Current and previous environmental conditions are in favour of a grasshopper outbreak. Outbreaks usually occur after two or three years of hot, dry, summers and open falls. Dry weather increases the chance of egg survival which leads to greater severity of adult feeding. Open falls allow for more time for the grasshoppers to feed and lay eggs. Lentils and cereals are the main crops you should be monitoring and assessing grasshopper population levels.
The pods on the lentil plant are usually where grasshopper damage will occur, not so much on the foliage. It is estimated that the damage from grasshopper feeding on lentils is two percent for every one grasshopper/m2. Damage may be more severe on field edges as the hoppers move in from neighboring grassy areas, so be sure to scout far into the field to ensure control measures are taken only where necessary. Grasshoppers do the most damage to lentils during the flowering and podding stage. The threshold number is two grasshoppers/m2 during this stage.
When you are out scouting for grasshoppers, it is easiest to assess the amount of grasshoppers present by using a sweep net. Sweep in a 180 degree motion and count how many hoppers are in the net. Repeat this in multiple spots of the field to get a clear understanding of the potential damage.
Grasshoppers are a concern in cereals as well. Damage can appear as notching and stripping of leaves. The damage on the stem is a bigger concern when the stem is chewed all the way through right below the head of a maturing or mature plant. Scouting in cereals can be done in a similar way as in lentils. You can use a sweep net to help count the number of grasshoppers in a m2 area. Another common practice is to hold a meter stick in front of you while you walk to help you visualize how large a m2 area is and count how many hoppers jump out in front of you while you walk. Control measures should be considered when you are finding 8-12 grasshoppers in the field or 13-24 grasshoppers along the edge of the field or in the ditch.
Natural enemies are an important population control factor when it comes to grasshoppers. Some predators attack when the grasshoppers are still in the soil waiting for spring while other predators attack the nymph and adult stage. Bee flies, blister beetles, and crickets are the most common egg predators. Spiders, wasps and many birds feed on nymphs and adults.
Grasshopper forecast and monitoring maps are produced yearly to help predict the severity of the damage you should expect. In years when high grasshopper numbers are expected there are spring surveys of grasshoppers and grasshopper eggs. It is beneficial to keep an eye on these numbers so you are up to date with what is happening in your area.
If you are concerned about grasshoppers in your crops contact your local SynergyAG location!