Helicoverpa is the only major insect pest of chickpea. Research has shown that the impact of one helicoverpa larvae (per square metre) completing development on the crop is a resultant loss of 2 grams of grain. This figure is used in estimating the potential yield loss and subsequently the economic threshold. The following calculator can be used to identify potential yield loss and provide an appropriate suggestion for action.
Steps in determining if control is warranted:
- Sample the crop and record the number of larvae of each size in each sample (e.g. 5 beatsheet samples of metre row).
- Average the number of each size of larvae and enter into the relevant box.
- Enter the crop’s row spacing (100 cm is provided as a default value).
- Add your estimate of the cost of control (including application) and expected crop value to calculate potential yield loss and break-even economic threshold.
- If you have a preferred cost:benefit, enter it to get a revised economic threshold (1.5 is provided as a common example).
- The calculator generates a comment on action for both break-even and alternative thresholds. If larval density exceeds either threshold, an option to enter crop stage will become available.