Monday, August 9, 2010
Sawfly Sunday: What happened to my Saskatoons?
Ever wondered what happened to those Saskatoon berries with the little holes in their side? Well, chances are they were ruined by yet another in the myriad of sawflies that help gobble-up your garden. Several species of Hoplocampa sawfly (Tenthridinidae) including H. alpestris Rohwer, H. bioculata Rohwer, and H. pallipes MacGillivray, have been reported from saskatoons, but the only recent study I could find in the general neighbourhood of Alberta (fittingly from University of Saskatchewan in Saskatoon) was on a species that is supposed to feed on Choke Cherry (Prunus virginiana).
R.G. St. Pierre' and D.M. Lehmkuhl. 1990. Phenology of Hoplocampa montanicola Rohwer (Tenthredinidae) and Anthonomus quadrigibbus Say (Curculionidae) on their host plant Amelanchier alnifolza Nutt. (Rosaceae) in Saskatchewan Can. Ent. 122: 901-906.
St Pierre & Lehmkuhl report that adult sawflies emerged in mid-May prior to the period of peak flowering, fed and fooled around in the flowers, and laid one egg per flower during the period of petal drop in late-May. Larvae fed on about 2 fruit per infructescence and completed development by the end of June, just as the first saskatoons were beginning to ripen. The first fruit attacked was usually dropped, but the second was often retained on the shrub as a hollow shell. Larvae overwintered in the leaf litter. Almost half the fruit were ruined at one study site and I have noted similar levels of loss on my saskatoons. Whatever this species of Hoplocampa is, it is rather pretty, but on the whole I would rather have more saskatoons and fewer sawflies.