What Is Eating My New Runner Bean Plants?

Slugs

• Slugs are a persistent pest when it comes to runner beans. These shell-less snails love to eat the roots, pods, leaves and stems of your runner bean plants, not leaving much of a plant left, if at all. Slugs are slimy little legless creatures often varying in shades of green. They can vary in size from a few centimeters to 6 inches and bigger. A slug problem is usually easy to identify for two reasons. First, slugs are slow and you'll probably see them if they're in your garden, and second, they leave a trail of visible shiny residue behind that will lead you to their exact location.

Blackfly

• The blackfly, an aphid, feeds on the shoots of runner bean plants. According to Everything-Runnerbean.com, a serious infestation of blackflies can severely stunt a plant's growth. Blackflies are little black bugs about 1 to 2 cm long. Oftentimes, simply spraying the aphids with a water hose is enough to knock them off your runner bean plants.

Bean Seed Fly

• The bean seed fly often attacks poorly rotated crops in damp and wet conditions. According to Everything-Runnerbean.com, bean seed fly maggots are actually the pest here, not the flies themselves. The maggots eat and destroy the plant's seed, causing the plant to wither and eventually die. Unfortunately, once you notice this pest, it's usually too late. Scrap the infested bean plants and remember to rotate your crop to avoid this crop destroyer in the future.

Misdiagnosis

• The untrained eye of a novice gardener can easily mistake some plant diseases and ailments for pests. After all, many diseases cause the plant to be eaten away by bacteria or fungus. Seedborn diseases, such as halo blight and bean anthracnose, are incurable, meaning you'll simply have to replace infected plants. Search the plants over for the pests mentioned in this guide; if you never see any, but your plants keep getting worse, then chances are your plant is diseased.

Solutions

• According to GardenAction.co.uk, several beneficial insects eat blackflies, such as ladybirds and hoverflies. You can attract these by planting marigolds near your runner bean crops. The same site suggests using nematodes to control your slug population. Nematodes are microscopic organisms that are harmless to humans and plants but deadly to slugs. If these methods fail you can always try chemical pest control. (Verify the chemicals you use on your runner beans are totally safe for crop consumption.)