Marin Master Gardeners
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Marin Master Gardeners

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Clean up now for a pest-free spring garden

October 12, 2018
Jane Scurich
Fall is a fabulous time for planting: the still-warm soil, decreasing daylight hours, cooling temperatures and — hopefully — the promise of rain will welcome new plants.

But, there is another important project that will help bring you healthier plants with fewer pests next spring and summer: fall garden maintenance!

UC Marin Master Gardeners love mulch and we encourage mulching at every opportunity. Mulch conserves moisture, helps protect delicate roots from sudden temperature changes, inhibits weed germination and growth, and can make the garden look really neat and tidy. But before you spread that mulch and cover the dead leaves, it’s important to remove debris from under and around plants, especially those in the camellia/rhododendron/azalea family, fuchsias and roses. Debris from these plants often contributes to spreading a variety of fungus and molds, and allowing insects to overwinter in a cozy, protected environment.

We also encourage composting as a way to reduce waste and incorporate invaluable micronutrients into your soil. But some plant material should not be added to your home compost unless you are absolutely certain it reaches 150 degrees or higher. Before spreading mulch, diligently remove fallen leaves and flowers of the above-mentioned species. Dispose of these contaminants in the trash.

The two biggest challenges I have for my roses are the rose curculio and the rose snail. At first site, the curculio (or rose weevil) may make you think you are seeing a lady bug — but don’t be deceived! On close examination, you’ll notice these bright red insects have long, curved black snouts. They feed on buds and are quite destructive. After feasting on the buds, they drop to the ground to pupate in the soil and emerge as adults in late spring to early summer. I have often been told that there is only one generation of them each year, but I continue to find rogue curculios on my roses even in September!

Rose slugs, actually a member of the sawfly family, are tiny yellow-green worm-like creatures that feed on the soft tissue of roses, sometimes completely skeletonizing the leaves. A small infestation may only create a cosmetic nuisance, but a larger population can greatly weaken the plant. These critters also pupate in the soil, so cleanup of infested leaves is critical for control.

Your annual and vegetable gardens can also be harboring overwintering spores, bacteria and disease that can contaminate next year’s plants. Remove any obviously diseased or suspicious-looking plants and vines, and do not add them to your compost. Destructive tomato hornworms, beetles and other insects overwinter in the pupa stage in plant debris, so eliminate spots for them to shelter.

While you’re in cleanup mode, take time to remove tomato cages and other plant supports. Spray them with the garden hose and allow them to dry in the sun, sanitize with a 10 percent bleach solution to more thoroughly eliminate bacteria. Scrub your garden tools similarly before storing them for the winter. I keep a container of disinfecting wipes handy to swipe my hand tools on a regular basis and help deter the spread of fungi and bacteria.

Your local nesting birds will also appreciate a clean house to return to in spring, so don’t forget to empty and disinfect birdhouses and feeders. Birds work hard all summer, feasting on insects in your garden, so welcome them back next spring with a spotless home.

Many of us continue to garden year-round in our Mediterranean climate and we rarely worry about our irrigation lines and hoses freezing, but it’s still prudent to cleanup and protect our tools and garden supports from the (hopefully) coming rain.

There’s hardly anything welcoming about a bunch of slimy, mildewed squash vines greeting us in the garden after our first drenching rains! A few hours of preventative maintenance can help avoid an unappealing mess and improve your chances for fewer pests next spring.

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