The heat of the summer is stressful and this year is no exception. If you planted geraniums or petunias you may have noticed the flowers have gone missing. It would be easy to blame the Japanese beetles for this because they like everything. However, this is not the case. If you take a good look at the geranium buds you may discover some holes drilled into them. If you do, your plants have fallen victim to the tobacco (geranium) budworm.
This moth comes to us from down south where it is a serious agriculture pest of tobacco and cotton. Further north where winters are colder it becomes more of an ornamental pest. Besides geraniums we see this caterpillar on petunias, and sometimes on roses and nicotiana.
Because the moth is not hardy to Nebraska our population is blown every spring either from thunderstorms or strong southern air currents. Generally we have two generations a season and sometimes in rare occurrences we can have three. Even though the budworm is not hardy to Nebraska we have seem some isolated microclimates where a small population can overwinter. Another way they survive our winters can be from storing your containers (with potting mix) in a freeze free location like a grange. Moths overwinter as a pupa in the soil about 6″ deep and die if the temperatures get below 20 degrees Fahrenheit.
When you find the flowers not opening or look ragged on petunias or geraniums most likely you have the budworm. Scout and hand pick off the caterpillars when you see them. Traditional contact insecticides will also help but regrettably Bacillus thuringiensis (Bt) will not because not enough is consumed to kill the caterpillar. Caution should be used when spraying because many beneficial insects are also drawn to the plants.
Other options would include using ivy geraniums which have shown to have some natural resistance compared to the zonal geraniums. You could also forgo geraniums and petunias all together and explore other annuals that do well here in the Omaha area.
