Armyworms are a common pest in the Midwest, and while there are several species that can be found, their presence and economic infestation levels can vary from year to year. In my experience as an entomologist, I have observed that armyworm infestations do not occur on an annual basis, but rather in sporadic outbreaks.
The life cycle of armyworms consists of several stages, including egg, larva, pupa, and adult. The adult moths lay their eggs on vegetation, such as grasses and crops, and these eggs hatch into larvae, commonly known as armyworms. These larvae then feed on the host plants, causing damage to the foliage.
The population dynamics of armyworms are influenced by various factors, including weather conditions, availability of suitable host plants, and natural enemies. Each year, the environmental conditions can vary, affecting the survival and development of armyworm populations. For example, dry and hot weather can limit the availability of host plants, leading to lower populations of armyworms. Conversely, favorable weather conditions, such as mild temperatures and abundant rainfall, can promote the growth and reproduction of armyworms, potentially resulting in higher infestation levels.
Crop rotation and the use of insecticides can help manage armyworm populations, but these strategies may not be necessary every year. In some years, the presence of natural enemies, such as parasitic wasps and predators like birds, can help keep armyworm populations in check without the need for extensive control measures.
I have witnessed years where armyworm infestations were minimal or even absent, with only a few isolated cases reported. However, there have also been years when armyworm outbreaks occurred, causing significant damage to crops and requiring farmers to take action to protect their fields.
It is important for farmers and agricultural professionals to stay vigilant and monitor for the presence of armyworms, especially during periods when conditions are favorable for their development. By regularly scouting fields and implementing integrated pest management practices, farmers can effectively manage armyworm populations when they do occur.
To summarize, while there are several species of armyworms present in the Midwest, economic infestations do not occur every year. The population dynamics of armyworms are influenced by various factors, and their presence can be sporadic. Monitoring, integrated pest management, and awareness of environmental conditions are key to effectively managing armyworm populations when they do arise.