When growing ornamental plants, especially perennials, there is always going to be concern whenever damage is observed, no matter how minor. In June and July a garden pest begins to make its presence known with tiny gray or brown dots scattered across the foliage of many popular garden plants. While not as ravenously destructive as the Japanese beetle, Four-lined Plant Bug (Poecilocapsus lineatus) is no less common.
Fourlined plant bugs are a mild garden pest in the sense that they are not lethal to most plants. Some tender herbs like basil can be killed by excessive damage from the piercing-sucking mouthparts of the Fourlined plant bug, but most plants only experience minor cosmetic damage. They feed on a variety of popular garden plants from tender herbs like Basil and Mint to herbaceous perennials like Liatris and Daisy, to woody ornamentals like Vibernum and Azalea.
Both the nymphs and adults of the Fourlined plant bug cause damage, but their life span of a single generation in a year means that the period of time in which they are doing damage is limited. Because they are relatively short-lived and their damage to ornamental plants is rarely fatal, it is not recommended to use pesticides to control them.
Sometimes the damage caused by Fourlined plant bug can be confused for leaf spot diseases, but this can be determined by noticing if the size of the spots changes over a few days or if they stay the same size but become more numerous. Because Fourlined plant bug damage is from their mouthparts which don't change size, they only make one size spot on the leaves where they feed. Leaf spot diseases will start as small spots that grow over the course of a few days.
If extreme damage occurs to specific plants in your garden, it can be helpful to use cultural control by cutting down those host plants in the fall and removing the foliage from your property to remove any eggs that were laid that season, thereby interrupting their lifecycle in your yard. Additionally, practicing good garden hygiene by regular weeding and debris removal will limit the hiding places for Fourlined plant bug to hang out in your garden.