Grasshoppers are coming!

Saskatchewan Agriculture has published a grasshopper survey for the province and in 2012, the Meadow Lake area looks like it could be having an issue with this insect pest. Severe levels of this pest (greater than 24 per square meter) are likely. The first thing that any farmer or rancher needs to know is how to count this pest. Knowing how to count the pest will allow an estimation of what type of damage that might be expected in your fields. The how to of counting grasshoppers is easy. If you take steps that are about a meter long and you watch and count what jumps up in front of you, the numbers will be very close to the numbers per square meter. Once the grasshopper count is done, the crop and the condition of the crop must be looked at. If the grasshoppers are in a field where the growth is young, the numbers of grasshoppers that can do damage is low. I have seen fields with 2 grasshoppers per square meter have to be sprayed because the crop was being chewed of quicker than it could come out of the ground. As the crop gets more advanced, the numbers of grasshoppers that are required to make economic sense to treat goes up. Things like the price of the crop and the potential yield also need to be considered at this time. Canola looks like it could be over $12 per bushel this fall, so it doesn’t take many bushels to make up for the cost of spraying. Once the potential damage is assessed, the environmental influences must be looked at. If the fields are dry and there is no rainfall in sight, the benefit of spraying will be reduced. In hay fields, I have seen that cutting the crop is the best solution to a grasshopper problem in a dry field. You have to have more rain to grow more bushels or more bales. Grasshoppers that are in the 4th or 5th instar eat the most, so if the grasshoppers are older (have wings), the benefits of spraying are less or mare can be tolerated in a field. Spraying too early for a grasshopper infestation is a problem. When looking at the grasshoppers in a field, look for over 50% of the grasshoppers being over ½ long. If there is this type of size distribution in the grasshopper population in your field, it likely means that most of the hatch is done for the year. The key to dealing with a grasshopper infestation is to go out and look. If the grasshoppers are there at the appropriate count levels, it is time to spray. If you are uncertain, try and find someone with experience that can help you with the counts. If it looks like the grasshoppers need to be controlled with insecticide, contact your local honey bee operator to be sure that no bees are in your area. Honey bees pollinate your canola, so they are important to local farmers.

 

Dave Cubbon, P Ag