Skeleton Gall Midge
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Common Name: Skeleton gall midge. (1)
Type of Agent: Insect / gall midge (Diptera: Cecidomyiidae) (1-3)History: The skeleton gall midge was released in 1975 in the U S for the control of skeleton weed. (1-3)
Native Distribution: The countries the insect come from are Greece, Iran, Turkey, Southwest Poland, and in the western part of Yugoslavia. (1-3)
Origin: Greece (1-3)
Over wintering Stage: Mature larva, pre pupil, or pupil stage. (1)
Life beginning: The female inserts her eggs into the rosette, stem leaves, and stems. The incubation period lasts up to nine days. (1)
Egg Stage: The female adult can lay about 100 eggs per year. They lay them in the leaves, stem, or the rosette. Once they have been distributed, the eggs will hatch in about nine days. The eggs are an oval shape and are about 0.01 mm (.0004 in) x 0.02 mm.(.0008 in) in diameter. (1-3)
Larva Stage: Once the eggs have hatched, the larvae will feed on the tissue part of the leaf. The larva are flatten, 1- 2.5mm (.04 to .10in) long. The more these galls eat, the bigger they will get. They will be a yellowish color, pink, orange, and or occasionally they will be maroon. The larva will be done growing within four to seven days. (1)
Pupil Stage: After the mature larvae leave the gall they pupate. Most of them pupate in cocoons that are made of silk. The pupa break the cocoon tissue with their horns. The pupil case can sometimes be seen half way out of the exit hole after the insects left. The pupil time lasts from four to six days. (1)
Adult Stage: Adults live in the fields from the time period of about April to October each year. Females live three to four days, and males one to two days. Adults are small light to medium brown and lightly shiny. Females are .82 mm to 1.64 mm (.03 to .07 in) long and males are 1.03 to 1.56 mm (.04 to .06 in.) long. The male's bodies are long and slender with the genitalia readily visible. (1-3)Collection Techniques:
1. monitor collection site to see if native insects are doing any damage to the skeleton weed.
2. Collect leaves and stems of the skeleton weed. Make sure that the skeleton weed midges are in the pupil stage to reduce death rate.
3. Place the materials in a cage or secluted area and watch for emergencies.
4. First collect most adult insects and test them to see if the right species is being released. Keep samples, you may need them. When the midges emerge be around so that they are properly introduced to the galls that you had kept.
5. As soon as the midges emerge and are correctly identified they can be released to the infested area. (1-3)
Host: rush skeleton weed (Chondrilla juncea) (1)
Distructive Stage: The larval stage is the stage at which the insect is most damaging to the weed. (1)
Plant Species attacked: The insect infects all rush skeleton weed bio-types in the Western United States. (1) Site of Attack: The parts of the plant that are effected are the leaves and stems. (1-3) Impact on the Host: The midge damages the rosette and flower stem. (1)
Lenhard, Gerald. Louisiana State University. www.forestryimages.org
USDA Forest Service Archives. www.forestryimages.org - Any commercial or other use of the images requires the written permission of the photographer or contact organization, and The University of Georgia.
(1) Rees, Norman, et, al., Ed., Biological Control of Weeds in the West, Western Society of Weed Science, in cooperation with USDA, ARS, MT Dept. of Ag, and MT State Univ., Bozeman, Color World Printers, Bozeman MT, Feb, 1996.
(2) Breitenfeldt, Todd, Personal Interview, Whitehall Schools science teacher, E-mail: firstname.lastname@example.org, S-mail: mtwow.org: Whitehall Schools, P.O. Box 1109, Whitehall, MT 59759, (406)287-3862.
(3) Rees, Norman, et., al., Ed., Biological Control of Rangeland Weeds in the Northwest United States, Manuscript/ Rough Draft. 1996.
By: Austin Lewton 1/14/02. updated by: Samantha Terrel 2-28-07.
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