Producers encouraged to scout their fields for this pest due to recent weather conditions
By Kate Ayers
Staff Writer
Farms.com
Saskatchewan farmers could see increased flea beetle pressure in canola crops this year.
As a result of delayed seeding this spring, seedling emergence could overlap with the bulk of flea beetle emergence in select areas, a Government of Saskatchewan article said last week.
The province’s warm and dry conditions could also facilitate flea beetle feeding. Indeed, temperature is a large driver of beetle emergence.
Crucifer flea beetle emergence is highest when the soil reaches 15 C, the article said. Striped flea beetles can emerge four weeks prior to the crucifer flea beetle.
However, flea beetle activity is variable and emergence can last for weeks.
“Growers and agronomists should keep checking fields for damage,” Kevin Zerr, an agronomist with Agi-Care in Swift Current, Sask., said to Farms.com on Thursday.
“When the sun warms the plants in the morning, the flea beetles start to be active. They are small but easy to see if you are patient.”
These beetles prefer to feed on plants in the mustard family, including canola, volunteer canola, wild mustard or flixweed, the article said.
Crop damage occurs when a high population of beetles is present. To protect seedlings from flea beetles, seeds are often treated with neonicotinoids (either thiamethoxam or clothianidin). These products reduce the amount of damage caused by crucifer flea beetles but are less effective on striped flea beetles.
Farmers can also decide to use "higher end seed treatments, such as Visivio or Lumiderm, that have activity on striped flea beetle," Jennifer Bingham, the lead agrologist with Pioneer Co-op, said to Farms.com on Friday.
"We used to have all crucifer flea beetles that were easily controlled by the basic seed treatment package, but the population has now shifted to a high level of striped flea beetles."
Some companies also offer a "flea beetle guarantee on their treated canola seed and will cover the cost of the insecticide if one is needed," she added.
The pests must consume the seed treatments for them to have an effect. So damage can still occur if beetle numbers are high, the article said.
“Seed treating with regular treatments or the new, enhanced treatments have helped protect the small plants for awhile but eventually this protection wears off,” said Zerr.
“With the slow growth due to dryness, the plants are slow getting out of the gate. Plants are remaining vulnerable to feeding for a longer period of time.”
Producers are encouraged to scout their fields when the seedlings are young. Flea beetles leave “shot-hole” damage. They feed on cotyledons, first true leaves, petioles and stems, and could cause lower yields, the article said.
Growers should “look for feeding damage (holes or divots) on leaves and stems,” Bingham said.
Plants are most vulnerable to beetle damage during the first two weeks after emergence and farmers should scout diligently during this period.
Farmers are encouraged to examine 10 sites throughout the field and 20 plants at each of these sites.
“When scouting, start on the edges of the field and check in from there,” Zerr said.
“The flea beetles will often move in from neighboring fields that had canola, mustard or lots of certain weeds the previous year. The (beetles) can overwinter in a grass ridge, ditches or tree rows along the edges of a field.”
The action threshold is reached when 25 per cent defoliation has occurred across the field and beetles are still actively feeding, the article said.
“Visually, this looks like more than 25 per cent. It can be a very visually scary scene,” Bingham said.
“We have also told farmers to spray before this stage if the flea beetles are doing most of their damage to the stem. This (feeding) kills off the growing point and the plant, so the threshold is lower.”
If applied within the correct window, an insecticide application could help reduce plant damage.
“These sprays should slow the flea beetles down and allow the crop to move ahead in its growth,” said Zerr.
“The crop just needs to get growing to move ahead of this risk.”
When plants have reached the three- to four-leaf stage, they are much more tolerant to flea beetle feeding, the article said.
Government of Saskatchewan photo