Flea beetles

Newly emerging Brassicaceae but especially canola is attractive to overwintered flea beetles that emerge and become active early in the spring. As canola seedlings emerge, in-field scouting becomes crucial! If flea beetle densities are high, seedling damage levels can advance quickly – even within the same day! The cotyledon stage of canola is vulnerable to flea beetle feeding. Be sure to check out the Insect of the Week – Week 2 featured flea beetles!

Several species of flea beetles are present across North America. Be on the lookout for flea beetle damage resulting from feeding on canola cotyledons but also on the stem (Fig. 1).  Two species, Phyllotreta striolata (Fig. 1) and P. cruciferae, will feed on all cruciferous plants but they can cause economic levels of damage in canola during the seedling stages.

Figure 1. Flea beetle feeding damage (L) and striped flea beetle (R).

The Action Threshold for flea beetles on canola is 25% of cotyledon leaf area consumed.  Watch for shot-hole feeding in seedling canola but also watch the growing point and stems of seedlings which are particularly vulnerable to flea beetle feeding.

Estimating flea beetle feeding damage can be challenging.  Using a visual guide to estimate damage can be helpful.  Canola Watch circulated this article but also use the two images (Figs. 2 and 3; copied below for reference) produced by Dr. J. Soroka (AAFC-Saskatoon)  – take it scouting!

Figure 2. Canola cotyledons with various percentages of leaf area consume owing to flea beetle feeding damage (Photo: Soroka & Underwood, AAFC-Saskatoon).
Figure 3.  Percent leaf area consumed by flea beetles feeding on canola seedlings (Photo: Soroka & Underwood, AAFC-Saskatoon).

Access biological and pest management information posted by Alberta Agriculture and Forestry, Saskatchewan Agriculture, or Manitoba Agriculture and Resource Development, or the Canola Council of Canada’s Canola Encyclopedia. Refer to the flea beetle page within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (Philip et al. 2018) as an English-enhanced or French-enhanced version.

Two other favourite flea beetle resources relevant to field crop protection include:

Those armed with a stereomicroscope who are keen to monitor flea beetle species may wish to bookmark the “Common flea beetles of North Dakota” (Fauske 2003) which an excellent online resource and includes many of the commonly observed species of flea beetles also present across the Canadian prairies.

Soroka, J., Grenkow, L., Otani, J., Gavloski, J., & Olfert, O. (2018). Flea beetle (Coleoptera: Chrysomelidae) species in canola (Brassicaceae) on the northern Great Plains of North America. The Canadian Entomologist, 150(1), 100-115. doi:10.4039/tce.2017.60