Tough Winter on Euonymus - Burned Leaves

This winter has been exceptionally tough on Euonymus foliage. I haven't seen a variety that was unscathed. Not to worry, winter burn and brown leaves will not be left on the shrubs for long.

Sections of this Euonymus, trained as a climber, has burned foliage dotted about.

This is a grouping of Sarcoxie Euonymus. Usually, its dark leafy green foliage is an attraction to plant as an evergreen hedge. Not this winter. Winter burn has caused the majority of leaves to fall off already, leaving this sample quite bare.

Euonymus are rather resilient shrubs and trailers. They will recover given time and adequate conditions. I'm actually quite pleased to see this damage happen. That may sound strange. As a gardener, I see Euonymus scale quite prevalent in the GTA and I believe it's because of our more recent, gentle winters. Scale insects nestle in and fixate tightly on remaining interior foliage and stems over winter and don't die off in large numbers due to protected warmer winter months. Now, I smile in gratitude - for more of these insects will have died off this winter, because of the harsher conditions.

This is Coloratus Euonymus - the ground cover variety. Even with adequate snow coverage, it too has signs of winter burn.

Healthy, soft buds are key to knowing the Euonymus will bounce back. Be sure to water your Euonymus in case we have a dry spring. Watering the plant will ensure the buds stay hydrated and will emerge as leaves during the growing season. In May, buds will unfurl to new leaves and the older burned leaves will eventually fall off. You can aid the process by shaking the bushes, or raking out the worst of the ground cover variety.

If Euonymus is grown as a climber and there's very little growth beneath, simply shake off dead foliage. If it is stubborn to fall off, then prune back to older buds.

Here, you can see healthy buds remain. Not to worry. They will refoliate the plant.

Once the leaves fall off the bush, examine the leaves on their underside. If you see white, flaky residue, it may be scale. Rake as many of the leaves as you can from beneath. It's likely they (not all do) have some overwintering eggs of Euonymus scale insects. Do NOT compost. Remove the leaves from your garden. Add compost or some triple mix to the soil below and be sure to water the plants if we have a dry spring. I caution adding synthetic fertilizers at this point, since scale insects favour stressed plants and love added nutrients. There are only so many healthy leaves to go around. You don't want scale to over-power the plant. For control of this insect, check out my post on Euonymus Scale.

If the leaves are remaining on a ground cover type, or you don't have patience to wait, you can cut back the stems on top, to reveal the green leaves that were protected beneath.Once the buds unfurl to new leaves, the plant should bounce back by June.

Euonymus Scale - Unaspis Euonymi

I don't think there's an Euonymus fortunei plant out there that hasn't been pestered by this insect.  Variegated, ground cover, topiary - they all can get it. Unfortunately, when folks first notice the plant covered with scale, it's at a point where it is so difficult to get rid of them.

Euonymus scale (unaspis euonymi) is a sap sucking insect that stays under the radar so to speak, until population levels peak - giving away their secret.  They begin to hide on rougher bark branches (towards the mid-inside section) of the plant, reaching newer growth once the new buds begin to break in late early May. Hiding underneath new leaves, they begin to develop multiple life cycles as they populate the plant. Males are white and the females (slightly larger) are grey. They have a juvenile crawler stage which are usually an orange-yellow colour.

Scale fixate themselves, sometimes several insects deep when infestations are bad. When the plant is completely covered, one can take a sharp tool and scrape quite a thick coating of scales off the euonymus branches. It's quite gross, really.


What to do when you see this:

1) Where you can, prune out and destroy infested branches or plants before the young crawlers emerge. Pruning is even beneficial just by removing adult scale numbers. Yet, if the plant has lost many leaves, this becomes difficult to manage.

2) Insecticides are virtually useless and ineffective, unless timed properly.  They are only useful when they are applied at the onset of infestation and at the overwintering adult and the crawler stages. This can be difficult to time.

3) Dormant oils: this is an effective method to coat and suffocate the female scales that are filled with eggs.  In order to work, the oils should be applied in early spring or late fall, when the plant is dormant and when temperatures are cooler.  Branches, stems and leaves must be thoroughly coated in order to suffocate the overwintering adults. Using oils can burn leaves if applied too late towards hot summer months, so be wise in applying.

4) Water.  I can't say enough about water. Watering the plant will help give the infested euonymus ample moisture to draw from, since the insects are sucking its sap.  But water is also a wonderful way to help dislodge the insects from the host. High pressured water from a simple garden hose can reduce numbers significantly, with a little coaxing from a brush or your hands rubbing over the stems as you spray. It's an arduous task, but one I've used myself during the summer months. There's nothing more dis-heartening than to see the scale bounce back in numbers after you've treated the euonymus bush earlier in the season. Spraying the bush with water every two weeks does significantly reduce the insects in number, giving the plant breathing room to take a rest from the infestation.  I've specifically sprayed after a good pouring rain. The scales soften their grip in rain and the hose pressure blows them off. You'll notice their floating bits in puddles around the bush once you've been thorough.

5) Don't bag or cover your euonymus over winter. I've seen it time and again, when folks think that euonymus need covering. What you're doing is limiting the harsher exposure of temperatures on the plant, protecting overwintering female scales. Frost kills a lot of insects, and bagging will just keep them cozy for spring to arrive. Also the bag doesn't allow snow, rain and the elements that help wash down the bush. Euonymus benefit from natural elements, just not salt!

Unfortunately, once you've had scale, it tends to be a recurring problem. No doubt your neighbour has these same bushes, with the same problems - so inevitably you'll have them visit again.

Prevention:

Euonymus scale love hot temperatures. Making sure your plants are not in hot areas is a preventative practice.  Don't plant them next to a brick wall. This is a fantastic breeding ground for euonymus scale. Watering your bushes in drought conditions makes the euonymus stronger and more apt to fend itself away from the a light insect attack. Spray with water occasionally during the summer months. The is a key preventative.

Regular pruning is necessary, to promote aeration, new healthy growth - bringing vigor back to the plant. Don't just sheer the plant into a ball or round shape. Get inside the bush; prune out dead or weak branching. Allow air and sunlight to reach into the crown of the plant. This allows euonymus to recover.

Don't plant multiples close together. Space the euonymus plants apart. That way, if one really gets scale bad, it's not going to jump to the next.

Watch:   keep your eye on especially euonymus leaves. Watch for yellowing areas, stickiness, loss of vigor and leaves falling in summer. These are all SIGNS that point to an attack.

Persistence works in the end.

Here are also other plants that can also be pestered by Euonymus scale as well:

• Buxus, boxwood;
• Celastrus scandens, bittersweet;
• Hedera helix, english ivy;
• Ilex, holly;
• Ligustrum, privet;
• Lonicera, honeysuckle;
• Pachysandra terminalis, Japanese Spurge (groundcover).

Be proactive. Always check every season for signs...