How To Boost Beneficial Insect Populations

Lloyd Dosdall, associate professor at the University of Alberta wants you to consider both the good and bad insects out in the field. He recommends farmers follow good production practices, to produce a healthy, vigorous crop that can better withstand crop pests. Why? Because these practices also benefit populations of beneficial insects. Here are his tips for encouraging beneficial insect populations.

1. Develop competitive crop stands. Healthy, well-nourished crops can better withstand attack by insect pests and can better compensate for pest attack than crops under stress. Use recommended seeding and fertility rates, seed early, and use certified seed of vigorous varieties to give crops an important competitive advantage over insect pests. A competitive crop stand can reduce the need for insecticidal intervention, and fewer insecticide treatments will enable populations of natural enemies of pests to build up in cropping systems over time.

2. Monitor crops carefully, especially when insect populations are at or near threshold densities. By determining the abundance and species diversity of pests attacking the crop, and assessing the vigour of the plant stand, agrologists will have a greater ability to forecast the risk of damage by one or more pest species attacking the crop.

3. Consider natural enemy populations when making assessments of threshold levels. Natural enemy densities are rarely monitored along with pest species, yet they have great potential for minimizing the need for insecticidal intervention. By monitoring their abundance, a more realistic assessment of crop risk can be derived.

4. Time insecticidal applications to have the greatest possible effect on insect pest numbers, while minimizing damage to non-target and beneficial species. Intimate knowledge of the life histories of the different species attacking a crop at a particular time of crop development is an essential prerequisite for making sound management decisions. This understanding of insect pest population dynamics can help determine the need to apply insecticide and the best time to apply it to achieve the greatest impact on all of the pest species involved.

5. Utilize cultural practices that enhance natural enemy populations. These include maintaining taller stubble for enhancing populations of wheat stem sawfly parasitoids, using trap crops for cabbage seedpod weevil control and using reduced tillage for enhancing natural enemies of cereal leaf beetles and root maggots. In addition, it is important to maintain natural areas adjacent to crops where flowering plants can provide a nectar source for parasitoids, and where predatory beetle populations can thrive and then invade crops to attack pests.

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