Beware the Bugs! Common Allotment Pests in May

May is one of the busiest and most exciting months on the allotment. Seedlings are racing away, potatoes are pushing through, beans are climbing, and brassicas are beginning to establish strongly. Unfortunately, gardeners are not the only ones enjoying the warmer weather.

As temperatures rise, many common allotment pests become far more active, and if left unchecked they can quickly damage young crops. The good news is that most problems can be managed naturally with regular checks and early action.

Here are some of the key pests to look out for on the allotment during May and the best ways to deal with them.

Caterpillars

May is the time to start watching for caterpillars, especially on brassicas. As butterflies become more active in spring, they begin laying eggs on crops such as cabbage, kale, broccoli, cauliflower, and sprouts.

At first, the damage can seem minor, but once caterpillars hatch they can rapidly strip leaves and weaken plants.

Signs to look for:

Small holes appearing in leaves
Yellow eggs underneath foliage
Tiny green caterpillars hiding along leaf veins
Black droppings on leaves

What to do:

Inspect brassicas regularly, especially underneath leaves
Remove eggs and caterpillars by hand
Cover crops with insect-proof mesh or netting
Encourage birds into the allotment
Grow sacrificial plants like nasturtiums nearby

The earlier you spot them, the easier they are to control.

Slugs and Snails

Young seedlings are especially vulnerable in May, particularly during damp nights and after rain. Slugs and snails love tender new growth and can wipe out freshly planted rows overnight.

Beans, lettuces, courgettes, dahlias, and brassicas are favourite targets.

Signs to look for:

Ragged holes in leaves
Slimy trails
Seedlings disappearing overnight
Damage appearing mainly in the morning

What to do:

Check plots at dusk and remove slugs by hand
Water in the morning rather than evening
Use wool pellets, copper tape, or crushed eggshell barriers
Encourage frogs, birds, and hedgehogs
Reduce hiding places like old pots and weeds

Keeping on top of them now prevents bigger infestations later in summer.

Flea Beetles

Flea beetles become particularly active during warm, dry spells in May. They are tiny black beetles that jump when disturbed and can cause serious damage to young brassica seedlings.

Rocket, radish, turnips, and mustard leaves are also common targets.

Signs to look for:

Tiny pinholes scattered across leaves
Seedlings looking shredded
Poor early growth

What to do:

Keep soil moist around plants
Cover seedlings with fleece or mesh
Transplant larger seedlings instead of direct sowing
Encourage quick growth with regular watering

Most mature plants recover well, but young seedlings can struggle badly.

Aphids (Greenfly and Blackfly)

As temperatures rise, aphid populations can explode very quickly. Soft young shoots are particularly attractive, especially on broad beans, fruit bushes, and ornamental flowers.

Signs to look for:

Clusters of insects on stems and shoot tips
Curled or distorted growth
Sticky honeydew on leaves
Ants climbing plants

What to do:

Pinch out broad bean tips once pods begin forming
Spray colonies off with water
Encourage ladybirds and hoverflies
Avoid overfeeding with nitrogen-rich fertilisers

A healthy allotment ecosystem usually helps keep aphids under control naturally.

Carrot Root Fly

May is also an important month to protect carrots from carrot root fly, especially once thinning begins. The smell released when thinning carrots attracts the flies.

Signs to look for:

Rusty tunnels in carrot roots
Wilting foliage
Poor root development

What to do:

Thin carrots in the evening
Avoid crushing foliage nearby
Use fine mesh barriers around crops
Sow thinly to reduce the need for thinning
Try companion planting with onions or spring onions

Prevention is much easier than dealing with damaged roots later.

Pigeons

While not technically pests in the insect sense, pigeons can be incredibly destructive on allotments during spring. Young brassicas and pea shoots are particularly vulnerable.

Signs to look for:

Leaves stripped down to stems
Pecking damage
Flattened plants

What to do:

Use netting securely
Install reflective tape or deterrents
Cover vulnerable crops early

Once birds discover a food source, they tend to keep returning.

Prevention Is Always Easier

The best defence against pests is a healthy, well-managed allotment. Strong plants are naturally more resilient and recover faster from damage.

Some simple preventative steps include:

Checking crops regularly
Rotating crops each year
Encouraging beneficial insects
Watering consistently
Avoiding overcrowding
Keeping weeds under control

And remember — not every insect is a problem. Ladybirds, lacewings, hoverflies, frogs, hedgehogs, and birds all help create a balanced ecosystem that naturally keeps many pests under control.

A few holes in leaves are simply part of allotment life, but catching problems early in May can make a huge difference to the success of your crops throughout the growing season.

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