Fig Leaf Blight Control: Learn About Leaf Blight Of Figs

Fig Leaf Blight Control: Learn About Leaf Blight Of Figs

By: Amy Grant

Fig trees are hardy to USDA zones 6 to 9 and reside quite happily in these regions with few serious disease issues. Learn how to spot the symptoms of figs with leaf blight and about fig leaf blight control.

What is Fig Thread Blight?

Fig trees (Ficus carica) are deciduous shrubs to small trees, native to the Mediterranean where they enjoy the warm temperatures of the region. When these warm temperatures collide with damp conditions, trees may become susceptible to leaf blight of figs.

Leaf blight of figs, sometimes referred to as thread blight, is caused by the fungi Pellicularia kolerga. It is fostered by hot, damp weather.

Fig thread blight first appears as yellow water soaked lesions on the foliage of the plant. As the disease progresses, the underside of the leaves turn tan to light brown in color and is covered in a light fungal webbing, while the surface of the foliage becomes covered with a thin silvery white mass of fungal spores. Further into the infection, the leaves shrivel, die and drop from the tree. Often, the affected dead leaves seem to be matted together.

While the most obvious damage is to the foliage of the plant, the fruit may also become affected by the fungus, especially if the fruit is newly formed and at the end of an infected leaf or stem tip.

Fig Leaf Blight Control

Figs with leaf blight do not respond to the use of fungicides. The only method of control is proper sanitation which will not eradicate the disease, but rather control it and reduce losses. Rake up and destroy any fallen leaves to keep the infection from spreading.

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Diseases of Ficus Leaves

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Ficus plants (Ficus spp.) have attractive green leaves which may unfortunately suffer from several diseases. Most types of ficus, including edible figs (Ficus carica), grow well in Mediterranean climates. Common edible figs are hardy in U.S. Department of Agriculture plant hardiness zones 8 and above, although some cultivars are hardy down to zone 5. If your ficus has diseased leaves, you can identify and attempt to control the problem. Temperatures below 40 degrees Fahrenheit may also cause leaf spots and distortion.

Fruiting or a Lack of Fruiting

If you look for blossoms on your fig tree, you probably won?t find them — they are inside the fruit.

A number of conditions may cause the fruit not to ripen or to drop prematurely. The following are the most common in Georgia in order of importance:

  1. Young, vigorous plants and over-fertilized plants will often produce fruit that drops off before maturing. If the plants are excessively vigorous, stop fertilizing them. Quite often, three or four years may pass before the plant matures a crop because most figs have a long juvenile period before producing edible quality fruit. If the distance between the nodes (leaves) on the current season?s shoots is more than 3 inches, the plant is probably excessively vigorous.
  2. Dry, hot periods that occur before ripening can cause poor fruit quality. If this is the case, mulching and supplemental watering during dry spells will reduce the problem.
  3. The variety Celeste will often drop fruit prematurely in hot weather, regardless of the quality of plant care. However, it is still one of the best varieties.
  4. An infestation of root-knot nematodes can intensify the problem when conditions are as described in items 2 and 3 above.
  5. You could have a fig plant that requires cross-pollination by a special wasp. If this is the case, then it will never set a good crop. The best way to resolve this is to replace the plant with one from a rooted shoot of a neighbor?s plant you know produces a good crop each year. This is a rare problem.

Dealing with fig pests and diseases

SA’s fig-growing industry, although relatively small, produces a significant harvest for export. Here are useful tips to treat diseases and pests on this plant.

The fig tree borer (Phryneta spinator) is a major pest of fig trees. Photo: Paul Donovan

The fig is a large deciduous tree. The edible fig itself is actually not a fruit, but the mature ‘infructescence’ of the tree – a hollow, fleshy structure lined on the inside with tiny flowers. A small opening allows the fig waspto enter and pollinate the flowers. Once pollination has taken place, the seeds develop.

A fig tree can suffer from several diseases:

This is a group of fungal diseases that cause black/brown spots on the leaves, which gradually turn yellow and wilt. Treat with a fungicide.

Fig rust
The leaves develop small orange spots that increase in size as the season progresses. The leaves themselves may droop. Fig rust can be controlled with copper-based fungicides.

Fig mosaic
This is caused by a virus that produces blotches on the leaves. The virus is spread by mites and the only way to treat it is to kill the mites with miticide or horticultural oil.

Endosepsis is spread by the pollinating wasp that enters the green fig to lay eggs. When the wasp dies inside the fig, the fungus develops on its body. The tree should be destroyed and the surrounding soil treated with a fungicide. Do not replant for 12 months.

Aspergillus is a fungus that causes the flesh on the inside of the fig to turn green and then powdery. If left untreated, the ripe figs rot and the tree sheds its leaves. Treatment is as for Endosepsis.

Phomopsis canker
This fungus enters the tree through pruning wounds or injuries. The infected bark develops sunken growths of dead tissue around the wound. Removing the infected branchesis the most effective way of controlling phomopsis canker.

Insect pests
Pests can be as great a problem to fig trees as fungal and viral infections. They include several species of beetle, fig scale, spider mite, vinegar flies and nematodes. A serious and common pest is the fig tree borer (Phryneta spinator). The female lays its eggs near the base of a branch. They take about two weeks to hatch and the larvae then feed on the bark before tunnelling into the tree.

Control is difficult when the larvae are in the tree. Squirt insecticide into the tunnels with a syringe (after first testing it on a leaf to ensure that it will not harm the tree). Enclose the lower portion of the tree in shade netting to prevent the female from laying her eggs in the bark. Make sure that the netting does not touch the tree if it does, the female will still be able to land on the bark and lay her eggs.

Encircle the top of the netting with silver foil coated with Vaseline to keep the beetles from breaching it. Laying shade netting on the ground around the base of the tree will also help to stop newly emerged beetles from climbing the tree. The fig tree borer has very few natural enemies, although a parasitic fungus called Isaria and several species of parasitic wasps can attack the larvae.

Paul Donovan, a Botswana-based biologist, advises farmers on pest control.

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"The most common disease of fig in the southeastern United States is the fig rust (Cerotelium fici).
Fig rust turn leaves brown, can cause defoliation and premature
ripening of the fruit, and decreases cold tolerance. This disease can be
controlled by a 5-5-50 Bordeaux spray (copper sulfate, lime and water)
applied every two to three weeks.

Other fig diseases include Botrytis cinerea (fungus) and Cercospora leaf spot fungus (Cercospora fici), which causes branch terminals to turn black and die. Thread blight (Pellicularia koleroga) results in necrosis of stems and matted foliage. Botryosphaeria dothidea (fungus) causes necrosis of leaves and stems. Rhyzopus stolonifer (smut) causes fruit drop of cultivars with an open eye. Fusarium spp. and Aspergillus niger are fungus that attack ripe fruit."