The following is a summary of further comparisons of baiting techniques for the spotted wing drosophila Drosophila suzukii.  Previous posts have evaluated the use of various fruit purees and other mixes and these have determined that a mixture of one 2.5 oz packet of yeast + 4 teaspoons sugar + 12 ounces of water distributed in four or five Mason jars were very effective in monitoring and evaluating infestation levels of spotted wing drosophila.

Another test of baits was run last week.  Traps (a 500 ml Nalgene bottle with 4 holes in the lid) containing one pellet torula yeast (see photo below) dissolved in 100 ml water, the yeast + water + sugar bait mixture mentioned above and finally a commercial “filth fly mix” called Yellow Muse (AgBio Corporation) allowed to cure for several weeks (the fermentation process of this material may be important) were placed November 3, evaluated November 6 and then again evaluated November 9.

The results are shown below (numbers in columns refer to average numbers of flies captured in each trap):

“Females” means that they are vinegar flies without spots on the wings and assumed to be spotted wing drosophila (SWD), while males were readily identifiable with spots on the wings.

Treatment	11-06-09 SWD “females”	11-06-09 SWD males	11-06-09 SWD total	11-09-09 SWD “females”	11-09-09 SWD males	11-09-09 SWD total
Torula yeast	2 a	2.5 a	4.5 a	2.3 a	0.5 b	2.8 b
Yeast + sugar + water	2 a	1 a	3 a	7.8 a	24.8 a	32.5 ab
Filth fly mix	4.5 a	15.3 a	19.8 a	17.8 a	30.3 a	48 a

Means followed by same letter do not significantly differ (P=.05, Student-Newman-Keuls)

From the chart above, it is apparent that the torula yeast is not very attractive to spotted wing drosophila, while yeast + sugar + water continues to be, along with well cured Yellow Muse filth fly mix, the most useful.

Dry, "torula" yeast

Packet of Yellow Muse fly bait