Saturday, October 31, 2020

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Home Issue 37 Beware of aphids: Zap them now

Beware of aphids: Zap them now

By GEOFF MIERS

Warmer temperatures and lush new Spring growth have provided ideal breeding conditions for aphids, tiny destructive garden insects that are breeding prolifically at the moment.

Quick action can limit their numbers and damage to your garden.

These tiny critters can cause lots of problems and can seriously impact on plant health, generally being referred to as the lice of the plant kingdom.

They exist near the bottom of the food chain. They are sap suckers piercing the leaf of plants to tap into the sap stream and they breed prolifically when climate conditions are right – which is now.

One day there can be none, the next day a score or more and within a few days literally thousands can appear.

Daily inspections of the vegetable and flowering annual gardens along with examining fresh new growth on citrus trees and roses should occur now for the next few weeks until it really cools down.

At this time the aphides only produce females, they do not need to mate and can commence breeding literally instantly producing between 25 to 30 babies a day and these babies can again commence producing within a day or two.

It’s easy to understand how their numbers can explode even within a week.

One aphid one day, 25 the next, 525 the next, 13,125 the next, 328,125 the next, 8,203,125 day six and after a week it is possible to have 205,078,125 aphids in your garden after only one week … all from one little insect.

Total garden inspections should really occur as aside from many vegetables and flowering annuals aphids can be found on a range of local natives like the Desert Rose, exotics like the Pirie Winkle, roses, native grasses and even on water lilies.

Aphids can come in various forms and colours however they are very small, are often found on the underside of the leaf or at the new tip growth and when noticeable are usually visible in large numbers.

I have found tiny black aphids, small green aphids and larger reddish / brown aphids all this week.

Often a sticky substance may also be visible on the leaf before the aphids are noticed. This is called honey dew, it is a residue excreted by the aphids as they feed. Ants love this honey dew and often ants present on the affected plant is the first indication of the aphids’ presence.

Aphids in piercing the cell structure of the plant are damaging individual cells and this can lead to leaf distortion particularly on new growth as it develops.

Damage to flowers and fruitlets can also occur. Aphids can be responsible for example in the loss of literally an entire crop of fruit or citrus in its formative weeks.

Aphids can also carry disease and in moving over a plant may be spreading powdery mildew or other fungal diseases.

Aphids, as referred to previously, deposit a sweet honey like substance that can if it builds up on the foliage of a plant lead to sooty mould forming on the leaves.

This spoils the appearance of the plant and can in severe cases impact on the plant’s function thus impacting on the plant’s health. The black sooty mould literally blocks out the suns rays and limits the plant’s capacity to utilise the suns rays and impacts on the process of photosynthesis.

Aphids fortunately are relatively easy to manage, the key is being aware of their presence before they have done untold harm.

The exception is aphids on lily pads. Oils to smother the aphids will pollute the water and with fish so sensitive to insecticides they just can’t be used.

Attempt to knock the aphids into the water for the fish to feed on them, manually remove individual pads or if things get totally out of hand remove all lily pads and the problem will disappear before the new pads emerge.

On plants generally on the garden there are a number of strategies that may be undertaken. On first noticing the presence of aphids I generally use my fingers and physically squash them. This involves frequent monitoring at least daily.

Short sharp squirts with water from the hose may dislodge the aphids and they may not have the capacity to re-infest the plant.

White oil and Natrasoap are environmentally safe products that are most affective against aphids, these products effectively smother them. Neem oil is another most effective natural product that is fast acting and most effective against aphides although this product should not be used on food plants.

Anti-scale is also often suggested as a handy product to control aphides. This product is largely an oil based product although it does have as an active constituent Maldison  commonly referred to as Malathion. Use on ornamentals, not food plants.

For severe infestations where a quick solution is needed the home gardener may consider using Pyrethrum, a contact spray working within minutes of application which is a plus as it can be used on food plants and only has a withholding period of 24 hours as it breaks down quickly in sunlight.

In summary, be vigilant use your fingers first, and if numbers quickly explode look to one of the solutions offered above.

Be warned, often people notice aphids after they have passed. They notice the sticky honey dew and the shedded skins of the aphids, any treatment then is a waste of time and dollars.     

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