Essential tips for managing fall weed and insect pests

Q: Which fall or overwintering weed and insect pests do nursery growers often struggle with?

Kyle Miller: The one weed that wreaks havoc is hairy bittercress. Even though it is a winter annual, it almost seems like it’s present most of the year. It is important to make sure that the preemergent applications growers are applying are particularly good on that weed, and that their reapplication intervals during the year are nice and tight. Don’t skip an application to save money because it will come back to haunt you.

Jen Browning: When we don’t get a cold enough winter or if growers carry over stock, have multi-year crops, or keep parent stock on site, these are all ways insect and mite pests can overwinter. We recommend dormant applications like Ultra-Pure®Oil horticultural insecticide, miticide and fungicide, cleaning up debris that harbors insects, mites and pathogens immediately after pruning, and putting plants to bed for the winter as clean as possible.

This includes:

1. fall clean up applications of insecticides/miticides and fungicides;
2. making sure stool beds/sheds or wintering areas are clean, temperature controlled and closed off to entry from arthropods and rodents;
3. checking stored plants during the winter and as spring approaches for temperature increases and outbreaks.

Q: When should nurseries apply herbicides and insecticides for optimal benefit to protect against pressure in the fall and overwintering pests?

KM: With herbicides, don’t let your guard down. During the “season” if you will, preemergents should be applied every eight to 10 weeks, depending on your growing conditions. We want to stay out in front of weed pressure.

JB: Insecticides are crop and region dependent on pest pressure. Not every operation or ornamental will need it. Some growers choose Ultra-Pure Oil while foliage is on plants to knock down all stages of any insects and mites on contact. Some will make a broad-spectrum fungicide application like Orkestra® Intrinsic®brand fungicide around the end of the season to prevent or reduce disease the following spring on woodies. Our objective is to get plants as clean as possible right before storage, with the hope that if they are outdoors, the cold will take care of the rest.

Q: What is one weed management practice that provides the biggest fall ROI?

KM: Don’t skip out on that fall preemergent application. While the weed pressure may seem low, soil temperatures in the fall still allow for germination of many winter annual weeds. In addition, warm spells during winter and early spring can result in additional weed germination and problems for growers. When you put down a preemergent herbicide, it must be before the weed seed germinates.

Q: What should ornamental growers do in the next 60 days to reduce spring insect pressure?

JB: Get as clean as possible. Insect and mite-wise right now: scale, mites, adult beetles and weevils are making next year’s crop of pests as we speak. Are you seeing adults? They could be laying eggs in your crop that are about to overwinter if it’s not sold this fall.

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