slugs & snails
Runner beans are pretty problem free once they are well established. However, the young plants are a magnet for slugs and snails, so you really need to be on your guard. Starting them off indoors helps, as hopefully your windowsill or porch is pretty pest free, but once they are out in the garden, they are fair game.
If snails are a problem, get ahead of the game and do a thorough check under nearby pots and in cosy corners, it’s amazing how many hibernating snails you can find in the winter. Slugs are harder to find until they emerge with the warmer weather, so try some of our slug deterrents, and if all else fails a night-time slug hunt with secateurs in hand usually does the trick.
blackfly on runner beans
Black bean aphids or blackfly attack the tender shoots of many bean crops in the garden. The best approach is vigilance – keep checking the new growth for infestation of these tiny black bugs and squash them mercilessly. There is a theory that squashed aphids emit a pheromone that deter more adults from laying their eggs in the area. It certainly seems to attract their natural predators (ladybirds and lacewings) to finish off the job on your behalf.
Resist the use of pesticides, as if you allow the natural balance of predator and prey to emerge, your problem can be solved, and you therefore avoid killing off pollinators and other beneficial insects. If the infestation gets really bad SB invigorator is one of the safer pesticides to use as the fatty acids that coat and kill the aphids are less likely to affect the ladybird larvae.
runner bean rust
Runner bean rust is a fungal infection that appears in the shape of dark brown pustules on the underside of the leaves. It is prevalent in warm moist conditions, so try to avoid wetting the leaves when watering. Remove and destroy any affected leaves.
what is eating my runner bean leaves?
Most likely slugs or snails (see above).
why are my runner beans leaves turning yellow?
This could well be something called ‘Halo Blight’ which causes yellowing between the veins. It is caused by a bacterium and the best way to avoid is to keep well away from the leaves when watering your bean plants. Pick off any affected leaves and destroy, then destroy the affected plants and seed at the end of the season.
why are my runner bean flowers falling off?
The flowers will be falling off because they have not been setting (i.e. pollinated). See below for reasons why your runner beans aren’t setting.
why are my runner beans not setting?
There could be several reasons why you have flowers but no bean pods, particularly early on in the season. If it is still too windy and cold this can deter pollinating insects, so make sure you plant late enough and in a sheltered spot. There are some canny bumble bees that are frustrated by not being able to squeeze into the flower, so they ‘rob’ the plant by piercing the back of the flower to reach the nectar. Given that most years the beans are so plentiful you will be handing them to all your neighbours, you can afford to lose a few to the ingenious bees.
Later on in the summer if the weather is too hot and dry the flowers can drop off before they manage to set. Ensure you have plenty of organic matter in the soil to retain moisture, and water well at the roots in dry weather. It might also be worth testing the pH of your soil, as beans do not like it too acid (6.5 is about right).
why are my runner beans not germinating?
This is likely to be because the ground is still too cold. If they fail to germinate with a bit of indoor warmth, then the seed might have suffered from damp and begun to deteriorate. Always store your seeds in a dry box or tin in cool conditions.
