We only received one of the photos (the file name with 2832), and unfortunately it's hard to diagnose the symptoms pictured. From your description, though, it sounds like one culprit might be voles. Are any surface tunnels/runways visible, such as soft spots or mounded-up soil?

As mentioned in our Growing Broccoli page, it can be grown in autumn as well (starting around late July or early August), and while that crop maturity might take slightly longer than in spring, the plants might be less likely to bolt (flower) while producing better yields. Perhaps recent cooler temperatures stimulated flowering.

We do not recommend the use of insecticides unless a specific pest has been seen causing damage and identified. We are happy to help ID a suspected pest if you want to share photos next time you find one. Pesticides used without being able to target the right insect risk harming pollinators, beneficial insects (that can prey on the pests), and other organisms. Often, they are not needed and other methods (like using row covers and insect mesh) can exclude pest insects without a need to spray. The worm-like organisms you saw might have been millipedes (they consume dying vegetation, like rotting roots, damaged stems, or cut-off leaves), but it's hard to say without photos. Nematodes are hard to see without magnification, but sometimes they are barely visible. They must stay wet, so are unlikely to be seen in soil that isn't freshly moist, and some will be inside the plant and not visible loose in the soil.

The soil in the background of the photo looks poor, in the sense of not having much organic matter [OM] content. Did the soil lab tests indicate an OM level that was low, below 2%? If so, adding a yearly top-dressing of an inch of compost can help boost OM levels over time, which will help nourish plant roots and the beneficial microbes in the soil that keep them healthy.

Miri

Hi Miri, Thank you for your quick and thorough response, it is greatly appreciated! 

Perhaps I should first clarify my background so you know my perspective on this matter a bit better. I have a degree in Landscape Horticulture from NC State and have been in landscaping, lawn care, and pest control for over 30 years. I am currently licensed in 7 categories in Maryland  for commercial applicator's license and Professional Fertilizer Applicator's license as well. That being said, I certainly don't  know it all which is why I'm seeking your help. 

My target pest on the cabbage/broccoli were cabbage loopers and cut worms which were active and have been a perpetual problem annually. I totally agree with you on protecting pollinators and choose method, product, and timing to limit (or eliminate) any damage to beneficial insects. Chemical applications are always a last resort in my work or home. I have tried floating row covers several times and find them impractical in many circumstances but agree they may be a viable option in some cases.

Specifically regarding my cole plants issue, I do grow two crops of of cabbage and broccoli per year, spring and fall along with collards and kale in the fall/winter. I certainly can see why you suggested voles as a potential culprit but it is definitely not voles. Unfortunately, I could not locate my most recent soil test to verify % O.M. but my soil is not as bad as it appears in the photo and I regularly till in cover crop/plant material to provide O.M. 

One thing I did not consider is some type of phytophtera/root rot, but drainage is generally good and any plants in the wetter spots of the garden fare no worse. Attached are a few more photos in which hopefully you can see where the below ground vascular tissue is damaged/sloughing off of the stem. The one photo shows the once-healthy fibrous roots are now dead and another shows the plant trying to start new roots above the damaged area on the stem. 

Again, I really appreciate the information you have provided but don't feel problem has been identified yet. It may well be a cultural practice of some type I am doing incorrectly. Any additional information you can provide would be greatly appreciated because at this point it's got me stumped! Thank you so much!!

Thank you for the additional background information and photos. Our plant pathologist does not see an indication of a problem except for what you suspect might be root rot. We agree it looks like there might be sloughing-off of the outer root layer, but the photo isn't quite in focus for us to tell. Fine root core filaments exposed by this process might look like nematodes, though of course they would not be moving whereas nematodes would. (He also says that you would not likely be seeing any nematodes in this situation; they are too small and would not be "free-swimming" in the soil where they would be visible.)

We do not know why some plants would be succumbing to any of the various root rot pathogens (Phytophthora, Pythium, Rhizoctonia, Thielaviopsis, etc.) only in this part of the garden if a nearby area tends to stay wetter and the broccoli/cabbage is unharmed there. An acidic pH can play a role in suppressing these kinds of pathogens, but your pH level seems suitable as-is. Damping-off (Pythium) might be occurring, though that tends to happen indoors before transplanting, so we'd not expect it at this stage of growth. Black leg can girdle stems, but we can't see enough clear detail in the photos (and they don't show foliage) to determine if the characteristic speckling is happening. Wirestem can also girdle the stem, though as noted in the linked page above, it is more prevalent in warm conditions for fall brassica crops rather than cool soil.

Perhaps the plants are struggling in the potting mix while they are still indoors, predisposing them to infection once  put outside, since some potting mediums have been reformulated by the manufacturer over the years. (They may be changing the proportion of ingredients if they are trying to reduce their dependency on peat moss. For example, some are using more "forest products" than they used to.) While we would think that a compromised root system from the start would not allow for the seedlings to look as good as you describe when ready to go outside, maybe the more pampered conditions of indoor growth is masking symptoms of stress that can't be avoided once they go outside and a greater demand is placed on a root system that might be in poor shape.

There is no fungicide we'd recommend for this case if it is a root rot, so all we can advise is either trying a new planting site or raising the soil grade a bit (into a raised bed or deeper bed). Do you happen to use the same containers for seedlings each time you start a crop indoors? If so, are they being sterilized between crops?

It may be hard to narrow-down the potential pathogens further, but you can share a photo or two of the entire planting site if you think it will help us determine a causal agent.

Miri