By Dave Zeldon and Ely Schweyer
This is a question we hear daily during the spring, summer and, especially, the fall. Unfortunately, many homeowners do not see any adverse changes occurring in their trees until they look dead, or nearly so.
You Might Not Need to Panic Yet
The discolouration and dropping of evergreen needles are a natural phenomenon and the main cause of needle loss in the wild. Evergreen needles, as the name implies, survive for a lengthy period, and in fact usually have a life span of five to seven years on healthy trees, however, they must be shed. The needles first start to die in the central and lower part of the tree, and this change progresses upward over time. You will see spruce trees naturally lose needles as they get older.
Age is an important factor here in causing needle loss and branch death, however, in landscape plantings of coniferous evergreen trees, pests and disease are likely the major cause of needle loss and dying branches. If there is a sudden fall of a very large number of brown needles and leaves, this signals to us that there is something drastically wrong!
This can happen as early as a year or two after a tree is planted. This is especially true in Haldimand and Eastern Norfolk County where heavy clay soils predominate. Spruce trees, for example, do not grow well on clay soils.
When You DO Need to Worry
Here are some of the more common problems, apart from natural aging that afflict spruce trees, the probable causes and ways of treating the problem.
☝️Unfortunately, these majestic trees, the most popular evergreen planted on our residential properties, incur many other pest and disease problems not dealt with here.
Symptom: Rusty brown needles that eventually fall.
Likely causes:
1. Internal fungus disease (called Cytospora or white blister canker). This creates cracks in the bark causing resin to drip and leave grey-white dripping streaks on the bark. The fungus also causes open wounds or blisters on tops of branches. These wounds can be greyish white or greyish blue in colour, eventually turning brown and black.
2. Feeding by spider mites which leave fine, poorly formed webs in the needles, especially near the ends of the twigs.
Best treatments:
1. Properly aerate and fertilize tree out to a distance of half its height in all directions, where possible.
2. Pressure wash thoroughly once a month with water only, all needles and branches as high as possible on the tree. Water pressure dislodges spider mites.
Symptom: Chewed up ends of twigs in June.
Likely cause:
Spruce bud worms which develop in the needle cluster that arises from a bud.
Best treatment:
Spray the biological pesticide, BTK (eg. Dipel), onto the entire tree when feeding is first noticed in early spring, to kill the young caterpillars.
Symptom: Black sooty mold covering twigs and needles.
Likely causes:
1. Spruce bud scales, ball-shaped insects, initially light brown in colour but eventually turning black. Often two to five scale balls cluster in one location on the twig; honey dew excretions from scales become infected with sooty mold.
2. An overhanging shade tree such as oak, maple or elm may have heavily infested leaves with aphids whose honey dew secretions become infected with sooty mold.
Best treatment:
1. Pressure wash tree using water only to dislodge young scales (called nymphs) in May and early June while they are in the crawling stage. Scale nymphs fall to the ground where they cease to be a threat to the tree.
2. Spray shade tree in early spring with insecticidal soap to control aphids. The problems of other coniferous evergreens such as pines, firs, cedars and junipers can usually be treated with correct diagnosis, though some diseases are lethal.
We hope these help you troubleshoot common issues often found in evergreen trees! For more information - and evergreens – visit Eising Greenhouse and Garden Centre! 🌲
Figures.
By Dave Zeldon and Ely Schweyer
Now that we’ve brought our plants inside the house to over-winter, we begin to notice those slender, dark gray flies (0.2- 0.4 cm long) flitting about atop the pot soil. Yuck!
These insects are known as fungus gnats (Bradysia sp.). Whereas they are considered only to be a minor nuisance in house plants, due to their sheer numbers hovering around an attractive plant, they can certainly take away from its appeal. Below is a bit about these pests and some basic control measures.
How Do Fungus Gnats Affect Your Plant?
Other than their swarming presence, fungus gnats are not a direct threat to your plant, but an indirect threat. As their name implies, they are concerned with snacking on the fungi mycelium living in your plants’ soil. (Yes, it’s there and it’s a good thing!) However, these little flies can transfer disease between plants, making them nuisance pests.
A Quick Look at Their Life Cycle:
Adults may lay 300 eggs at a time, which hatch a week later into tiny, threadlike larvae. The larvae feed upon organic matter in the potting soil. After two weeks, they pupate into winged adults, that have no trouble annoying you to no end.
Basic Control Measures:
- The fastest and easiest method of control is to catch the flying adults with yellow sticky cards. The large cards can be cut into little strips and mounted onto little wooden splints (popsicle sticks) then placed around the base of the plant out of the line of sight.
- Water your potted plant from the bottom (sub-irrigation) by adding water to the saucer it is sitting in. This will keep the soil surface dry, making it uninhabitable for the hatching insect larvae. If the surface soil is already very wet, try placing a few potato discs or slices on the surface of the soil. This will attract the larvae as they migrate to the potato to feed. Simply replace the discs every three to four days with fresh slices to eliminate the next generation of adults.
- If you have a large number of plants afflicted as in a greenhouse situation, an application of predatory nematodes (Steinernema feltiae) as a soil drench is suggested. Nematodes will attack the fungus gnat larvae in the soil which will in turn lead to more nematodes being produced.
Good Bugs Are Working at Eising Greenhouse and Garden Centre!
Here at Eising’s Greenhouse and Garden Centre, we practice what as known as I.P.M. or Integrated Pest Management. Since we try to create a perfect environment for our plants, we also, unintentionally create perfect conditions for their related pests. To keep the pests at bay, we institute series of steps:
1 - Cultural Controls: We select only the healthiest of plant material to sell and keep them healthy through proper fertilization and growing conditions. We’ve learned that insects are attracted to stressed-out plants!
2 - Physical Controls: We are constantly walking through our plant aisles checking for insect and disease presence and removing the affected plants. Also a clean growing area means there is less chance of pest populations building up on alternate host plants such as weeds.
3 - Biological Controls: At the beginning of the growing season, even before there is any evidence of pest problems, we introduce naturally occurring predators into the growing areas. This is to be at the ready for when the pests do arrive!
In our arsenal we have a series of tiny parasitic wasps, microscopic wire-worms called nematodes, predatory mites as well as bacterial inoculants. So therefore, we cannot spray any chemical insecticides as they will hurt our very valuable biological cache!
Did you ever imagine all the behind-the-scenes work that goes into your plant purchases from Eising's to make them the best value around?
For more information – and bug products - visit Eising Greenhouse and Garden Centre soon! 🪰