Elisabeth C. Miller Library logo Miller Library Home UW Botanic Gardens Home UW Botanic Gardens Home book graphic

3501 NE 41st Street, Seattle, WA 98195 | (206) 543 0415 | Open Monday 9-8; Tuesday - Friday 9-5; Saturday 9-3

Gardening Answers Knowledgebase


Knowledgebase record #790


PAL Question 

I have small ants on my fava beans and it appears that some of the young pods are blackening. Do ants eat fava beans? Is there anything I can do this year, or should I just start over next time in a different location?

Answer 

The ants may be visiting the extrafloral nectaries of your fava bean plants! (see this photo of just this activity)

Apparently, some insects are attracted to the nectar of Vicia faba, as this Oregon State University Extension page describes:
"Many beneficial insects, including predatory wasps and lady beetles, are attracted to the nectar of flowering fava bean.
Fava bean also has extrafloral nectaries on its stipules, the leaf-like structures at the base of the leaf petioles. Extrafloral nectar is available to short-tongued insects that do not have access to the nectar of the legume flowers. Both beneficial and pest insects (e.g., lygus bug) feed on extrafloral nectar.
Fava bean is susceptible to aphid damage, especially from the bean aphid. Although aphids usually do not affect fava bean's utility as a cover crop, they can cause considerable damage to the seed. Broadbean weevils also can reduce seed yields."

Here is similar information, from Golden Gate Gardener.

It's possible that the blackening is from aphid honeydew, or perhaps it could be chocolate spot, which is a fungal disease (Botrytis fabae). Here is more about this, from the Royal Horticultural Society.

Practicing crop rotation might be beneficial with your favas as it is with other edible plants. Below is additional information on vegetable crop rotation.
Washington State University Extension: Vegetable Garden Evaluation and Planning Ahead
Penn State: Crop Rotation

To check your favas for botrytis or other diseases, take samples to a Master Gardener Clinic for diagnosis.

Keywords crop rotation, Vicia faba, Vegetables--Diseases and pests
Season All Season
Date 2010-06-04

Need an answer to your gardening question? Ask us directly!

Browse keywords or Search Again:

Keyword Search

We are continually adding new questions, so be sure to keep coming back.

June 24 2013 13:17:10