California Poppy Pests & Disease Problems

Aphids

• Aphids feed on the juices of the poppy plant. They use specialized mouth parts to suck fluids from the plant, which can cause curling, yellowing and distortion of leaves, as well as stunted shoots. While aphids typically won’t kill a mature plant, the honeydew they leave behind is unsightly and can lead to the development of sooty mold fungus. Nonchemical control methods are best as insecticides destroy beneficial insects along with the aphids. Natural predators of aphids include parasitic wasps, lady beetles, lacewings and syrphid flies.

Beetles

• Round holes in the petals of California poppies are an indication of a hoplia beetle (Hoplia callipyge) infestation. Adults are oval and about 1/4 inch long with a reddish brown head and a body that appears iridescent green in sunlight. The light-colored leaves of California poppies are especially attractive to these beetles. Fortunately, these pests are present for a limited time each year four to six weeks from late March to May. Picking the beetles off by hand is the best method to deal with a small infestation as effective control is difficult using insecticides.

Other Insects

• A variety of winged true bugs also infest California poppies. Similar to aphids, they suck juices from the plant, though the damage tends not to be as severe. The best management approach is to provide proper cultural care so the poppies are healthy and vigorous. Remove damaged or infested leaves or stems. Chemical sprays aren’t recommended, but you can use a ready-to-use insecticidal soap for a larger infestation. Be sure to completely cover the plants with the spray, including the underside of the leaves and petals. Because the soap only kills pests present during the spraying, you may need to apply it again.

Fungal Diseases

• Most fungal infections produces lesions and masses of spores on leaves and petals. A downy mildew infection produces reddish lesions on upper leaf surfaces and fluffy gray, tan or purple areas on the undersides. Brownish lesions and masses of gray spores indicate the presence of gray mold, while powdery mildew announces its presence through a white, powdery coating on stems, leaves and blooms. Prevention is the best control for these diseases so plant the poppies in a sunny area, water them at the base, thin them regularly to improve air circulation and don't over-fertilize. Keeping the growing area free from leaf debris and removing infected plant material as soon as possible also keeps mold and mildew at bay. The rhizoctonia root-rot fungus attacks poppies through their root systems, leaving the roots black, shriveled and soft. The best control method is proper care to keep the plant healthy, being particularly careful to avoid excess moisture in the root zone. Should any of these fungal diseases become a problem, a mixture of 2 1/2 ounces of neem oil in 2 gallons should be sprayed every seven days. Cover all parts of the plant with the spray. Check the label for dilution rates as these may vary by brand.

Viral Diseases

• Poppies infected with tomato spotted wilt virus die young or suffer from delayed blooming. Symptoms include black or yellow stem streaking, spots, line, ring or stripe patterns on flower petals, and severe leaf distortion. It can only be transmitted by thrips, tiny insects that acquire the virus as larvae and spread it as adults. The disease cannot be cured in plants so managing thrips is the only effective control. Spray neem oil to control small thrips populations and remove any plants that become infected with a virus. Dilution rates and application methods are the same as for controlling fungal diseases.