Tips on how to use this section
The symptoms of the most common problems are in the left column of the chart. In the right column are the probably causes of those symptoms. For those problems for which there is detailed information in a different part of Yardener’s Helper, the name of the problem is linked to a detailed file. For those problems for which there are no additional files, the discussion is found in the paragraphs below the chart.
| Solving Firethorn Problems | |
|---|---|
| Symptoms | Probable Causes |
| Foliage Damaged In Winter | Wind Burn |
| Pale or Yellow Spots on Foliage | Aphids |
| Foliage Turns Pale or Mottled | Lacebugs |
| Leaves Stippled; Covered with Fine Webs | Mites |
| Small Bumps on Foliage; Leaves Drop | Scale Insects |
| Holes in Leaves and Stems | Webworms |
| Holes in Flowers; Leaves Rolled Up | Rose Leafroller |
| Flowers and Shoots Wilt Suddenly in Spring | Fire Blight |
| Black Patches on Leaves and Fruit | Scab |
Foliage Damaged In Winter means Wind Burn
Severe windburn may damage foliage during the winter but firethorn shrubs usually regenerate themselves in the spring. This problem can be controlled somewhat by surrounding each shrub with protective material such as burlap or white agricultural fabric. Spray leaves with anti-transpirant to retard water loss.
Holes in Leaves and Stems because of Webworms
Webworms are yellow-green caterpillars, about 1 inch long, covered with numerous black spots along their back and sides. They spin a thin silken web about the host shrub, webbing together both leaves and twigs, to protect themselves. Webworms are a major firethorn pest in the Southwest. They eat holes in leaves and stems, and cover foliage with silken webs as they feed. Some webworm nests can be handpicked and destroyed. To control the rest, spray foliage with Bt (Bacillus thuringiensis) spray as soon as hungry young caterpillars are visibly feeding on it. When they ingest the bacteria they will sicken and stop eating, then die within a day or two.
For more information see file on Dealing with Caterpillars.
Holes In Flowers, Leaves Rolled Up Rose Leafroller
Leafrollers are caterpillars of various moths that feed on and then pupate within rolled up firethorn leaves. Adult moths are brown or gray, 1/4 to 1/2 inch long. The larvae, the caterpillars, are dark to light green or cream to yellow, 3/8 to 1 3/4 inch long. Frequently there are 2 generations of this pest annually, one in spring and the other in late summer. Rose leafrollers chew holes in firethorn flower buds and roll up the leaves, binding them with strands of silk. Leaves become skeletonized, turn brown and drop in late summer, giving the plant a scorched look. Spray foliage surfaces with Bt (Bacillus thuringiensis) just before you expect the caterpillars to begin feeding. If it rains, apply Bt again. If there are not too many pests, crush them in their rolled-leaf hideouts.
For more information see file on Dealing with Caterpillars.
Flowers and Shoots Wilt Suddenly in Spring means Fireblight
This disease caused by a bacterium is spread by insects and rain. New shoots may wilt suddenly in late spring, turn black or brown and die. The dead leaves droop downward on the affected twigs. Plant resistant varieties of firethorn such as `Lalandi. 'If possible, destroy any nearby diseased and neglected pear, quince and apple trees, since they may harbor the fire blight organism. Between November and March, cut off affected branches at least 3 inches below the damaged area on affected firethorn shrubs. Discard diseased branches in the trash. Before each cut, disinfect the pruning saw or shears with a spray of household disinfectant. Spray sick shrubs with an antibiotic wettable powder, such as Agri-Strep, when 25% of the blossoms are open and at 5 to 10 day intervals during bloom.
Black Patches On Leaves and Fruit due to Scab
A scab disease caused by a fungus sometimes disfigures firethorn leaves and fruits. Spray berries with Bordeaux mixture when buds begin to swell and open and again 10 to 20 days later.
For more information see file on Dealing with Fungal Disease.
