Broccoli, Cabbage and Kale are among our most important crops at Terra Firma, and we grow them from October through March.  Cauliflower and Brussels Sprouts are very closely related to those crops, but we grow very little of the first and none at all of the second.  Why? Because of aphids.
Aphids like brassicas in all forms, and we spend quite a bit of time controlling them as best as possible. But once they get into the nooks and crannies of a head of broccoli or cauliflower, it’s impossible to reach them with the natural, oil-based sprays we use to desiccate them.
Conventional farmers use “systemic” insecticides that are absorbed into the plants through their leaves or roots and spread through every part of their tissue — including the part that humans eat.  These chemicals provide “total control” of aphids because the minute they begin to feed on the plant, they are also consuming the pesticide.
We have fewer problems with aphids in broccoli than in cauliflower simply because it matures faster, giving the bugs less time to infest the plant:  two months compared to 3 or even 4 months.  (Brussel Sprouts take 4-5 months, which is why we don’t grow them.) But you probably have still found aphids in your TFF broccoli from time to time when you are chopping it up.
Cabbage grows very differently from broccoli and cauliflower, making it much harder for the aphids to infest the actual heads once they get to be a certain size.  It’s also easier for our harvest crew to see the infested heads and leave them in the field.  The same is true for kale, which we harvest one leaf at a time.
If we have extra room after allotting for all our Broccoli, Cabbage and Kale fields in each year’s crop plan, I will plant a small amount of Cauliflower.  Last year the crop did well, with few pests problems, so I grew a little more this year.  Had it succeeded, we would have been harvesting cauliflower since New Year’s.  Instead, the first two plantings were so completely infested with aphids we never harvested a single head. It was a total loss.
Aphids, like humans, love certain weather: dry and sunny with temperatures between 65 and 80 degrees. Given this weather for more than a few days, they reproduce disturbingly quickly.  Rain and cold slows them down, but doesn’t kill them.
This fall and winter, like many of the last ten years, has seen been well above historical average temperatures.  Fall of 2019 in particular was warm and dry until Thanksgiving, providing the aphids an extra long period to get established and breed in our brassica fields.  Even though it did get cold in December and part of January, the populations were already established by then.  We’ve seen more aphids in our broccoli and kale this winter too.
We appreciate your understanding of the challenges climate change adds to our efforts to bring your the best selection and quality of winter produce we possibly can. It makes me sad that we can’t reliably grow bug-free cauliflower for your boxes, but it’s definitely not from lack of trying.