1. Ornamental Pest Management (Category 3B)

    2. Pest Management Techniques

    Chapter 2

  2. Although applying a pesticide is a commonly used pest management tactic, pesticides are not the only or best way to manage all pests. Pesticides provide effective, but typically short-term suppression of pests.
  3. Since the ultimate goal of a pest management program is to establish a landscape that can by itself maintain pest populations at non-damaging levels, you must use tactics that provide long-term control. These include plant resistance, environmental modifications, cultural practices and biological controls.
  4. For example, management of a heavy infestation of Japanese beetles in a rose garden might include:
  1. Applying an insecticide to quickly reduce feeding adults (short-term suppression).
  2. Establishing milky spore disease in the lawn to limit Japanese beetle grubs.
  3. Planting rose varieties that do not bloom when beetles are feeding.
  4. Avoid planting other preferred hosts such as linden, crabapple, or Japanese maple near roses.

5. Hosts are the plants attacked by pests. The first step in discouraging pests is to assure the health and vigor of landscape plants since they are less attractive and better able to combat pests and withstand pest injury. Secondly, avoid growing plants that are prone to multiple pest problems.

6. Several factors influence plant health, and therefore the plant’s ability to resist pests. For instance:

-Plant selection. Some ornamental plants are shade-loving, while others require full sun to grow. Acid-loving plants, like rhododendrons and many oaks, are stressed when planted in soil with a high pH. Matching plant species’ growing preferences to site conditions is essential to overall plant health.

-Cultural care. Mulching, watering, pruning and other properly-implemented plant care practices help keep landscape plants healthy and vigorous.

-Environmental modification. Whenever possible, modify the growing environment to better suit established landscape plants. For example, wrapping boxwood and other broadleaf evergreens protects them from drying winter winds and road salt.
  1. Genetic makeup also plays an important role in a plant’s resistance to pest injury.

-Species. Certain species of landscape plants are susceptible to troublesome pests. Dutch elm disease hits American elms hard, but is much less serious on Chinese elm.
  1. All three of the trees pictured here are cultivars of London plane tree. Genetic variation in susceptibility to sycamore anthracnose is clearly shown by the amount of defoliation. In this photo, two sycamores are defoliated (susceptible) and the London plane tree is fully-leafed (resistant).
  2. Cultural controls can be used to create an environment more hospitable to ornamentals and less suitable to pests. Many cultural controls are easily incorporated into existing plant care activities. For instance, on wet sites proper irrigation, improved drainage, and aerating the soil are all practices that prevent plant stress due to saturated root zones. Many diseases and some insects prefer dense plants. Pruning discourages these pests by increasing light and air movement in the crowns.

    3. Sanitation is a cultural control that reduces pest habitat and inoculum by removing brush, weeds, trash, and disease-infected leaves.

  3. The spotted leaves in the slide are caused by the fungal disease black spot. Heavy infestations will defoliate roses. Management of this disease includes cultural controls – destroying infected plant parts, improving air circulation, and avoiding overhead irrigation.
  4. Mechanical and physical controls physically separate the pest from the host plant. These activities can be time-consuming, but are completely non-toxic.

    5. Hand removal of weeds may be the only practical way to manage beds where ornamentals cannot tolerate pesticide applications, Hand-picking or clipping will rid crabapple trees of Eastern tent caterpillar. The egg masses of pests like gypsy moth or pine sawfly can be removed to decrease the upcoming pest population.

    Traps provide suitable plant protection in some cases. Slugs and earwigs hide under boards which can be turned over and the pests removed. This mole trap is an example of mechanical control used to limit tunneling damage. Note: trapping wild animals may require a permit from the Michigan Department of Natural Resources.

  5. Barriers such as plastic wraps and hardware cloth tree wrap keeps deer, rabbits and mice from feeding on the bark of young trees. Sticky tape around tree trunks prevents gypsy moth caterpillars form climbing up the foliage.

    6. Repellants use noise, odor, light, vibration or taste to make the host unattractive to pests. Repellents are commonly used to discourage mice, deer and other vertebrates from feeding on landscape plants.

  6. The spider and green lacewing shown here are important predators of many landscape pests, and are examples of biological controls. The predators, parasites, and diseases are responsible for preventing widespread outbreaks of ornamental pests.

    7. 14. Predators feed on a number of pests during their life time. Parasites complete their development on a single host. Mature parasitic wasp larvae are emerging from their caterpillar host in this photo.

  7. Survival and population growth of beneficial organisms are dependent upon the availability of a food source. A pest-free landscape may support fewer biological control agents.

Biological control tactics are designed to encourage the survival of existing natural enemies or increase populations of beneficial organisms.

- Encouraging existing beneficials. In addition to the host plant, beneficial organisms require water, shelter and alternate food sources for survival.
  1. Supplement natural enemy populations.

Predator/parasite release. Many species of beneficial insects can be purchased for release into the landscape. Although the majority of released predator and parasite insects will move out of the area, the few remaining help limit pest populations.

Pathogen-based pesticides provide plant protection without endangering the environment or nontarget organisms. The most commonly used microbial insecticide is Bt(Bacillus thuringiensis). Pathogens take time to infect and destroy insect pests. So, do not expect microbial insecticides to quickly reduce populations.