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Plant Answer Line Question

Keywords: Beans--Diseases and pests

I have planted green beans three times because I have an annual problem of the leaves either being completely chopped off or they appear lacy and nearly gone. I have seen slug slime, so that may be some of the problem, but what does the lacy leaf indicate? I also have a lot of "potato bugs" or "sow bugs," could that be the problem?


According to The Organic Gardener's Handbook of Natural Insect and Disease Control edited by Barbara Ellis (Rodale, 1996), lacy leaves on your bean plants might be the work of Mexican bean beetles. Parasitic wasps (Pediobius foveolatus) can be used to control the Mexican bean beetle. As a last resort, you can spray or dust your plants with pyrethrin. See links here:

From the Connecticut Agricultural Experiment Station

From the University of California

Large holes in the leaves may be caused by other beetles as well, such as the cucumber beetle, which can be managed by protecting your plants with row cover like Reemay. If damage is severe, you can use pyrethrin or neem spray.

Small holes in the leaves may be the work of flea beetles, and the management is the same as above.

The chopping off at ground level sounds like it could be the slugs eating shoots as they emerge, or climbing up the plant and eating it down to the ground. It could also be the result of cutworms. Look for these at dusk, and look during the day at or just below the soil surface. I manage these pests by looking for them frequently, and squishing them or cutting them in half with my pruning shears.

I had never heard of sow or pill or potato bugs (isopods) being a vegetable pest, but apparently they do have that potential if the population is large enough. See the discussion among gardeners on Gardenweb.

You might try fooling the pests by planting your beans in a different location, especially a raised bed.

Date 2018-05-04
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Plant Answer Line Question

Keywords: Beans--Diseases and pests

I have grown runner beans in the center of England for several years, with good crops and healthy plants, but this year my plants have some sort of disease. The leaves have brown spots which seem to spread along the leaf veins and then over the whole leaf. Some plants are still producing healthy beans, but on some plants the beans have shrivelled and turned yellow. I don't know if these are the same plants with the worst leaf problems as the plants are tangled together too much. I have looked at various websites, but am not sure that any diseases shown correctly match my problem. I would be very grateful if you have any idea as to what it is and how to deal with it.


While I cannot diagnose the problem remotely, your description does sound quite a bit like anthracnose, which is a fungal disease. According to The Organic Gardener's Handbook of Natural Insect and Disease Control by Barbara Ellis (Rodale Press, 1996), this disease thrives in wet, humid conditions. You would see leaves with dark streaks, and black petioles and veins on the underside of the leaves. If this is indeed the problem, plants may be sprayed with sulfur, or you can seek out resistant cultivars next time around ('Espada,' 'Marbel,' Morgane,' and 'Rocdor' are a few).

On the other hand, the yellowing of the seed pods sounds more like bacterial blight, also encouraged by warm, damp weather. If your plants are not forming any new pods, remove and destroy them. Next time you plant, be sure there is adequate space between plants, and perhaps rotating the crop to a different location might help.

Just to give you some basis of comparison, here are links to sites with information about diseases affecting beans:

Cornell University Vegetable MD Online

University of California, Davis Integrated Pest Management

Royal Horticultural Society lists several problems affecting runner beans. There is a fungal disease of broad beans called chocolate spot which sounds a little like what you describe.

Date 2018-06-22
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May 31 2018 13:14:08