The “non- gardening” winter months are a great time to take a closer look at Integrated Pest Management (IPM) concepts and how they can be used in home gardens in the months to come. The primary arsenals used in an IPM program include natural, cultural, physical/mechanical, biological, and chemical controls. A cold, hard winter is a perfect example of a natural control, this week’s topic. As the name implies, natural controls impact pest and plant disease issues from the natural world. Gardeners don’t often get to impact these, but understanding them lends valuable insight into pest management options. Consider the following examples.
Box elder bug: Red and black coloring distinguish box elder bug from other “seed bugs” with similar life cycles. These plant feeders begin to shelter, as adults, in fall as days shorten and cool. About September, calls to the Extension office in Klamath about seed bugs and box elder bugs intensify. These insects congregate in alarmingly large numbers to warm in the sun, hiding during night and cold under siding, in crevices in and around buildings and sidewalks, and in rock walls. Clients are often disappointed by the control recommendation they recieve — a deep freeze will kill far more of these insects than any pesticide application. Pesticide may be effective during the growing season, but in fall and winter, natural control and a shop-vac are most effective. Since overwintering adults don’t feed, there’s no food plant (maples) to spray. It’s difficult to get a pesticide effectively into the cracks and crevices where they hide. Large fall congregations make these insects seem like a hazard, but the natural control of cold temperatures will leave only a few to carry on the job of repopulation the following spring.
Fruit drop: Common in stone fruits (cherry, plum, peach), this natural control also results in alarm, followed by calls to the Extension plant clinic. Observant gardeners notice partially developed fruit littering the ground under their trees, sometimes in substantial numbers. Multiple factors contribute to fruit drop, often in combination: poor pollination, unfavorable temperatures at bloom, nutrient balance, drought. Whatever the reason, the tree is no longer investing energy in a portion of the fruit, theoretically leaving more energy for remaining fruit. Careful examination of fruit may inform whether there is truly an issue. Spots, blotches, rotten places, mold might indicate a disease problem. Dissecting a few fruit might reveal small insect larvae. Underdeveloped, but otherwise healthy appearing fruit may just be the result of “nature’s cull.”
Soil solarization: Used to fight soil-borne plant disease, weed seeds and occasionally soil dwelling larvae, soil solarization uses solar power and a ground cover, usually plastic, to heat the soil and kill destructive organisms — an example of an applied natural control, manipulating the sun’s heat into a pest control tool. Results vary widely with this technique, leading some to dismiss solarization as a tool. Considering the variation in soil types, temperature, climate, plastic, and the variety or organisms the attempt is supposed to control, it should not be at all surprising that this technique can be tricky. Recent research from Oregon State University, just released, highlights one of the more promising applications of this technique: bit.ly/36UnKgi.
Natural enemies: The concept of an interdependent “food web,” in which change along any one species “strand” affects other species to varying degrees, can be understood on infinite levels. Most environmentally conscious gardeners are well aware of the value of natural enemies in the garden, those insects, birds, bats, and other creatures that eat the insects eating our plants. Knowing which species of predatory mite to release, at which temperature, per square foot of greenhouse space, dependent on the growth stage of the plant, is understanding that web on a completely different level. We’ll look more closely at utilizing predatory insects in the garden in an upcoming column when we categorize them as “biological controls.” For now, consider that a diverse landscape supports more members of that food web, contributing to a more balanced garden “ecosystem.”
Natural products vs. natural controls: The term “natural” is appealing in relation to gardening and pest control products, but has no regulated definition relative to product branding. Organic pesticides must be derived from natural rather than synthetic ingredients, but they are still designed to kill pests, regardless their natural status. Arsenic is a natural and very effective pesticide, but has no place in an organic, or any other, garden application. In IPM, “natural controls” are usually not products: they are things like temperature, moisture, and geographic features that impact plant-pest relationships. We’ll take a look at some of the many products that might be implemented in an IPM program in the following weeks as we examine the other arsenals: cultural, mechanical/ physical, biological, and chemical.
Nicole Sanchez is horticulture faculty at OSU’s Klamath Basin Research and Extension Center. For more information on this or other gardening topics, contact Sanchez at 541-883-7131 or Nicole.firstname.lastname@example.org, or attend a “Garden Gab” session at Leap of Taste, fourth Friday of each month, 8:30 to 9:30 a.m.