Diana Pilson University of Nebraska dpilson1@unl.edu

Three tephritid flies feed in sunflower inflorescences in our study area:
Gymnocarena diffusa, Paracantha cultaris, and Neotephritis finalis.

Gymnocarena diffusa (Snow)

The largest seed-feeding tephritid in our study area is Gymnocarena diffusa. Adults are commonly seen resting on the underside of leaves during the day. Oviposition reportedly is greatest at midday. Larvae are usually found singly in an inflorescence. They tunnel beneath the receptacle and also down some distance into the petiole. Larvae development takes an average of 30 days, after which the larva form a hole in the back of the flowerhead and drop to the soil, where they form a black puparium (7mm in length). If unable to drop from the head, the puparium may be positioned within the receptacle protruding through a central dark-ringed hole.

Cross sections of flowerheads with damage by G. diffusa:
Larval damage to receptacle Larva inside receptacle

             

Paracantha cultaris (Coquillett)

P. cultaris larvae feed on immature florets and the receptacle, and form a black puparium similar to that of G. diffusa. In P. cultaris, however, the puparium is smaller (4-5 mm) and is formed in a frass-packed cavity excavated between seeds. This species was first collected at CPBS in 1999. It is not commonly collected in flowerheads older than 25 days, indicating a shorter time to eclosion than G. diffusa. Also, more than one puparium from this species can be found in an inflorescence at our site. It is the least common of our three tephritids, but is also recorded from Helianthus in much of the western U.S. (AZ, CA, CO, ID, OR, NM, TX, UT, WA) south to Costa Rica (Foote et al., 1993). Cavender and Goeden (1984) state that each larvae destroys an average of 34 disk florets.

Neotephritis finalis (Loew)

N. finalis (sunflower seed maggot) is common in sunflower at CPBS. It is the smallest of our tephritids. Several larvae can occur together in a flowerhead. Larvae feed within undeveloped ovaries, often completely consuming the floret before the seed is fertilized. The species is found in much of the U.S. and also in southern Canada and northern Mexico (Foote et al., 1993), and has been recorded from over 20 species of Asteraceae (Goeden et al., 1987). The puparium of N. finalis is light brown and around 3.5 mm in length.

 
Larvae feeding Normal ovary (LEFT), Damaged ovary (RIGHT) with extracted larva (L)

Tephritid references:

Cavender, G. L., and R. D. Goeden. 1984. The life history of Paracantha cultaris (Coquillett) on wild sunflower, Helianthus annuus L. ssp. lenticularis (Douglas) Cockerell, in southern California (Diptera: Tephritidae). Pan-Pac. Entomol. 60 (3): 213-218.

Foote, R.H., F.L. Blanc, and A.L. Norrbom. 1993. Handbook of the fruit flies (Diptera: Tephritidae) of America north of Mexico. Cornell University Press, Ithaca NY.

Goeden, R.D., T.D. Cadatal, and G. A. Cavender. 1987. Life history of Neotephritis finalis (Loew) on native Asteraceae in southern California. Proc. Entomol. Soc. Wash. 89 (3): 552-558.

Kamali, K., and J.T. Schultz. 1974. Biology and ecology of Gymnocarena diffusa on sunflower in North Dakota. Ann. Entomol. Soc. Am. 67 (4): 695-699.