CHAMBERSBURG, Pa. — Producers of grain and forage crops are well acquainted with a myriad of pestiferous ‘bugs’ (invertebrates); which, at high population densities, often reduce yields directly through feeding damage or indirectly through pathogen transmission. These pestiferous bugs require management considerations like crop rotation, or the use of insecticidal seed treatments and foliar applications. Fortunately, there are many beneficial bugs that reside in crop fields that assist us with regulating pest populations.
Beneficial bugs that consume pestiferous bugs are called natural enemies. They generally help us by acting as predators or parasitoids. Beneficial bugs that are predatory consume pest eggs, juveniles, and adults. Common predatory bugs include ladybugs (juveniles and adults), lacewings (juveniles), ground beetles (juvenile and adults), rove beetles (juveniles and adults), spiders, and mites. Beneficial bugs that act as parasitoids lay their egg(s) on a pest host, the egg(s) then hatch and make their way into the host’s body. These parasitoids live off of the host’s resources eventually causing their death. The parasitoids will emerge from the host and complete the next portion of their life cycle as free-bodied bugs. Parasitoids are typically smaller than predatory bugs, thus a little more difficult to spot in the field. There are many species of flies and wasps that act as parasitoids.
Predators and parasitoids remove individuals from the population, lowering the population density and often protecting crop yields. These benefits are worth protecting and there are a few things that producers can do to preserve beneficial bugs and promote their existence.
- Scout fields. Many pestiferous bugs in Pennsylvania are sporadic, and do not regularly cause economic damage. Monitor pest populations by randomly sampling with an insect net and by visible inspection throughout the field. Pestiferous bugs often cause unique damage when foliar feeding with chewing mouthparts. Monitoring populations and plant damage can guide our management.
- Work off of economic thresholds when using insecticide applications. Applications should be made when the return on investment from crop protection exceeds the cost of control. Insecticides applied to control pestiferous bugs often impact beneficial bug populations. Judicious use of insecticides preserves natural enemies and delays the development of insecticide resistance.
- Increasing plant diversity generally increases beneficial bug populations; consider crop rotations and cover crop mixes that can help meet the needs of beneficial bugs. Diverse cover crop mixes often provide beneficial bugs an important overwintering habitat, as well as alternative sources of nectar and food.
In addition to beneficial bugs, there are many pathogens that impact pestiferous bugs directly. Often fungal pathogens can limit populations of pestiferous bugs below economically damaging levels.
Just as we are able to monitor pest populations, we can monitor populations of beneficial bugs in our fields. It is helpful to have an insect net to sweep in the crop canopy; the contents can be emptied and sealed in a plastic bag for closer examination. Many beneficial bugs will escape handling, so the bag approach can allow for successful capture. Another option targeting ground-dwelling beneficial bugs includes the use of ‘pitfall traps’. I make my pitfall traps out of a glass jar and fill it ¾ with soapy water. I dig a space for the jar below the soil surface and place it flush within the ground. Making sure that no soil is collecting in lumps near the open jar lid will assist with collecting more beneficials. Check the pitfall traps 24-48 hours after deployment. Colorful flags and markers are useful to remind us of the location of our traps in the field.
If you need assistance identifying pestiferous or beneficial bugs in your grain or forage fields, contact your local extension educator. They can also assist with integrating pest management efforts and preserving natural enemies. Brittany Clark, located in Franklin County, can be reached at 717-263-9226 or by email at email@example.com.
–Brittany Clark, Penn State Extension