Not all leaves are affected. I don’t know if this is normal or abnormal. I juice my greens so I need to find out what this is and whether I should just be ripping off these leaves and not composting them.
I juice my greens, so it’s important that I figure this out.
I grow in above ground garden boxes, and I have a timed irrigation system, which I turn off if rain is coming. Zone 6. Sunny all day. Soil is loam.
Thanks for any help you can give me on this
Thank you for contacting the Toronto Master Gardeners.
Collards are in the brassica family, which is affected by a very large number of pests and diseases. Although many types of insects lay their eggs on the underside of the leaves of brassicas, it’s very hard to tell from the photo if these are insect eggs.
Have you seen any other symptoms that might help you narrow in on the cause, such as yellowing or leaf damage (e.g. holes in the leaves, noting their specific placement, such as at the leaf margins or veins), something eating the tissues between the leaf walls, or perhaps damage at the growing point of the plants? Have you inspected the plants at different times of day/night to see what creatures might be visiting them? This could also simply be scaring that develops if the leaf edges are rubbing along the sides of your raised garden boxes or against other structures.
A few pest culprits that may be at work are cabbage aphids (Brevicoryne brassicaea), a common sucking insect, although they lay their eggs later in the fall for overwintering, and are a distinctive grey-green colour with a waxy looking coat, and would be relatively easy to spot on your plants. Cabbage looper (Trichoplusia ni) is another common pest that can cause quite a lot of damage, but again, their eggs and caterpillars are distinctive and relatively easy to identify.
Take note of any other symptoms and signs of pests as noted above, and if don’t spot any, perhaps this is just natural scarring or minor damage from the plant rubbing on nearby structures or other plants. If you do see other symptoms of an insect present, insecticidal soaps are helpful in combatting many kinds of insect pests and are safe for vegetable crops that you plan to consume. They are effective immediately and can be used every 7 to 10 days to control many insects.
If you find a larval pest that is consuming your plants, you can use a biological pesticide called Bacillus thurengiensis, which comes in several strains and is available at garden centres across the GTA. It’s usually sold in a small bottle as a concentrate, so follow the instructions carefully.
Also if you spot larval insects, you could employ lightweight row covers to protect your plants from flying insects that may be laying eggs on your food crops.
Finally, if you are in zone 6 you are outside the Toronto Master Gardener’s advice area. You likely have a local Master Gardener chapter. You can review the Master Gardeners of Ontario group list to get in touch with a group representing your region.
More resources that may be helpful to you:
Kale Insects, Toronto Master Gardeners
Aphid, Cabbage, UMass Extension Vegetable Program
Collard Greens, Plant Village