Insect Monitoring & Control
General Information:
- Grasshoppers, potato aphids, leafhoppers, bertha armyworms and Lygus bugs are the most common pests affecting flax.
- When you are scouting your fields for disease, you should also be scouting for insects. If you find insects in your other crops, it is important to also check your flax fields.
- For more information on field scouting techniques, please refer to your Provincial Guide to Crop Protection
- When considering whether to apply an insecticide it is very important to pay attention to pre-harvest interval.
- The pre-harvest interval is the number of days that must pass between the last application of a pesticide and harvest. For more information, please refer to your Provincial Guide to Crop Protection
Grasshoppers:
Grasshoppers have the potential to be a problem this year. The risk appears lower in Saskatchewan than Manitoba and Alberta. Within Saskatchewan, the risk is higher in the south west and west central regions.
2015 forecast maps:
- Alberta
- Saskatchewan
- Manitoba
- When scouting, it is important to look for grasshoppers.
- If you find grasshoppers in your other crops, it is important to check your flax fields as well.
- Grasshopper feeding can be very damaging to your flax crop, especially in the green boll stage as bolls may be clipped off, directly reducing yield. A nominal threshold of approximately 2 grasshoppers per m2 on average has been suggested if grasshoppers are clipping flax bolls.
- As with control of other insects, it is important to pay attention to pre-harvest intervals.
Potato Aphids:
- Although this is not an annual problem, flax fields should be checked for aphids and economic threshold levels should be monitored.
- The economic threshold is the density of insects that economically justifies control measures.
- Lower number of aphids may result in losses when they are feeding at the base of the bolls.
- Aphid numbers are surprisingly high considering how dry it has been this year.
- When scouting your fields, be on the lookout for aphids.
- At full bloom, 2-3 aphids per main stem if the flax plant has tillers (or 2-3 aphids per plant if there are no or very few tillers) is the economic threshold warranting consideration for spraying.
- At green boll stage, 8 aphids per main stem if flax has tillers (or 8 aphids per plant if there are no or very few tillers) is the economic threshold warranting consideration for spraying.
Leafhoppers:
- Aster leafhoppers can carry the vector causing asters yellows disease in flax.
- The aster leafhopper moves into Western Canada on air currents. They are mainly a concern when they arrive already infected with the aster yellows phytoplasma and can spread the disease to flax.
- Favourable wind currents occurred early in April 2015 so leafhoppers may be present.
- There have been reports on leafhoppers but no clarification as to whether they are aster leafhoppers or if they are infected with phytoplasma.
- Early feeding by leafhoppers could be an issue in disease spread.
- Currently, spraying is not recommended although this may change if;
- More leafhoppers arrive on wind currents.
- Leafhoppers move back into the fields.
- This year, leafhoppers may not be infected with phytoplasma and as such may not pose a risk to the flax crop.
Bertha Armyworm:
Lygus Bugs:
- Generally not a major issue in flax.
- Research has indicated that under good growing conditions, little economic damage may result from infestations as high as 100 Lygus bugs/10 sweeps. It is uncertain whether this tolerance extends to flax growing under stressed conditions.
- If Lygus bugs are found to be high in nearby canola or alfalfa fields, you should scout your flax fields.
For more information, including pictures of flax insect pests, please refer to the Flax Grower Guide Chapter 7 – Field Insect Pests, which is posted on the Flax Council website.
