Controlling lygus bugs
Studies at the Winnipeg research centre have shown three species of lygus bugs can cause significant economic losses in canola in Manitoba.
Furthermore, a four-year study has recently shown controlling the major lygus species, Lyguslineolaris, is complicated because its generations are synchronized with the bud and flower stages of the canola crop.
The species has two non-overlapping generations in Manitoba. Only the second generation is found on canola.
During the first three weeks of May, adults which overwinter migrate onto weeds and other host plants to feed and lay eggs. Lygus bugs normally prefer host plants with growing tips and young foliage or with buds and flowers. In canola, they prefer the bud, flower and pod stages. This first batch of adults doesn’t hurt canola because the plants are too young.
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During the last two weeks of June, the overwintered adults disappear and are replaced by first-generation adults, which emerge from the last half of June to the end of July. At this time, canola is in the bud and flower stages and may be invaded by these adults over a period of several weeks. Egg-laying by first generation females continues until mid-August.
While canola is flowering, lygus bug populations are still relatively small, consisting mostly of adults. The second generation nymphs first appear in late July or early August, reaching high population levels when the canola pods are developing. This large population increase may result in significant damage to developing canola seeds, significantly reducing yield. Second-generation adults are found from the last half of August until they hibernate in October and November.
Because of the six-week period when first -generation adults can invade the canola crop, manipulating the seeding date to prevent damage is not a practical pest management strategy.
Using pesticides to control lygus bugs will depend upon sampling to determine whether population levels warrant the expense.
The most effective strategy is to sample soon after the end of flowering, when nymphal populations will indicate the damage second-generation adults can cause during podding.
– Agriculture Canada
