is of course where it is possible to remove such parts. The use of pesticides should be to target infested areas which can not be removed. Once infestations are under control, nature's biological controls will stand a much better chance to keep populations low. A rose badly infested with pernicious scale that is already experiencing serious die-back should rather be replaced, serious spraying will be necessary to remove such infestations.

(Pic: Johan Gerber) Red scale on citrus branch

Mealybug normally occurs on twigs, branches, fruit and leaves. Many prefer secluded spots on plants and are many times hidden and not easily detected, unless looked for. For most gardeners infestations are high by the time they are detected. Populations can be found all year round and mealybug is known to be found on various varieties of container plants right through the winter, peaking into spring, after which their numbers can be kept under control by natural enemies. But, if natural controls are negatively affected by pesticide sprays, numbers will increase further towards late summer. The absence of many natural enemies make the winter months the ideal time for breeding, especially in protected, shielded areas of home gardens.

(Pic: Johan Gerber) Wax scale on evergreen Eugenia branch

Females of mite species (e.g. red spider mite) go into a resting phase during the cooler times of the year which is induced by aging of the plant or as a result of extreme cold. This resting phase can be terminated by high temperatures, or it can continue for several months during cool periods. Beneficial insects associated with spider mite control are ladybird spp, minute pirate bug, predatory mite, predatory thrips, spider mite destroyer, and western predatory mite.

All of the above said brings us to the main reason why many of you have been tolerating the smell of lime sulphur for many years. The main purpose for spraying lime sulphur or a mineral oil has been to kill over wintering stages of insect pests on plants during their dormancy period, especially after pruning. Today, many natural oil formulations are available which can also be sprayed onto new or young growth. Plant oil formulations like Margaret Roberts Organic Insecticide and Vegol contain canola oil and are designed to be used during dormancy as well as active growth periods of plants. Alternatively use mineral oils like Grovida Orchex or Efekto Oleum. These oil formulations can only kill small bodied insects like aphids, scale, mealybug, whitefly and red spider mite on contact with no secondary poisoning to beneficial insects and wild life and can be used on roses, fruit trees, ornamentals and edible crops. Oil formulations applied direct after pruning leaves a protective oil layer on wounds. If necessary a general fungicide like Copper Count-N can be added to the oil spray mixture for sanitation of pruning wounds.

If you can do without spraying by purely removing badly damaged, diseased and insect infested plants, the better. Spraying is only necessary when you experience specific insect and disease problems that can be controlled without removing the plant. What you do in winter will determine the health of your garden in spring. For more information send an e-mail to and visit www.gardencare.co.za . Have a wonderful winter!

Articles

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

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	Johan Gerber
	083 631 9952		0866465406
	Plot 17, Middel Road, Leeuwfontein, DINOKENG		P.O. Box 220, DERDEPOORT PARK, 0035
	www.gardencare.co.za / www.gardenguardian.co.za

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. GARDEN CARE PAGE