Pest Prevention in Ornamental Gardens

Here is what you can do to prevent pests in your ornamental garden:

Grow suitable plants - source disease resistant varieties (especially roses and hostas). Ask at your local nursery.

Practice garden diversity – grow a large variety of plants. Diversity also minimizes the impact a specific pest will have on the overall visual effect of your garden, since many attack only one species of plant.

Companion Plant - Planting schemes in which different species are planted close together for the benefit of one or both species. Companion plants that repel pests or attract beneficial insects need not be planted permanently, but can be grown in planters or pots and moved around to where they are needed.

Interplant - Interplanting a garden with many different species means a healthier garden, since there tends to be less competition for nutrients and moisture and provides a source of alternative diets to sustain predators and parasitoids during winter, early spring, when pests are scarce. The mixture of colors, odors, and texture confuses insects, making it more difficult for them to find their favourite food plants. Try using a mixture ofvegetables, flowers, and herbs with wild patches scattered throughout.

Common Ornamental Pests

Roses - Roses are especially vulnerable to powdery mildew and black spot. These are fungal diseases that can lay dormant in the soil. Caused by excessive moisture and water falling directly on leaves. Watering roses in the morning allows the plants leaves to dry during the course of the day. A preventative program for black spot should begin in the fall with a thorough sanitation program. Diseased leaves on the ground should be raked and burned or removed. All diseased canes should be pruned back to healthy wood. These practices will reduce the amount of overwintering fungus. Unless this is a prized rose bush, consider getting rid of it altogether and planting a more disease resistant variety – your local nursery will be able to help.

Rhododendrons – several species of weevil attack rhodos. Foliar (on the leaf) notching generally indicates adult weevil feeding, which suggests an infestation by their larvae (grubs), a serious problem that can easily escalate in your garden. Weevils are nighttime feeders, so spend the day in the loose ground, mulch or leaves beneath or near the plants. A nematode application (done correctly – see sidebar above) is the best way to rid your rhodos of these pests or you can try hand-picking the weevils at night. (Click here for more information)

(More to come on weevils and weevil damage...)