In this post, I’m going to talk about a common problem that many Weigela lovers face: Weigela leaves turning brown.
Weigela is a splendid shrub that delights the senses with its vibrant and aromatic flowers in spring and summer.
You're reading: Weigela Leaves Turning Brown: 7 Reasons Why and Remedies
But sometimes, its foliage may become brown and withered, diminishing its charm and vitality.
What are the reasons behind this issue and how can you resolve it? Keep reading to discover.
1. Frost
One of the most common issues that Weigelia faces is frost damage.
When winter temperatures drop as low as 0°F, the tender tips of the branches can suffer from frostbite and die back.
Although this does not permanently harm the shrub, it can affect its appearance.
Remedy
To improve the look of the shrub in spring, it’s best to clip off the dead branch tips before bloom time.
2. Scale
Scale insects are another problem that Weigela may encounter. These insects feed on the plant’s tissues while protected by rounded, waxy shells.
The scale shells can appear as small bumps or blister-like outgrowths on the stems and leaves of Weigelia.
The first sign of a scale infestation is usually discoloration of the upper leaf surfaces, followed by leaf drop, reduced growth, and stunted shrubs.
Heavy infestations can even lead to the death of the shrubs.
Some scale species secrete honeydew, which attracts ants and encourages the growth of sooty molds.
Remedy
To handle mild scale infestations, you can simply scrape off the bumps with a fingernail or use a cotton swab dipped in rubbing alcohol.
For heavy infestations, spraying the shrub foliage and stems with a light horticultural oil can effectively smother the scale insects and their eggs.
Avoid over-fertilizing, as it can encourage lush growth that is more susceptible to scale attack. Using a slow-release nitrogen fertilizer can help prevent this issue.
3. Four-lined Plant Bug
If you notice irregular bronze or tan spots on the upper leaves of your Weigela shrub, it may be due to an infestation of four-lined plant bugs.
These bugs are yellowish-green as adults and have four black stripes on their wing covers. In their nymph stage, they are orange or reddish in color with black dots and eventually develop yellow stripes on their wing pads.
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These plant bugs feed on the leaves near the top of the Weigelia shrub, causing the spots to appear. The affected leaves may turn brown and die over time.
Remedy
To combat four-lined plant bugs effectively, it’s best to spray the shrub while the bugs are in the nymph stage and actively feeding.
Encapsulated pyrethrum can be used every 3 to 5 days until no more visible insects are present.
4. Cottony Masses & Mealybugs
Mealybugs are another pesky insect that can affect Weigela.
These bugs have oval, flattened bodies covered with white waxy powder and short, soft spines around their edges.
They sometimes gather in cottony white masses on the stems, branches, and leaves of Weigelia, sucking sap and weakening the shrub.
Infested leaves may appear yellowish, and heavily infested plants may not grow well.
Ants are often attracted to the honeydew secretions from the mealybugs, which can lead to mold growth on the foliage.
Remedy
To combat mealybugs, you can spray the shrub foliage with neem insecticide 2 or 3 times at 10-day intervals.
In late winter, when the shrub is dormant, spraying the bark surfaces with heavy horticultural oil can help kill overwintering eggs.
These measures can effectively control mealybug infestations.
5. Root Nematodes
Root nematodes are tiny worm-like creatures that burrow into the roots of Weigelia, gradually destroying the root system.
This can result in stunted growth, leaves turning reddish-yellow, and a weakened shrub.
Infested roots eventually die, and the shrub struggles to form new roots, leading to a hard-to-water, knotted root system.
Nematode attacks are most noticeable in hot weather when the shrub foliage appears to recover poorly from the heat.
Remedy
To control nematodes, you can use a commercial nematode control product, such as “ClandoSan,” which is effective and safe.
Sprinkle this granular product on the soil around the affected shrub, extending as far as the branches spread.
Gently scratch it into the top inch or two of soil, taking care not to damage the small feeder roots near the surface.
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Adding compost or leaf mold to the soil can also help control nematodes by encouraging beneficial fungi.
Additionally, drenching the soil with liquid fish emulsion can feed the plants and repel or kill nematodes.
6. Twig Blight
A blight disease caused by a fungus can cause the branch tips of Weigelia to turn brown and die back.
Unlike frost damage, this issue can spread and potentially even kill the entire branch or shrub.
Remedy
To control twig blight, it’s important to spray affected shrubs with a copper or lime sulfur fungicide when symptoms first appear.
Regular spraying every 10 days in wet seasons can help prevent the disease from spreading.
It’s also important to avoid overhead watering that wets the foliage and prune to increase air circulation around the shrubs.
Sterilizing pruning tools by dipping them in household bleach can prevent the spread of the disease.
Finally, removing and replacing the old mulch can also help prevent recurring outbreaks.
7. Root Rot
Soil-dwelling fungi can cause root and stem rot in Weigela.
This usually affects the stems near the soil level, causing yellowing, wilting, and eventual death of the foliage.
The root system can also rot, leading to the shrub toppling over.
Remedy
To combat root rot, it’s important to remove and discard infected shrubs or cut away affected plant parts using clean, sharp tools.
Disinfecting tools after use and keeping the garden free of old plant debris can prevent the spread of the fungus.
Additionally, providing good drainage by lightening heavy soil and avoiding overwatering can help prevent root rot.
Spacing plants further apart can also prevent crowding and reduce the risk of infection.
Final Thoughts
Remember, dealing with these issues promptly and effectively will help keep your Weigelia shrubs healthy and flourishing.
By taking the necessary steps to address these problems, you can enjoy the beauty of your Weigela garden for years to come.
Source: https://thelittle.garden
Category: Gardening