IPM: Resistant Varieties

dbg_lah_6794Is your garden being bugged? While 95% of all insects are either beneficial or benign, that last 5% can eat us out of house and home—or at least out of cabbage and broccoli. If insect invaders are on the attack, sometimes you just have to fight back.

Pests may be persistent, but we gardeners are not helpless. I like to remind myself that I am smarter than an aphid and more cunning than a flea beetle. When it comes down to a battle for the harvest, there are lots of tools at our disposal. As a master gardener, I was taught the principles of Integrated Pest Management, or IPM. Rather than just reaching for a spray can, this approach is multifaceted. There are many ways to outwit a weevil.

Gardeners using an IPM strategy will first consider varietal selection and cultural control methods, realizing that the goal is management, not the annihilation of every single pest in the garden. When significant damage begins to occur, physical and biological controls are implemented. Chemicals, even organic ones, are a last resort.

The first step in maintaining a healthy garden is choosing the right varieties, or cultivars. Newer hybrids are bred for disease resistance, or at least disease tolerance. In plant species where disease has traditionally been an issue, it pays to do some research before buying a new bush or tree, or ordering seeds.

For example, cucumbers, and zucchini and other summer squash, are particularly susceptible to powdery mildew. With this in mind, breeders have come up with varieties that are tolerant to this fungal disease. That means that your plants will continue to live and produce a good harvest even if their leaves are covered with fuzzy white mildew.

Or, take tomatoes. There are an amazing number of diseases that attack tomatoes. Nematodes, Tobacco Mosaic Virus, Alternaria stem canker, and various strains of Verticillium wilt and Fusarium wilt are a few of the most common. Thankfully, breeders have developed varieties that are resistant to many of these diseases. They are marked in catalogs (and on plant labels) with initials such as VFN, or perhaps TMV. A helpful website, tomatodirt.com, offers an easy-to-understand explanation of what all the letters stand for, but in general, the more letters listed after the variety name, the healthier your plants are likely to be.

It’s sad to lose a squash harvest to disease, but losing a tree is much more costly and harder to replace. Fireblight is a bacterial disease that attacks members of the rose family, such as crab apples, pears, cotoneasters, hawthorns, pyracanthas, blackberries, raspberries, and mountain ashes. The disease is particularly prevalent along Colorado’s Front Range region.

Once a plant is infected there is no cure, so prevention is important. Many of these plants are now available as cultivars that are resistant (although not immune) to infection. Colorado State University has published a list of apple, crabapple, and pear varieties, giving their varying susceptibilities to fireblight.

In general, it’s best to check on disease resistance when buying new plants of any type.  The easiest way to solve a disease problem is to not have one in the first place. Choosing the right variety can make all the difference.

I’ll cover more aspects of IPM in the future.

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