Broccoli disease ID - Ask Extension
We have Purple Sprouting Broc, a couple of varietie,s growing in a field since mid to late July and they have this disease damage showing up. It is,...
Knowledgebase
Broccoli disease ID #426690
Asked September 13, 2017, 9:02 PM EDT
We have Purple Sprouting Broc, a couple of varietie,s growing in a field since mid to late July and they have this disease damage showing up. It is, right now, localized to one area of the field. We have been doing overhead watering. There is a dry gray appearance on some leaves and the leaves affected are not on any one area (like lower or higher, new or old). There is consistent damage to the stem at the base with an area of rot and a hollow stem. The plant pulls apart and separates from the roots when pulled on. The field is well drained and was used for pasture for 6 years and this is the first row crop use since then. As of now other brassicas in the field show no signs of the damage. They broc has been under row cover for the most part.
Lane County Oregon
Expert Response
Hi: it's difficult to say exactly what the problem is looking at the pictures with your info. The rot of the lower stem is suggestive of a disease known as black leg but the leaf symptoms don't fit. Do you see any areas on the lower stem where there are tiny black dots? Black leg causes pretty severe stunting if you get simply lower stem rot from planting infected seed.
The fact that the affected plants are restricted to one area of the field has me curious about a root rot pathogen that moved into the stem. Does the root system that separates from the rotten lower stem look heathy, having the lighter color that is typical of healthy broccol roots?
Have you seen any cabbage maggot problems in the planting? The maggot feeding opens up plants to secondary pathogen problems, including rot of the lower stem.
Hi, I don't think it is black leg and I didn't find any black dots. The roots looked pretty normal and I haven't seen any cabbage maggots. I looked in the PNW and didn't see anything that really fit. One thing that I came across was Rhizoctonia solani Is it possible that it could present in this way?
It could be a Rhizoctonia problem, typically infected plants are stunted and part of the root system will look unhealthy. Affected stems will look constricted and the outer tissues on affected lower stems will slough off. That one stem picture looks a little different. The best way to confirm the problem would be a laboratory inspection via the OSU plant clinic.
