Cut Flower Updates: September 12, 2025

Many chewing insects have a taste for dahlias; adult Japanese beetles, rose chafers, and Asiatic garden beetles are easy to see and can all cause ragged feeding damage on petals and flowers. Slightly less conspicuous, but occasionally problematic, are insects in the family Pentatomidae – stink bugs. These shield-shaped insects are fast-moving and good at camouflaging themselves. Some species are predatory and feed on other insects (including some cut flower pests), while others are plant eaters that may take a liking to your dahlias, like the invasive brown marmorated stink bug.

Brown marmorated stink bugs (BMSBs) were accidentally introduced to the US from East Asia and were first discovered in Allentown, PA, in 1996. They feed on a wide range of vegetable and fruit crops, flowers, and other ornamentals. These generalist herbivores are responsible for millions of dollars of crop losses each year. Many Pennsylvanians are familiar with them as noisy, buzzing household pests in winter; they can congregate indoors starting in the fall.

BMSBs generally have one generation per year in Pennsylvania, with adults emerging in late April to mid-May to mate and deposit eggs from May to August. The eggs, which are laid in clusters of 20 to 28, can often be found on the undersides of host plant leaves.

Once hatched, BMSB nymphs go through five distinct-looking stages, called instars, before becoming fully mature adults. The photo above shows a third instar nymph with a mostly black body. In addition to blossom petals, BMSB also feeds on the leaves and stems of cut flower crops.

When populations are high, cut flower growers can protect their crops from feeding damage by using light row covers. Commercially available pheromone traps can be useful for monitoring for BMSBs in the spring, though it is unclear whether they are effective at preventing crop damage during the season. In small areas, the bugs can be picked off crops and placed in a bucket with soapy water. Control with insecticides like pyrethroids, pyrethrin, and azadirachtin is most effective when earlier life stages are targeted rather than mature adults.