The first step in pest control is choosing disease-resistant plants. Here are some tactics for when infection strikes, from killing aphids to stopping common fungus.
1. Aphids, white flies and spider mites
- Aphids, mealy-bugs, leaf hoppers, cottony scale and white flies love to eat leaves and needles.
- Infested needles and shoot tips become sticky or deformed when plagued with these bugs, and may show sooty mould. Pests could also be visible.
- Spray with insecticidal soap to kill them. Use soapy water to remove sooty mould.
- Foliage with spider mites turns yellow, then brown. It may have a purplish tinge.
- To get rid of little mites, spray forcefully with water, especially undersides. Also apply insecticidal soap every 5 days.
2. Borers and caterpillars
- Shoots of trees with borers will wilt, become crooked or stunted. They then die rather quickly.
- To destroy borers, prune out the infected shoots and destroy.
- Caterpillars, sawfly larvae, gall midges all leave eaten needles, entirely or in part.
- Apply Bacillus thuringiensis for caterpillars, insecticidal soap or neem for other pests.
3. Canker fungus
- Cytospora canker fungus causes needles to turn yellow and fall. White resin may appear on the on trunk and branches.
- Prune the infected branches. In spring, spray 3 times, every 10 days, with copper-based fungicide.
4. Needle cat fungus
- Needles with this fungus turn yellow in late summer, brown in winter, and eventually drop. It often starts at base and moves up.
- Needle cast is common in spruce and pines.
- To help your tree fend it off, spray with a Bordeaux mixture. Spray in summer, 3 times, every 21 days.
5. Rust fungus
- Several different rusts attack conifers.
- Infected trees will have dead branches in the crown, white resin on the trunk or yellow patches on its needles.
- To cure, prune out infected branches and spray with wettable sulphur.
6. Twig blight fungus
- The telltale sign of this fungus us that shoot tips yellow in fall. Needles will also hang on without falling and black spots can appear on shoots.
- Prune infected shoots, and spray 3 times with copper fungicide after the needles fall.
If buying a disease-resistant tree doesn’t work, you can try these solutions. They’ll mostly be useful for young trees, but if a tree suffers problems year after year, it’s better to cut it down and replace it with a different species.