Butterfly Bush Diseases & Insects

Spider Mites

• Clemson State University Extension says spider mites can become an issue when butterfly bushes are stressed due to drought conditions. Unfortunately, pesticide use can kill other beneficial insects that may help keep spider mites away, so using chemicals is discouraged for this type of bush. Take measures to eliminate spider mites without drowning butterfly bushes in chemicals.

  Introduce more beneficial insects such as ladybugs to help control spider mite populations and prevent dry foots by making sure the bush stays watered. The National Gardening Association recommends watering butterfly bushes during the summer if rainfall falls below 1 inch per week. Try other natural pest control methods to keep spider mites from taking over. Garlic, chives and a handful of other herbs can repel spider mites. Look for natural products made with these ingredients.

Nematodes

• Nematodes can also invade a butterfly bush and other similar species. Clemson State University Extension says this usually happens within the sandy soils of coastal plains. You might not encounter a problem with nematodes unless you live close to the beach. You can also use natural pest control products to guard your butterfly bushes against nematodes.

Caterpillars

• Caterpillars can also eat the foliage of butterfly bushes, but usually these pests don't causes much of a problem. Eventually they bloom into butterflies that gravitate back towards the bush and perch on the flowers. Remove leaves chewed by caterpillars and take excess caterpillars out of the garden if they become a problem. You don't need to kill these pests since they are large enough for you to simply remove by hand. Take caterpillars to another location within your yard and find a new home for them somewhere else.

Downy mildew

• Diseases such as downy mildew stemming from the fungus Peronospora harioti can also invade a butterfly bush and make it more vulnerable to pests. Taking proper care of your butterfly bush can prevent downy mildew from setting in, so always make sure the soil stays healthy. Remove weeds around the bush and add 5 or more inches of compost to the soil to improve soil fertility. Prune the bush every year to prevent overgrowth and cut off any leaves with fungal infections and remove foliage that is falling apart from insects feeding on the bush. Choose fungicides that target downy mildew specifically because this type of mildew is more closely related to algae, according to Purdue University Extension. Some people might confuse powdery mildew with downy mildew, but the two types are not related.