These are the pests and plant diseases threatening your garden in August – this is what to do if you spot them

Summer is the time when all of the garden pests like to appear and attach themselves to our plants and other things...

The heat speeds up breeding, so this helps them hatch and mature more quickly, which is why we see more of them about.

Our experts give us the lowdown on the top five destructive diseases and pests to look out for and what to do if you see them.

1. Vine weevil grubs

'Vine weevil grubs are the ones to watch most closely, especially in pots, where plants can suddenly wilt if the roots have been eaten away,' says Julian Palphramand, head of plants at British Garden Centres.

The larvae of weevil beetles (large pine weevil and white pine weevil) have a white C-shaped body and a brown head. They particularly love conifer stumps and roots, and they tunnel underneath the bark and feed on the inner tree tissues. The larger variety damages young trees, whereas the smaller variety likes leaf edges and potted plants.

Lucie Bradley, gardening and greenhouse expert at Easy Garden Irrigation, agrees, 'They are one of the most destructive pests to find in your garden. If your plants are looking sad, check the soil – easy in pots and containers by simply turning the pots over, and you will see the distinctive larvae amongst what's left of your plant's roots. What you also need to be careful of is bringing these grubs into your garden when introducing new plants – I’ve found them in pots from the garden centre when I’ve been transplanting pot-grown plants in early autumn.'

You can pick them off, but another option is to use nematodes and follow the instructions on the packet. We like Amazon's Nemasys vine weevil killer, £12.95 for a standard pack.

2. Earwigs

'In late summer and early autumn you will tend to see more earwigs in your garden as those which have hatched this year are now adults, and are either seeking food in the form of soft fruits or autumn flowers, as well as looking for places to shelter from the cooler weather now arriving,' says Lucie.

The thing with earwigs is that they can be useful – they like aphids, insect eggs and mites, but whilst they're munching on them they can equally be chewing on younger leaves too.

'Earwigs are nocturnal pests so if you see damage to your plants during the day the best way to reduce this is to set up traps at night,' advises Lucie. 'Something as simple as an upside-down flower pot filled with straw and positioned on a garden cane near your vulnerable plants will provide a post where they will shelter, and you can simply empty them in the morning.'

If that doesn't work for you, Amazon actually sell earwig shelters (who knew!) for £3.95, and it encourages them to stay away from your plants.

3. Shield bugs

Shield bugs are quite distinctive and one of the lesser 'pests' to deal with. 'Although not as serious, it’s worth checking any plants with ragged flowers, damaged leaves or unexplained marking, then clearing away debris and hiding places to keep numbers down,' suggests Julian.

However, the main reason you would want to remove shield bugs is the smell they can create when threatened according to Lucie. 'It's a strong odour if they feel threatened, you touch or squish them, although they don’t sting or bite. What you want to be mindful of is that they will be looking for somewhere to shelter as the weather gets worse and want to hibernate over winter ready for spring when they lay their eggs. Ideally you don’t want these stinky bugs choosing your greenhouse, shed or house as their over winter abode.'

The best way to prevent them is to block holes, seal cracks and check vents. Scent deterrents can be effective – you can make your own by buying a spray bottle (we like B&Q's, £2.50) and use a few drops of essential oils like peppermint (try Amazon's Nikura oil, £4.99) and mixing it with warm water. Spray where you think they are to repel them naturally.

4. Powdery mildew

Powdery mildew is a fungal disease that looks like flour spots on leaves, stems and buds. It's very common and loves perennials like roses, phlox, delphiniums and peonies; annuals like sweet peas, cosmos and sunflowers; and fruits like grapes, squash, and beans. You can also find it on lilacs and oak trees.

'You can try to decrease the risk of powdery mildew affecting your plants by thinning out crowded growth to increase airflow in plants,' says Richard Barker, horticultural expert and commercial director at LBS Horticulture. 'Ensure that plants are spaced apart for good airflow, and whenever you water plants, ensure that you are watering at the base instead of wetting the foliage to keep it dry.'

A natural way to treat this is by making a baking soda spray with water and a few drops of washing up liquid. If you prefer a ready-made option, then look at Amazon's EcoWidow antimould and mildew for plants spray, £15.99.

5. White rust

'White rust tends to be most prevalent in late summer and early autumn when temperatures start to cool,' says Lucie. 'What you need to watch for are small pale green or yellow spots on the top surface of leaves, and if you look on the underside you will find corresponding raised ‘blister-like’ forms of creamy-white. If left unchecked, these blisters will mature and release a chalky white powder which is then carried in the air to other plants.

Richard has some great advice to prevent white rust: 'Ensure that you are watering plants at the base, or water early in the morning so any wet foliage can dry properly. Spacing plants apart promotes good air movement and stops moisture from remaining on leaves, and if removing infected plant tissue, this should be disposed of in the bin, as composting can cause it to spread further.'

You can also spray neem oil on the leaves; it's a good natural way to stop it spreading. Amazon's premium neem oil can be used to kill insects and fungus naturally, £9.99 for 250ml.

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Good garden hygiene is key in keeping most pests at bay. Of course, we can never get rid of all of them, and that would also go against the ecosystem of our gardens, but keep it tidy and free from debris to prevent as many as possible from making themselves at home.