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Protecting plants from pests and diseases

However experienced you are as a gardener pests and diseases can attack your plants. Few or us like using chemicals to control them, so any means of prevention is always better than seeking a cure. Often good cultivation methods really help your plants to resist attack; a plant under stress is always more vulnerable. 

Keep your plants well fed and watered

Regular watering in dry weather and maintaining the level of nutrients available in the soil can really help your plants to resist disease during the summer months.  Plants that are dry at the roots are particularly susceptible to mildew, that grey, powdery fungal disease that suddenly appears on leaves, stems and fruits in late summer.  Often this is because the plants are in full growth and leaves and stems prevent any rainfall from reaching the roots.  Keep well-watered and you keep the leaves in better condition; more resistant to invasion by fungal spores.

Mildew is less common on windy and coastal sites because they have good air circulation.  It is prevalent in small, sheltered gardens and under glass, so good ventilation and removal of some of the leaves to promote air circulation helps.  

Plants with strong, healthy growth can be more resistant to disease. Liquid fertilisers are particularly beneficial during summer as the nutrients are quickly absorbed by the roots.  When applying granular or powdered fertilisers make sure they are worked into the soil and watered in thoroughly. A mid-summer application of rose fertiliser around your roses is really essential to give them that extra boost needed to keep them healthy after the first flush of flowers has exhausted the plant’s reserves. 

Create a barrier to pests and diseases 

In some cases a physical barrier is very effective in preventing attack. For example fine mesh or horticultural fleece placed around plants can prevent insects from feeding and laying their eggs. This is used on some vegetable crops such as carrots, to prevent carrot fly and brassicas to keep the cabbage white butterfly at bay.  

Barriers can also be effective when it comes to keeping fungal spores off plants.  A shelter over a peach or nectarine grown on a wall prevents winter rainfall from spreading the spores that cause peach leaf curl.  Growing tomatoes under glass or polythene usually prevents the ingress of tomato blight.

Vitax have developed a clever organic barrier that can be sprayed onto the plant to protect against insect pests and diseases. Vitax Plant Guard is an organic residual barrier that forms a coating on the stems and foliage removing bugs and preventing them from laying eggs. It also prevents fungal spores from germinating.  Made from finely ground seaweed in natural plant and fish oils it is harmless to bees and stimulates plant growth at the same time. 

It is available as a concentrate, perfect to use in the garden as a preventative spray on a host of vulnerable crops and ornamentals.  Spray vines, honeysuckles and vulnerable climbers from midsummer.  Keep mildew at bay in the border by spraying aster, monarda and other subjects that turn grey around flowering time.

As a ready to use it is perfect for the greenhouse and conservatory, especially at the end of the year when plants such as citrus and fuchsias are brought inside.  This is the time when spider mite invades the foliage and scale starts to breed on the undersides of leaves resulting in sooty mould. Regular spraying with plant guard can really help to keep these pests under control. 

Tip

Perhaps the most important factor in achieving control is vigilance: keep an eye open for problems and act quickly if you spot them. Also make a note of the time that problems develop; if you know when it is likely to happen you can be well prepared next season. 

Andy McIndoe

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