Hi, a Sassafraz tree from the ravine next door has seeded itself in our lawn and we’re trying to nurture it to full height. It gets plenty of sun in the location it’s in. However beetles are eating the leaves. I sprayed with End All insecticide yesterday, only to find 3 beetles on a leaf today. Please help!
It appears your young Sassafras tree (Sassafras albidum) is under attack from Japanese beetles, a known pest of Sassafraz and other broad leaf plants and trees. Japanese beetles love hot dry weather, so this summer has provided optimal conditions. Your young tree is vulnerable to these pests, as they can skeletonize the leaves of a small plant very quickly.
Japanese beetles lay their eggs in the soil under lawns. The larvae will overwinter in the soil and continue feeding as the weather warms in the spring. Once the larvae are full grown, they will pupate and emerge as adults in late June and early July. The adult beetle will continue to feed on foliage through July and August.
Your control strategy should be multi-pronged. Adult beetles emit a pheromone that helps them find each other. Getting rid of the adults can slow your infestation. Since your plant is small, you can hand-pick the beetles in the early morning when they are a bit slow and drowsy, drowning them in a bucket of soapy water.
Remember, if you live in Ontario, there is a pesticide ban for cosmetic use. Be sure any pesticide you use is compliant with Ontario’s regulations. You can find out more details on Ontario’s pesticide ban here. Any allowable pesticides you do choose to use should be applied every two or three days directly on the beetles to be effective. Remember that even pesticides allowed under the ban can be harmful to pollinators such as bees, so be judicious with your use of any type of pesticide.
You can also try to prevent an infestation next year by treating your lawn for larvae. You can apply beneficial nematodes to your lawn in late summer. Nematodes are a type of roundworm that feeds on grubs. Be sure to select a type of nematode specific to the larvae of Japanese beetles, and to apply as per manufacturer’s instructions.
There are also pheromone traps that will attract adult beetles. However, there is always a risk that these traps will attract more beetles from surrounding areas to your yard. They are most effective in large yards where you can direct the beetles far away from your plants.