Gall Midge or Leaf midge of Blackcurrants
Gall or Leaf Midge of Blackcurrants — Shrivelling and twisted leaves
Galls on the leaf – normally regularly shaped domes above and sometimes below the upper surface – can be caused by a number of pests and diseases. Here we are interested in the ‘midge’ that causes galls on blackcurrant leaves. Galls sometimes materialize as larges round growths – such as the common Oak Apple gall. Cutting one of these open will reveal the maggot of the Oak Leaf Wasp, which lays its egg, then to develop into larva which causes the large gall.
Black Currant Leaf Gall
The Leaf Midge lays eggs which develop into small maggots on the Blackcurrants. These then find their way to the leaves for food, causing the young foliage to become distorted, twisted, and then turning black. The Blackcurrant Leaf Gall Midge is NOT the same as the Big Bud Mite
Eventually this causes death of the shoot and a general weakening of the plant — not always serious and control can be simply by taking off the infected leaves, where you will probably find the small creamy-white maggot inside, and destroying.
As with all midges, the Blackcurrant leaf Gall midge is not easily controlled for there is no chemical control available to home users. Affected growths can be cut off and burned.
Treatment with a systemic insecticide suitable for food crops — such as Provado — will also be an option. Do not use at blossom — pollinating time. Provado uses Thiacloprid as its main active ingredient, and this is less of a problem to pollinating insects. But do not use before flowers have finished. Until then, simply pick off leaves. If nothing else, this will ease the problem for next year.
Image shows typical damage by a Gall Midge. Not on a Blackcurrant in this instance.
Leaf Midge — or Gall Midge
Organic gardeners suggest a dilute spray of ordinary washing up liquid. Maybe that is better for visible aphids!
Whichever method of control you use, doing nothing is not really an option, for the affected leaves are at the soft growing tips, which are basically providing for next year’s growth. It is sometimes said that there is not enough of a problem for any concern.
Young growth is essential for the benefit of any plant, and weakening of the foliage on fruit bushes will lead to a less productive crop. Producing fruit takes energy – lots of it!
How to Manage Pests
Pests in Gardens and Landscapes
Honeylocust pod gall midge—Dasineura gleditchiae
Feeding by larvae of this gall midge (Cecidomyiidae) causes distorted, swollen growth of leaflets on honey locust, Gleditsia triacanthos. Established trees are rarely, if ever, killed by the galling, so damage can be tolerated.
Galls are most apparent during spring. Each distorted leaflet contains one to several pinkish white maggots up to 1/10 inch long. The oblong pupae are orangish to white and 1/10 inch long. Adult gall midges are delicate flies about 1/10 inch long with long, slender antennae and legs and a gray thorax with two black, lengthwise stripes.
Adults emerge from overwintering pupae in soil and most egg laying occurs during spring. By midsummer egg laying ceases, and plants often continue to produce new leaves that do not develop galls.
Larvae require succulent new terminals in order to feed and cause galls. Pupation of the spring and summer generations occurs within the galls. In the fall, mature larvae drop from galls or crawl to pupate under the tree canopy, within 1 inch of the soil surface. There are about six overlapping generations per year in California.
Infested leaflets form brown, green, or reddish galls. Heavily infested foliage turns brown and drops prematurely, leaving parts of branches leafless.
Avoid the Sunburst honey locust, which has bright yellow spring foliage. Sunburst readily defoliates in response to drought or temperature changes, as well as gall midge damage. Consider planting the Shademaster cultivar of honey locust, which appears to be less susceptible. Black locust, Robinia spp., are not infested by this midge.
Several species of parasitic and predaceous wasps feed on this pest. Because the gall midge has many generations and the larvae and pupae occur protected in galls or soil, this insect is not easily controlled with insecticides.
On small plants, narrow-range oil, or horticultural oil, sprayed to thoroughly cover terminals at intervals during about March and April kills gall midge eggs and can substantially reduce damage.
To increase the effectiveness of oil, properly time its application. Beginning in early March, monitor for the presence of adults by hanging at least two yellow sticky traps in the lower outer branches of honeylocust. Inspect each trap at least twice a week using a 10X hand lens or a dissecting microscope to view and identify the adults, described above.
Adult honeylocust pod gall midge
|Empty midge pupal cases|
Statewide IPM Program, Agriculture and Natural Resources, University of California
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