Anguina amsinckia

Schizomyia macrofila

The fiddleneck gall nematode (Anguina amsinckia), also native to California, induces the weed to form floral galls that replace the flowers. Although the mechanism is somewhat of a mystery, feeding by Anguina in the flowers apparently stimulates the floral tissues to form a gall that encloses the nematode. Two complete life cycles take place within the flower galls, and about 40,000 nematodes occur in an average 3/8-inch-diameter gall. 

(T)he nematode had been known to attack only common fiddleneck, Amsinckia intermedia (A. menziesii), but we now know it attacks two other important weeds, Amsinckia lycopsoides and A. gloriosa (now considered a variant of A. tessellata). In addition, there may be different races of the nematode that are host-specific to different fiddleneck species or populations.

During our survey we also encountered a gall midge (Schizomyia macrofila) that feeds on fiddleneck and produces galls. Galls formed by the larvae are superficially similar to those formed by the nematode (Anguina amsinckia). However, the midge galls do not replace the flowers as do the nematode galls. Instead, almost any aboveground portion of the weed may form midge galls containing one or more orange-colored larvae. 

Few researchers have studied this gall midge, and its host range is not certain. Before our survey, only Amsinckia lycopsoides was reported to be a host. We found the midge on A. intermedia near Bakersfield and on A. spectabilis near Bodega Bay. 

Biological control of fiddleneck