The Crucifer flea beetle is the most important insect pest of canola in North Dakota. The
beetles attack young seedlings shortly after emergence and may severely reduce
stands and yield. In a program led by
Jan Knodel at the NDSU North Central Research Extension Center and also conducted at the Carrington and Langdon Research Extension Centers, commercial seed treatments and a labeled
foliar spray are being compared for effectiveness. Normally, seed treatment adequately controls
flea beetles and the major concern is how strong a treatment formulation is
needed (more concentrated product = higher cost). However, the spring of 2003 was somewhat
atypical. The soil warmed up very slowly
and canola which was planted early (early May) did not emerge for approximately
three weeks in some fields. Since the
protection afforded by seed treatments may last approximately three weeks,
considerable flea beetle damage was observed in some fields planted with
treated seed. As a result, seed
treatments in combination with a foliar spray at the cotyledon stage produced
the best yields. The brand of seed
treatment chemical had a minimal effect on yield at Carrington, but the higher
rate tended to increase yield over the lower rate. Yields with foliar spray and no seed
treatment were also relatively good this season. However, timely application is critical. Weather conditions and other field operations
at this time of the year may affect the timeliness of spraying increase the
risk of relying solely upon foliar treatment.
During the past two seasons at Carrington,
flea beetles have attacked canola research plots shortly before physiological
maturity, causing severe damage in some instances. Due to pre-harvest interval restrictions, foliar
insecticides labeled for seedling treatment cannot be used at the end of the
season. Under the leadership of Dr.
Denise Olson, NDSU Entomology Dept., Fargo, a project was initiated at
Carrington, Minot, and Langdon to study the effectiveness of biorational treatments, including biological control
agents, vegetable oils, and kaolinite clay. As promising materials are identified, work
on application methodology will be intensified.