Friday, 8 May 2020

Flea beetles

Flea Beetles (Chrysomelidae: Phyllotreta species) – As canola seedlings emerge, scout for flea beetle damage on cotyledons but also on the stem (Fig. 1, left).  Two species, Phyllotreta striolata (Fig. 1, right) and P. cruciferae, will feed on all cruciferous plants but they can cause economic levels of damage in canola seedlings.

Figure 1.  Flea beetle feeding on leaves canola seedling resulting in "shot-hole" damage plus girdling of stem (left) plus dorsal view of striped flea beetle (right).

Remember, 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 (copied below for reference) produced by Dr. J. Soroka (AAFC-Saskatoon)  - take it scouting!
Figure 1. Canola cotyledons with various percentages of leaf area consume owing to 
flea beetle feeding damage (Photo: Soroka & Underwood, AAFC-Saskatoon).

Figure 2.  Percent leaf area consumed by flea beetles feeding on canola seedlings 
(Photo: Soroka & Underwood, AAFC-Saskatoon).

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.