I am trying to overwinter broccoli outdoors, completely exposed with no...

Asked February 9, 2015, 11:40 AM EST

I am trying to overwinter broccoli outdoors, completely exposed with no covers, with some success (the plants are still alive and somewhat green in February). I had a nusiance level problem with whiteflies last fall but it was late enough I thought winter would just kill them off. This hasn't happened. I have live whiteflies on my broccoli and while numbers are below damage thresholds I am very concerned they will survive the winter and become a problem in spring and summer. I do not have any on my few houseplants inside and there are no greenhouses nearby where they might have come from so I think they really are surviving our normally cold winter. Is this sufficiently unusual I should report it and save samples? I will take pictures and send one in a separate message but I am sure these are whiteflies. I cannot identify the species though.

Prince George's County Maryland

7 Responses

We have had reports of white flies appearing very early in spring and suspicions that they have somehow survived the winter. We'd recommend that you spray the broccoli white flies with a horticultural oil or soap or possibly Spinosad. Read the label closely for temperature limits for spraying.

You do not need to report these white flies, however we're curious how your broccoli will do by spring. We think you may get edible stalk and leaves but not heads. If you can send us a digital photo of how it looks, we'd like to see it.

ECN

attached is an image of the broccoli plant and two images of the whiteflies. The broccoli may be in trouble if predicted cold 2/15 verifies. The brussels sprouts above it were planted too late and will not produce. I have other brussels sprouts in my rental garden off Cherry Hill Road which are ready but should hold all winter until I can use them. I also have broccoli there under heavy opaque blankets (currently uncovered) and expect the heads of these to survive. Quality is questionable. I overall think there is underexploited potential for winter gardening in the Mid Atlantic but have only had access to winter land for three years and am still working out techniques.

I forgot to add that I will be spraying with insecticidal soap, oil, or NEEM as soon as temperatures increase. After problems with broad mites this fall I finally added these to what had been a pesticide free garden shelf. I can deal with the whiteflies at this level of infestation but was very concerned that they were overwintering.

Insecticidal soap and oil are organic and extremely safe to use. Neem is also considered safe for organic gardeners.

Your broccoli looks terrific, considering the cold temperatures we have already had. If you're concerned about the upcoming low temps, cover briefly with row cover, blanket, etc.

Since you are concerned about overwintering, be sure to knock out the whiteflies on a nice day.

ECN

Just an update. I do not know if the broccoli survived the Feb 15 and 19-20 cold outbreaks. It is still green but the central florets are bleached. I expected this with 7F with strong winds on Sunday 2/15 and 3F on Friday 2/20. Outdoor temperatures went above freezing today 2/22. I checked for whiteflies on a leaf. There were five. Upon warming (indoors) it looked like four were dead but one had survived and began moving across the leaf. So I suspect even with this cold, a few survived. I will check my remaining Brussels Sprouts when weather improves. I've just sent this to report that a small fraction survived the three arctic outbreaks on 2/13, 2/15 and 2/19-20. I did find a large fraction of survivors on my brussels sprouts 2/14 but I've not been out there since to determine if any survived the other two cold outbreaks. I will use horticultural oil or neem when temperatures get above 50F at night or 60F for a large fraction of the day. This is not a question, just a followup

I went to my rental garden and checked the brussels sprouts on March 8. THey were alive but not of edible quality with the centers of the sprouts killed. I then checked under the remaining green leaves. There were whiteflies and one flew off while I was looking. So they definitely survived the winter in both my backyard (where the pictures were taken) and my colder stream valley rental garden location across from Seven Springs on Cherry Hill Road. There were only a few and I don't expect problems controlling them. But I do believe their survival through a winter severe for Maryland, should be documented somewhere. The key factor was that they had a green and living host to feed and shelter on. Brassicas (kale and brussels sprouts) survive normal winters in Central Maryland and will serve as an overwintering host. So should I try to get this documented? By the way the photographed broccoli plant which was looking terrific, finally exceeded its tolerances and is severely damaged. This was expected. I had opaque row covers (old blankets) in my colder Seven Springs location and broccoli under these looks surprisingly good. I do not think though that the whiteflies hid there. and flew out later because I don't have any under the row covers. I did not use row covers at my home except for on some lettuce which has no whiteflies at all.

Thank you. This is interesting information and we will let our entomologist know about it.
mh