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The Battle of the Bug

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The Battle of the Bug

By Rachel Vogan

Pest Control - or the Battle of the Bug is not an easy task. With the variety of plants in our gardens this means that we have to become familiar with a range of insects pests, and the best control methods. The key to protecting your garden is the correct identification of the problem. There is no point in treating your plant for insect damage if it actually has a disease instead.

A point to note is that there are some good insects in the garden, and by using insect sprays you will kill the good insects. Some of the good insects are ladybirds, bees and predatory wasps.

There are some simple ways in which you can identify insect pests, and also how you can limit them coming into your garden. One of the golden rules is that prevention is better than cure. Always look for the best environmental solution for your plants – such as relocating your effected plant, rubbing or washing of insects of the plant foliage and keep the surrounding areas of your plants free from debris and weeds that attract insects and fungi.

There are a number of common insect pests that are prevalent in the Summer months. Aphids, Whitefly, Slugs and Snails, caterpillars and Thrips, that will affect shrubs and plants. In your lawns the Grass Grub and Porrina will be active.

Aphids are suckers (big ugly green ones). They are soft bodied insects about 3 mm long, and are commonly a pale green colour depending on the species and time of year. They are attracted to soft tender leaves and foliage so you will often find them on the tips and shoots in the Spring and Summer. They feed by sucking sap out of plants similar in the way a mosquito sucks blood from a body. The damage that is caused can vary from distorted leaves and shoots, to twisting leaves and buds. Control methods vary on what you prefer to use. Commonly used sprays are Liquid Diazinon, Derris Dust and Shield and Mavrik, all of these work well and are widely available. For a non chemical approach you can use natural sprays, such as Beat a Bug, or try spraying the insects with a strong blast of water or use an insecticide soap.

Caterpillars are the larvae of moths and butterflies. Generally they have a hard head with a long soft body, with eight pairs of legs about 4-5mm long. They are chewers and will munch their way through their favourite plants very quickly, so early identification is crucial to prevent unsightly damage. Control methods recommended are Liquid Diazinon, Derris Dust and Orthene. For a non chemical cure use Beat A Bug when you can actually see the damage or when the caterpillars are not active. In the winter when the eggs have been laid, use Spraying Oil to prevent them hatching into Caterpillars next season.

Slugs and Snails are most active in the spring and autumn months. They feed mostly at night and in periods of cool damp weather. Control methods are easy – pellets are the most common methods and Quash is a fantastic product that is non toxic to cats and dogs. Alternatively, you could use Snail & Slug Pellets. The pellets should be spread when planting out all bedding plants and vegetables, as slugs and snails can decimate seedlings over night.

Thrips are very small insects with fine feathery wings. Generally they are a dark brown colour and 1-2 mm long. The tell tale sign of Thrip damage is the appearance of silvery leaves especially on a number of common shrubs such as Viburnum, Rhododendrons and Photinia. Thrips can also do a lot of damage to flower buds, but this is harder to detect. It can be heart-breaking to a keen gardener to watch flower buds of Gerberas or Lisianthus, for example, open only to discover unsightly blemishes caused by Thrips. These insects can be controlled by spraying with Liquid Diazinon, Super Shield and Mavrik. Thorough coverage up under leaves where Thrips live is important. For non-chemical control use Pyrethrum based sprays, making sure you get the spray under the leaves. If infestation is bad, non-chemical control will be difficult. Getting coverage down into flower buds can be difficult so a useful trick is to dissolve a small amount of sugar, approximately 1gm per litre of spray, and let stand for an hour or so, before you spray. Overnight is fine if you want to spray in the early morning. Thoroughly spray the infected plants and the Thrips will move out of the flower bud as they will be attracted to the sugar, and then they will ingest the spray.

Whitefly are small dull white moth like insects that like to live underneath leaves. You can often recognise you have them when you touch the foliage of a plant and you see them flying around. In the summer months they are very common on tomatoes, pumpkins and other fleshy leafed plants. Numbers build up rapidly especially in warm, sheltered conditions so spraying as soon as possible after the first signs is important. Whitefly can have a life cycle as short as three days under ideal conditions, so if you are having trouble getting Whitefly under control, spraying three times, three days apart is the best way to break their life cycle. Use Liquid Diazinon, Derris Dust, Target or Mavrik to control. For a non chemical alternative use Beat A Bug or a pyrethrum based spray.

Lawn Problems – it is easy to confuse grass grub and porrina as they are both Lavaes that live in the soil. But they are quite different – one adult is a beetle – Grass Grub, and the other is a moth – Porrina. But when they are doing the damage as a lavae they can be hard to identify you need to look at the damage to identify which lavae is the problem. Grass Grub – what a name! The adults are light brown beetles that develop from a creamy c-shaped lavae (or grub). It is the grub that causes the most damage. The Lavae feed on the roots of lawns and the adult beetle will attack other plants such as ornamental shrubs, trees and vegetables. In your lawn you may notice brown or yellowing patches, and if you scratch under the surface the roots will be brown and decaying. To control use a drench of liquid Diazinon or Soil Insect Killer.

Porrina are a group of moths, which infest lawns and farm pastures. The moths are dark brown with white markings. The lavae (young caterpillars) hide under the surface of the soil or under leaf litter. You will notice eaten leaves and the presence of worm like casts on top of the lawn. At night they emerge from their burrows to feed on grass and other plant foliage. They differ from a grass grub as they do not feed on roots. But Porrina feed on grass and foliage. Control is easy apply a granular insecticide, Liquid Diazinon and Soil insect killer as drenches.

Good luck out there fighting the Battle of the Bug. It’s not hard – just make sure you know what it is that you are trying to kill before you get out there with the sprayer.

For more help visit the Garden Doctor. Or check out the range of products from Kiwicare.