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2021: Year of the Lygus


Bug of the Month

By Dr. Héctor Cárcamo

Lygus bugs are native insects in Canada that feed on the buds, flowers and young seeds of most plants.

4th instar Lygus
Once the young lygus have visible wing pads and five dark dots on their backs they are big enough to feed on seeds

They are a perennial pest in seed alfalfa and occasionally in other crops like canola. In 2021, there are reports of high lygus numbers in greenhouses in Quebec, berry crops in Ontario, faba beans and flax in Saskatchewan and several canola fields in Alberta.

The pest species and number of generations vary with the local climate of the region.

In Alberta, they migrate to canola at early flower and generally there are less than one lygus per sweep at that time. At these normal numbers, their feeding does not affect canola and ther is no need to control. However, monitor the crops again near the end of flowering when lygus can potentially damage young seeds and reduce yield.

This year many canola fields had 2-3 lygus adults per sweep at early flower. This led to very high numbers of young lygus (they have five young stages called instars).

Many of the very tiny bugs probably die from rain or predators before they can feast on seeds.

Are high numbers of lygus at early flower a concern?

Canola is a highly resilient crop and given enough moisture can withstand lygus at early flower because canola aborts about half of its flowers even with no insects present.

But in a dry and hot year like 2021, canola may not tolerate such high lygus numbers; which may warrant a control action.

This situation does not arise often, so getting research data is a challenge. Thus, farmers may consider leaving check strips unsprayed near the middle of their fields. They should compare yields using their combine monitors; contributing to our efforts to better understand this enigmatic insect.

If you do this, please share your results with me, Dr. Hector Carcamo