Lily Beetle Updates by Ian Wise

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Research Report - Fall 2025 

Over the past few months the contribution of many lily growers has continued to provide a better understanding of the lily beetle ecology in the province. Although subtle to most humans, the beetle appears to be responding to slight changes in the environment: most specifically to early warming trends. These slight changes are hav ing a noticeable impact on the timing of the spring emergence of overwintering adults. The diligent work by Deborah Petrie and B. J. Jackson found adult beetles emerging in large numbers as early as the last week in April in Brandon, where snowmelt had exposed bare soil in areas with overwintering adult beetles. Over six weeks later a small number of adults were found in Winnipeg. These beetles had only recently emerged, as indicated by the presence of eggs in the females and the absence of eggs on surrounding lilies. The Winnipeg site was heavily covered by leaves until late May. While this is not a definitive indication that the beetles are responding to climate effects only, it does add to the amount of information that gardeners can con trol, to some extent, when the beetles emerge and when to use management strategies to minimize the ability of the beetle to damage plants or become established in their garden. This information also shows that the beetle remains a threat, but through constant vigilance by all gardeners, every lily grower can help to prevent the beetle from becoming an impediment to growing lilies in the future. And that includes making sure that you do not unwittingly introduce the beetle into your garden by buying in fested potted plants. This problem was the primary source of initial infestations of the beetle in Manitoba, but fortunately, is now a lesser concern because of the decline of beetle populations in areas where the infested plotted plants originated. 

May 2025 UPDATE 

Capturing a Moment in Nature 

Once in awhile a photograph captures a rarely scene but common event in nature that arouses our curiosity. During one of her garden inspections this year Deborah Petrie of MRLS took a picture of an insect feeding on a lady beetle on a martagon. That is odd in itself because lady beetles are usually the predator and not the prey. And their bright colouration is a warning to predators, particularly birds, to not eat them because of their foul taste. Obviously, this had no bearing on the predatory insect, which consumes the internal part of the beetle through the insertion of its proboscis after partially digesting it with enzymes injected into the lady beetle.

So, what is this predatory assassin bug? It is not a species of a family of true bugs with this name but is an immature stage or nymph of a species of a family quaintly known as damsel bugs. In this picture it is difficult to determine who is friend or foe, as humans often do. Damsel bugs are native species that are opportunistic consumers of many insect species. As a consequence, they do not have an ecological effect on any one species or single group of similar species. Conversely, lady beetles are known as important predators of aphids and help to reduce damage caused by these insects to many garden plants. But upon closer scrutiny this lady beetle is a species known as the seven-spotted lady beetle; a Eurasian species deliberately introduced into North America in an ill-advised and ecologically flawed attempt to increase aphid predation. It was flawed not because it did not do its job, but because it was way too successful and now has displaced native lady species to be the dominant lady beetle species in the prairies. Has its presence reduced aphid populations? There is no evidence to prove that it has. But that should have been expected in an environment where all ecological niches were occupied beforehand. 

Photo by Deborah Petrie