Pests & Diseases

Organic solutions for common allotment pests

For many us sharing the allotments with wildlife is one of the major joys of being a plotholder - but whilst we welcome them on to our plots, we don’t always want to share our crops with them! Chemical methods of pest control are becoming less popular and with good reason: they pose a serious threat to the environment, wildlife and humans.

Harmless as they seem, the popular blue slug pellets containing metaldehyde not only kill slugs but can also kill non-target species such as birds and amphibians too if they eat a slug that has been poisoned. They can also cause harm to toads and frogs via pellet residue in the soil. The good news is that there are a wealth of organic pest control methods available which are much better for us, our crops and wildlife whilst being just as effective.

Here is a list of 4 common pests found on the allotment and some environmentally friendly, organic ways of tackling them:

Cabbage White Butterfly larvae damage.jpg

SLUGS

Do Dig! Reduce slug populations by working the soil frequently to expose eggs, young and adult slugs to predators and weather.
Good hygiene around your plot helps - remove and check any hiding places for slugs such as black polythene and pots.
Point water your plant using a spout not a spray rose. If the surface soil is kept dry it makes slugs' life more difficult.
After wet days and/or after planting new plants, check for slugs in the evening and dispose of any you find.
Put a pond in - even a tiny pond can attract toads & frogs, who in turn work hard to control your slug population for you. Similarly leave enough natural shelter and you may be lucky enough to get a hedgehog on your plot to hoover the slugs up.
Start crops off in pots or modules at home and plant them out once they’re more established, making them slightly less tempting to slugs than young seedlings.
Physical barriers to keep the slugs off your seedlings; copper tape, eggshells, coffee grounds around the base of your plant or frame have been cited to work. Also beer traps sunken into the ground lure slugs in, though the traps need refreshing regularly.
Slug Gone. Not a cheap option but an organic wool based mulch called Slug Gone sprinkled around the base of your seedlings and watered in, is brilliant not only at keeping the slugs away but also rots down to add nutrients to the soil.

APHIDS

...including blackfly found on your broad beans / runner beans and greenfly which can show up on lettuces, potatoes, etc.

Bug pals encourage natural aphid predators on your plot such as ladybirds and hoverflies by keeping the plants they love such as nettles and attract them by sowing annual flowers such as French marigolds and nasturtium.
Jets of water can work well to blast aphid infestations off your broad beans or runners when you’re giving the plot a water.
Squashing them by hand, if you’re not too squeamish, can be an effective way to control small populations.
Pinching out the tips on your broad beans and runner beans once they start flowering will help deter infestations as they are particularly attracted to the sweet tips.
Spraying your crops with water mixed with garlic cloves and a drop of hand soap is one home made remedy that can work well to control small infestations.

Large Cabbage White Butterfly Caterpillars

The beautiful cabbage white butterfly can’t resist laying its eggs on your cabbages, cauliflower, sprouts and broccoli, nearly any brassica in fact which in turn can become overwhelmed and consumed by hungry caterpillars!

Encourage birds that eat the caterpillars to your plot by keeping / planting features such as trees and hedges which provide food and shelter for them. My favourite geek fact is that a pair of blue tits can eat 10000 caterpillars and one million aphids in 1 year. Impressive hey?!
Covering your crops with fine mesh insect net (such as Enviromesh) or fleece as soon as you plant them and leaving it in place the whole time can help prevent the adults laying eggs on your crops

Carrot Fly

A small black fly whose larvae feed on the roots of carrots, parsnips and others making them inedible and causing secondary rot.

Surrounding your crops with a barrier of fine netting or fleece to approx 40cm high will stop these low flyers from reaching crops
Use resistant seed - cultivars such as Carrot 'Resistafly’ or ‘Flyaway’ show greater resistance to the pest, so choose these when buying your seed
Avoid crushing the carrot foliage when weeding and thinning the seedlings, as the smell can attract the carrot fly. Thin out seedlings after watering when the smell is masked or in early evening when the fly is less active.

Rebecca, Plot 39W