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The cypress twig gall midge, Taxodiomyia cupressiananassa (Ostensacken) infests baldcypress and pondcypress in the midsection of the U.S. from Illinois to Florida and Louisiana. The flies overwinter as larvae on the ground in the galls, pupate in the galls in spring, and the adult flies emerge later in the spring for an extended period of time. The female midge oviposits on the new developing foliage and the midge larvae induce the gall formation by the leaflets (Figure 1).
Galls are light green to whitish in color and appear as small elongate swellings on the leaflets. Larger galls may reach greater than >3 cm in length and >2 cm in width. As the flies mature, they emerge from the galls to begin the second generation. The second generation begins during late July in north Florida. As the flies emerge form the galls, the galls turn brown and the leaflets also die. This causes the trees to become unsightly (Figures 2, 3 and 4 below).
Gall size is directly related to the number of flies that emerge from the gall, larger galls produce more flies. Galls produce an average of 16 flies and the pupal cases remain apparent on the exterior of the gall after adult emergence. The gall midge is heavily parasitized by several small wasps that emerge at the same time as the midges. As more cypress is planted we expect this gall midge to become more widespread as a pest. Controls should be applied to the foliage before the galls form during each generation. It appears that some genetic lines of cypress are less susceptible to the gall midge than others.
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