Last year, there were a lot of acres of canola sprayed for insects. So far this year, we do not see any amount of bugs in our canola fields but it is will be soon time to start checking. Each year is a different year so the only solution to finding out if your canola crop is at risk is to get out into your fields and check.
The insect that we have already had to deal with this season in many fields is grasshoppers. There were issues at crop emergence that needed to be dealt with. Since then, there are fields were we have seen grasshoppers move in from hay fields and ditches. The key to checking grasshoppers is to go far enough into the field. The edge of the fields have higher numbers. Spraying the whole field because the numbers are high on the perimeter of the field does not make sense. Remember, there needs to be 6 to 12 grasshoppers per square meter before spraying is recommended.
Last year, there were bertha armyworms in the area. This year, they could be back. It is important to get out and look for this pest for a number of reasons. First off the economic threshold for this insect is somewhere around that 20 to 25 larva per square meter. Lower numbers are not worth spraying. The other consideration with this insect is that they can be sprayed too early. Making sure the hatch of this insect is near complete is important to insure that the insecticide applied is used effectively. Remember to check a few areas in the field to ensure that the count is a good one.
Lygus bugs were another insect in our fields last summer. Too check for this insect, a sweep net is needed. To get an indication of how many insects are in a field, take your hat off, sweep it through the top of the crop and see if they are present. If they are in a field, a count should be done. If the bug shows up early and the numbers are high enough, the fields should be sprayed. The economic threshold for this insect is around 25 insects per 10 sweeps.
Diamondback moth larva are the last insect that can be found in canola fields at this time of year. They do damage to the pods. The numbers that are required to justify spraying for this insect are high (in the 200 to 300 per square meter range). Again, the only way to tell if this insect is going to be a problem is to go out in the field and check.
In general, our canola crops look good. Part of getting the top yielding canola field in the bin is to take care of the insects present. This means that producers must get into their fields in the next couple of weeks and start checking for insects. If the numbers are present, the fields are worth spraying.
By Dave Cubbon, P Ag