Pests or Not? Ants on Broad Beans

Posted on 19. May, 2010 by Tracey in Pests

During May when broad beans are flowering you may find ants running up and down the stems feeding from small dark black spots. These dark black spots are clusters of tiny blackfly (or black bean aphids) and the ants will be farming them and eating their honey dew secretions.

If you have ants, you usually will have black fly, check at the tip of the plant, under leaves or where the leaf meets the stem for clusters of black insects, these are black fly.

Are ants harming the plants?
No but if they are farming blackfly, your plants may be at risk from disease especially if the blackfly spread to other plants.

Blackfly on Broad Beans

How do I get rid of the ants?

If you get rid of the blackfly population, the ants will move elsewhere,
Try planting lavender or curry plants nearby to deter the ants,
A hosepipe will spray most of the ants off the plant, but they may return,
I leave the ants alone, check the plant regularly for black fly clusters, then squish them.

Are black fly harming the plants?
Yes, they drink the sap out the plant, if the black fly population is large this could lead to loss of nutrients which stunts the growth of the plant. In severe circumstances the plant could die. Black fly can also transmit diseases which can spread to other plants in the area.

Methods to remove black fly from broad beans

Broad Bean Tip

Try growing nasturtiums or poached egg plants nearby as black fly love them,
Homemade solution of very diluted washing up liquid to spray on the black fly,
Introduce ladybirds and lacewings to the area by buying them or putting up a nest box,
Remove the broad bean tips (and any black fly) by pinching out the cluster of leaves together at the top of the plant as soon as your first beans at the base of the stem start growing,
Squish any further black fly between your fingers (wearing gloves).

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