Guide to Spraying


Spraying hints and tips

Prevention is Better than Cure
It is always easiest (and best) to prevent garden problems, rather than having to restore damaged plants.

Remember you will never find every possible type of pest, disease, weed or other problem in your own garden in one go so don’t panic!

Plants can fail due to a wide range of different problems, sometimes more than one type of problem may be involved but it helps to know what sort of problem you are dealing with:

The type of pest will vary with the location of your garden, the range of plants you grow, the season and the local weather conditions. Insect pests are the most numerous and include those which feed on leaves, flowers, stems, roots or fruits, or by sucking the plant’s sap. Some pests even spread infections or other plant diseases as they move from plant to plant.

There are also many types of plant disease, caused by a wide range of pathogens (the disease causing organisms).  The main groups are fungi, bacteria and viruses.  In a garden, the majority of diseases are caused by fungi.  The range of plant diseases in your garden is also largely determined by the season, local weather conditions and the range of plants that you grow.

Like humans, plants need a wide range of different nutrients to grow and develop. It is possible to prevent deficiencies occurring by keeping the plant well fed, or, if symptoms develop, it is often possible to provide the plant with whatever it is lacking. 

Whether your garden is tiny or huge, rural or urban, weeds will always appear.  The main damage is caused by the competition they create – most grow and set seed very rapidly, and are hungry eaters and drinkers so quickly make it hard for the more mild-mannered garden plants.  Some weeds are annual and may be easy to remove by hand, or better still, keep out in the first place, but others, the pernicious weeds, are perennial and much harder to destroy.  Some perennial weeds have very long-lasting and resilient chunky roots, making them extremely difficult to kill. But despite all that, a combination of good gardening, and on occasion weedkiller use, weeds can generally be kept in their place!



Chemical Controls:

Useful Because:
• Rapid results.
• Some chemicals can be used to treat pests in hard to reach places (these are called systemic pesticides and they are carried in the plant sap from the area you apply them to other parts of the plant.)
• Systemic weedkillers can be use for treating weeds with chunky and pernicious roots.
• Most products have been extremely carefully tested and so should, if used correctly, be able to carry out the control you need efficiently and speedily, without posing a risk to other plants or animals.

What to sprayPests

Greenfly, Blackfly and other Aphids:
There are numerous different types of aphid in most gardens, and almost all plants may be attacked by one or more of them!  Aphids feed by sucking plant sap and cause a range of symptoms, including general stunting, weakening and poor growth, yellowing and distortion such as leaf puckering.  Some aphids may also cause dramatic colour changes eg the currant blister aphid.
Aphids may produce large quantities of sugary excreta (honeydew) as they feed which causes stickiness and often attracts a black sooty mould too.  Some aphids may also spread virus infections as they move from plant to plant and feed and this may cause serious weakening, yellowing and often death of the plant.

Sprayer treatment:
Spray with a suitable insecticide.  Systemic products may be particularly useful on extensive or hard to reach infestations as these chemicals are carried in the plant sap from the area sprayed to other areas of the plant.



Caterpillars are the young or larval stage of butterflies and moths. There are a lot of different caterpillar pests in gardens, and they vary enormously in size and colour. Most feed on leaves, sometimes causing extensive defoliation, and some feed in large groups, often underneath protective webbing. A few caterpillar pests feed below ground, on plant roots eg the cutworms and some feed within fruits eg codling moth caterpillars.

Sprayer treatment:
Use a suitable insecticide spray as soon as you see signs of the caterpillars or their damage, and repeat as necessary.

Fungal problems:

Powdery Mildews
White or sometimes off-white powdery patches develop on just about any above ground part of a susceptible plant, especially the leaves.  The fungal growth may restrict normal expansion of the plant and so also cause symptoms of puckering and distortion, or, when fruits are attacked, they may split open.  Affected leaves may then start to yellow and may fall early.  Heavy levels of infection, especially when they occur several years in succession may cause serious loss of plant vigour.

Sprayer treatment:
Spray with a suitable fungicide.



Bright orange, dark brown or occasionally light brown spores develop, most commonly on the lower leaf surface but occasionally elsewhere.  The spores may be within clearly defined pustules, sometimes arranged in distinct patterns.  Infected leaves may yellow and later die, sometimes with seriously debilitating consequences, especially if infections are heavy for several years in succession, or if they occur early in the growing season.  Some types of rust have more than one type of spore, and these may vary in colour.

Sprayer treatment:
Consider applying a suitable chemical, making sure that you spray both the upper and lower leaf surfaces.

Leaf spots
Fungal leaf spots, as their name suggests, cause spots or areas of discolouration on the leaf surface.  The size, colour and shape of the spot varies with the plant and the fungus involved, but many are brown, black or reddish.  On some numerous tiny dots are visible on the spot too.  If the infection is heavy, the spots may coalesce, forming rather more irregular areas of discolouration.  Some leaf spots, such as black spot of roses, may cause serious damage as infected leave soon fall and the plant becomes weakened.  Other leaf spots are of much less significance and do not cause serious damage in their own right, usually only developing on a plant which is lacking in vigour. 

sprayingSprayer treatment:
Keep the plant well fed and watered and give it a bit of extra TLC so that it is less prone to attack.  Spraying on a foliar feed or seaweed solution may help to perk the plant up if applied in spring or very early summer.  Seek out resistant varieties, where available.

If this does not work consider spraying with a suitable fungicide if you have determined that the leaf-spotting is potentially damaging.  Spraying with a foliar feed may help to boost the plant’s overall vigour.

