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TheVillage Gardening

Drought and aphids

Posted on April 22 2012 at 2:15:00 0 comments

Apple aphid

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Bartlett Tree Experts point out two of the dangers to plants and trees this spring.

Lack of rainfall over the 2011/2012 winter, coupled with hosepipe bans already starting to be enforced, has led to widespread concern regarding the potential of drought on shrubs and trees planted into our garden landscapes.

Lack of water greatly reduces the plant’s ability to manufacture food, which weakens the tree and limits future growth. Moisture stress also increases the tree’s susceptibility to harmful insect and disease pests that would not ordinarily attack healthy plants. Long-term drought eventually leads to branch dieback and tree decline.

Of main concern is the impact of drought on susceptibility to aphid attack. Aphids are small sap-feeding insects, generally 1-5mm long.  Damage to plants results from the effects of feeding upon young tissue, which weakens and distorts new growth.

Secondary effects result from fouling of the leaves and stems with honeydew which encourages the growth of a fungus known as sooty mould. Transmission of viruses carried from diseased to healthy plants on the aphid mouthpiece and in the aphid saliva is also a problem.

CONTROL

The main danger period for trees is from March-October and non-chemical control is seldom effective in these conditions.

Of the many insecticides available for use, to be effective they have to be applied before insect populations reach a certain threshold. This calls for careful examination of trees for the first signs of damage. If applied at the wrong time then either i) the damage has been done or ii) the predators of these insects are also destroyed by the insecticide.

Because the aphid life-cycle is quick and predator life-cycle slower in comparison there can be a rapid re-build up of the aphid population without any predators, ultimately leading to an subsequent increase of aphid damage.

0121 381 0579
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http://www.bartlett.com


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