Plants have an immune system just like people do. The healthier the plant, the more it can fight off pests and disease, even when stressed due to heat, drought and poor soil. Inspect your garden often for early warning signs.
Plants have special chemicals that make them distasteful to bugs. When they are weakened by stress, the chemical levels are reduced and the plant becomes vulnerable. Often bugs attack the weakest plant of a group and never spread to the healthy ones because their chemicals are more concentrated. These chemicals are so effective they are extracted for botanical pesticides such as pyrethrum, which is derived from a species of chrysanthemum. For every pest in nature there is a predator bug that will leave the plant alone while dining on the bad bugs. These are called beneficials and include ladybugs, praying mantis and lacewings. Protecting beneficials takes advantage of nature's control mechanisms. Chemical pesticides kill both pests and beneficials, which leads to pest population explosions once the predators are gone. The best approach to pest control is through least toxic measures designed to protect beneficials while controlling pests.
Identify pests so you know what kind of damage potential they represent. For example, a gang of aphids can distort leaves, but they are nothing compared to a gang of armyworms that can defoliate a shrub overnight! Once a pest is identified, you can choose one of these least toxic controls:
Fungus. Most plant diseases are fungi that thrive under certain weather conditions. They often attack roses but other trees and shrubs can be afflicted as well. It may be a temporary weather-related condition or due to plants receiving too much shade.
Mildew is actually a group of white or gray powdery fungi that attack plants where moisture lingers on the leaves until late in the day. It can limit new growth on leaves. Mildew is more prevalent in damp climates, but can occur anywhere.
Black spot is the rose grower's biggest nightmare. It appears as black patches on the leaves that can live through the winter to reinfect the plant the following year. Blackspot is difficult to control and afflicts some rose varieties far more than it does others. Removing affected leaves and raking up fallen ones is essential to control. A variety of fungicides are used to control mildew and blackspot. See your garden center for options.
Controlling caterpillars is easy using nontoxic Bacillus Thuringiensis (BT). Apply to plants in either powder or liquid form. Once eaten by a caterpillar, the pest dies. However, BT is safe around both children and pets.
Monrovia plants are naturally more resistant to pests and diseases. We strive to grow plant varieties that are hardier and more pest and disease resistant. Our soil mix contains mycorrhizal microorganisms that live with roots to help plants resist debilitating problems. This benefit combined with care and attention makes our plants perform, and your garden remains as pest and disease free as possible.