Tomato and Potato Blight
Greyish brown patches develop on the foliage and stems, sometimes followed by white, fluffy fungal threads.  The entire plant may collapse and die.  Infected potato tubers develop gingery brown discolouration and will soon start to rot.  Infected tomato fruits develop gingery brown to black patches of discolouration which spread into the flesh, and soon rot.  Blight is especially troublesome in warm, damp years. Very common on outdoor tomatoes.

Grow resistant varieties where available.  Grow tomatoes under cover in a greenhouse or frame as infection is only common when they are grown outside. Avoid wetting the foliage unnecessarily as this will encourage blight spread and development.

Sprayer treatment:
Where feasible, consider spraying with an organic treatment before the symptoms appear.  If blight attacks, remove all infected plants promptly.  Cut potatoes haulms (stems) down to ground level and bin or burn as this should prevent the tuber infection.

Magnesium Deficiency

Yellowing develops between the leaf veins on magnesium deficient plants, and there may also be yellowing around the leaf edges.  As the green pigments in the leaf are broken down, other pigments may appear, so instead of yellowing between the veins, bright red, mauve or brown colouring appears.  The older leaves are generally affected first, whilst the young leaves may remain good and green. Magnesium deficiency is most common if plants are grown in very acidic composts or soils, after periods of heavy rain or watering (magnesium is easily washed out of the soil) and when a plant has been fed with high-potash fertiliser (the potassium may make the magnesium unavailable to the plant).

Avoid excessively acidic composts and overwatering.  Use high-potash feeds when necessary, but not excessively and be prepared to either ignore the symptoms, or treat the plant. 

Sprayer treatment:
For the most rapid response, spray the foliage with a solution of Epsom Salts at about 20g in 1 litre of water to which you have added a wetting agent, then apply every 14 days.

Lime-induced Chlorosis
This develops when lime-hating plants (also known as acid-loving or ericaceous plants) are grown in a soil or compost which is not sufficiently acidic. It is usually combined with a deficiency of manganese and affected leaves show yellowing between the veins and sometimes yellowing or browning around the leaf edges. The newest and youngest leaves are generally affected long before the older, larger leaves.  

Avoid growing lime-hating plants in a soil or compost which is not sufficiently acidic.  Avoid using alkaline mulches but use plenty of acidic materials such as composted bracken or conifer bark chippings.  Water with rain water if you garden in a hard water area.

sprayingSprayer treatment:
As above, but also treat affected plants with a chelated compound which contains the materials they are lacking, in a form in which they can take them up and feed with a fertiliser formulated especially for lime-hating plants (such as). 

Japanese Knotweed
This is one of the most invasive and difficult weeds to deal with.  Given time, it has the potential to take over a garden.  The tall stems with their pretty, heart-shaped leaves and white flowers may look quite attractive but don’t be fooled - this plant makes it very difficult for other plants to survive and on some circumstances may even cause structural damage too !

The roots may go down to several metres below the soil surface so complete physical removal is extremely difficult in most situations.  However, regular digging out of the emerging stems will weaken the plant to some extent, but can be back-breaking, time-consuming and soul-destroying work!  If the shoots start to emerge from beneath a lawn or other grassed area, regular and frequent mowing will also weaken it with time. Always check any imported topsoil very carefully before using in your garden, as even a small fragment of the weed’s root may develop into a full blown infestation.

Sprayer treatment:
Treating the cut stems with a systemic herbicide (weedkiller) and spraying the foliage with a systemic product will have a weakening effect, but even with serious chemical onslaught, total control is extremely difficult to achieve.

Also commonly known as equisetum, this rough-textured plant has pretty whorls of stem-like jointed leaves. Horsetail has been around since before the time of the dinosaurs and there in lies a warning : it is extremely difficult to eradicate! It has also been seen many metres below the soil surface, and this too helps it to thrive.  Given the opportunity it will soon form a thick swathe of growth and out-compete garden plants.

Regular digging out or cutting back to ground level of the stems will weaken a horsetail plant, but this is rarely enough to kill it as it simply comes again from the bits left deep in the soil.  Regular and frequent mowing also help to weaken it, and it is sometimes possible to eradicate it from a lawn in this way.

Sprayer treatment:
In addition to first weakening the growth of an infestation of horsetail as suggested above, it may be possible to weaken it further by spraying with a suitable weedkiller treatment. Gently crushing the plants, so that their tough surface is slightly damaged, but the plant is not severed, may help weedkiller solutions to penetrate. As a safety precaution, always cover nearby garden plants before spraying.
With its fast twining stems, attractive heart-shaped pale green leaves and delicate trumpet shaped flowers, you could be forgiven for thinking that bindweed was really rather lovely.  But the speed at which it grows and its ability to virtually smother smaller and slower growing, more delicate plants combined with its ability to compete very strongly, make bindweed a force to be reckoned with.

Regularly and frequently remove the twining stems and dig up the roots, taking care not to damage your plants in the process.  Even a short segment of bindweed left in the soil is likely to sprout and form a new plant, so regular and frequent forking out and uprooting may well be necessary.

Sprayer treatment:spraying
In areas where you have no plants you wish to keep, spraying with a systemic broad-leaved weedkiller (such as) will generally kill off a high percentage of the bindweed infestation. Within established beds and borders chemical treatment is a lot more difficult – it may help if you install a support system or even just a few bamboo canes and encourage the bindweed to scramble on to the support and out of the bed or border where it may be possible to treat it without endangering the garden plants. As a precaution, always cover nearby garden plants before spraying.

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