From our perspective as hollyhock plants (Alcea rosea), we face numerous challenges from pests and diseases that can compromise our majestic flower spires and overall health. Understanding these adversaries from our point of view is key to maintaining a vibrant garden.
Our soft, large leaves are a prime target for sucking and chewing insects. The most frequent assailant is the Hollyhock Weevil (Rhopalapion longirostre). The adult weevils notch our leaf margins and, more critically, the females lay eggs in our developing flower buds. Their larvae then consume the seeds from within, drastically reducing our ability to reproduce. Another common foe is the Japanese Beetle (Popillia japonica), which skeletonizes our foliage, leaving us weakened and unsightly. We are also highly susceptible to infestations of Aphids (Aphidoidea), which cluster on our tender new growth and undersides of leaves, sucking our sap and excreting a sticky "honeydew" that fosters sooty mold.
Our most dreaded disease is Hollyhock Rust (Puccinia malvacearum). This fungal infection appears as orange to brown pustules on our leaf undersides, with corresponding yellow spots on the upper surfaces. It causes our leaves to wither and die prematurely, severely depleting our energy reserves. We are also vulnerable to various Leaf Spot diseases (e.g., caused by Cercospora, Colletotrichum), which manifest as brown or black spots on our foliage, leading to defoliation. In poorly drained soil, fungal pathogens like those causing Anthracnose can lead to stem cankers and root rot, attacking our very foundation.
To protect us organically, a multi-faceted approach is best. For pest control, encourage beneficial insects like ladybugs and lacewings that prey on aphids. For larger pests like Japanese beetles, hand-picking them off our leaves early in the morning and dropping them into soapy water is highly effective. Applying neem oil or insecticidal soap can help control moderate infestations of sucking insects. To manage Hollyhock Rust and other fungal issues, ensure we have excellent air circulation by spacing us appropriately and avoiding overhead watering. Remove and destroy any of our infected leaves immediately—do not compost them. Applying a preventative fungicide like sulfur or a diluted copper spray can help protect our healthy foliage. Finally, cleaning up all our plant debris at the end of the season is crucial to eliminating overwintering sites for pests and disease spores.
