Chrysanthemum Diseases - midge galls and fungus gnats

Two pests which can make damaging attacks on both plants and blooms are midges and gnats.
The Leaf Gall Midge Diarthronomyia chrysamthemi, was introduced from the U.S.A. and once established, can prove very difficult to eradicate. In recent years it has become a considerable problem in most of the chrysanthemum growing parts of Australia, and has been noted by several growers to have proliferated in just the last two years. The female Midge can lay as many as 150 eggs, which hatch out in five or six days, and generations of midges quickly overlap one another with successive laying of eggs taking place. Eggs are laid in leaf folds, or among the bracts of buds. When the larvae develop, they burrow into the fleshy part of the plant and establish a little chamber, causing the characteristic white thorn-like galls on the upper surface of the leaves or on the stem, like pimples on the leaf. The Leaf Gall Midge breeds throughout the whole growing season, reaching its peak in midsummer and, if left unchecked, a heavy infestation will take place, badly distorting blooms and stems. Introductions of cuttings from outside sources are the usual cause of an outbreak so it is essential that careful examination be taken of all new stock, destroying any badly infected cuttings. To control plants that are showing first signs of the leaf gall, a rigorous six-week spraying programme is essential to overcome the overlap of the emerging and breeding midges. The most suitable insecticide to use is LEBAYCID which actually penetrates the leaves and stems, thus destroying the eggs and will, if sprayed at weekly intervals for six weeks, clear up the problem. It will be necessary to carry out all usual safety precautions as detailed on the instructions. With respect to Fungus Gnats Sciarids, they will attack young seedlings or newly rooted cuttings. The gnats are attracted to sterilized soil, manure and peat. They lay their eggs on the organic material and the larvae then damage cuttings or seedlings by feeding on the roots. Effective control can again be achieved by drenching the soil with Lebaycid. Compost or soil must be well watered before drenching. Two applications may be necessary, two weeks apart. Dosage for both treatments is a rate of 5ml. to 7 litres of water. Many Tasmanian growers have found that METASTYSTOX is also effective at destroying Leaf Gall Midge.

Midge Galls and Fungus Gnats in Chrysanthemums by George Harrington
Two pests which can make damaging attacks on both plants and blooms are midges and gnats. The Leaf Gall Midge Diarthronomyia chrysamthemi, was introduced from the U.S.A. and once established, can prove very difficult to eradicate. In recent years it has become a considerable problem in most of the chrysanthemum growing parts of Australia, and has been noted by several growers to have proliferated in just the last two years. The female Midge can lay as many as 150 eggs, which hatch out in five or six days, and generations of midges quickly overlap one another with successive laying of eggs taking place. Eggs are laid in leaf folds, or among the bracts of buds. When the larvae develop, they burrow into the fleshy part of the plant and establish a little chamber, causing the characteristic white thorn-like galls on the upper surface of the leaves or on the stem, like pimples on the leaf. The Leaf Gall Midge breeds throughout the whole growing season, reaching its peak in midsummer and, if left unchecked, a heavy infestation will take place, badly distorting blooms and stems. Introductions of cuttings from outside sources are the usual cause of an outbreak so it is essential that careful examination be taken of all new stock, destroying any badly infected cuttings. To control plants that are showing first signs of the leaf gall, a rigorous six-week spraying programme is essential to overcome the overlap of the emerging and breeding midges. The most suitable insecticide to use is LEBAYCID which actually penetrates the leaves and stems, thus destroying the eggs and will, if sprayed at weekly intervals for six weeks, clear up the problem. It will be necessary to carry out all usual safety precautions as detailed on the instructions. With respect to Fungus Gnats Sciarids, they will attack young seedlings or newly rooted cuttings. The gnats are attracted to sterilized soil, manure and peat. They lay their eggs on the organic material and the larvae then damage cuttings or seedlings by feeding on the roots. Effective control can again be achieved by drenching the soil with Lebaycid. Compost or soil must be well watered before drenching. Two applications may be necessary, two weeks apart. Dosage for both treatments is a rate of 5ml. to 7 litres of water. Many Tasmanian growers have found that METASTYSTOX is also effective at destroying Leaf Gall Midge.