- Agronomic: potatoes
- Additional Plants: native plants
- Animals: bees
- Crop Production: pollination, pollinator habitat, pollinator health
- Education and Training: extension, on-farm/ranch research
- Natural Resources/Environment: biodiversity, habitat enhancement
- Pest Management: biological control, integrated pest management
- Production Systems: agroecosystems, holistic management
As human populations continue to increase, it is imperative that we develop agricultural production that efficiently utilizes natural resources and ecosystem services. Insects can provide many ecosystem services to agriculture, ranging from pollination to pest suppression, and can be promoted by providing floral resources in the margins of crop fields. However, the effects that these floral plantings have on beneficial insects are not well understood, especially in conventionally managed agroecosystems. Additionally, there is little research on how well commercially available floral plantings establish on-farm, and if they also provide resources for undesired herbivores.
Working with RD Offutt, a large potato grower based in Minnesota, we compared how floral plantings in the margins of conventionally managed potato fields affected pollinator and predator abundance, as well as biological control of Colorado potato beetle (CPB). We also assessed how well floral plantings established, and what impact they had on herbivores. Using sweep net sampling, pollinator transects, and passive trapping, the abundance of various arthropods was measured both in the margins and in adjacent potato fields. Sentinel prey in the form of CPB egg masses were used to determine the level of predation on CPB. We quantified how well floral plantings established by measuring floral species richness and the amount of floral cover in the margins of fields. Field work took place from 2017-2019.
Floral plantings led to significant increases in floral cover and floral species richness compared to unmanaged margins, although there was significant variation between margins. Floral plantings significantly increased pollinator abundance in field margins. Greater floral cover and floral richness were also strongly correlated with increased pollinator abundance. Predator abundance was increased by the presence of floral plantings, but not affected by increasing floral cover. This indicates that while predators benefit from the plantings, it is not due to the increased presence of flowers per se. Within nearby potato fields, floral plantings did not increase the abundance of pollinators or predators, and may act to concentrate beneficial insects more than exporting them to surrounding crops. Sentinel prey egg masses in floral margins were preyed upon more than egg masses in control margins, but the effect was not significant. Egg masses placed in the crop were preyed upon to a much less degree, and the presence of flowers had no impact on predation rate. The abundance of herbivores was unaffected by the presence of floral plantings, either in field margins or in nearby potato fields.
Our results indicate that floral plantings can promote pollinators and predators in commercial agricultural settings, and that floral plantings do provide increased floral cover and richness without promoting herbivores. However, the beneficial effects of floral plantings may not extend into adjacent crops. Floral plantings of this kind appear to function well as a conservation tool by significantly increasing the abundance of many insect taxa in agroecosystems.
Our overall goals are to determine if floral plantings provide services to growers by: 1) Creating margins with a greater abundance and variety of flowers, 2) Conserving pollinators in agroecosystems, 3) Conserving predators and increasing the predation of key pests in adjacent fields, and 4) Not providing a refuge for pest insects or leading to greater number of herbivores harmful to adjacent crops
Objective 1: Determine how well floral plantings on the margins of agricultural fields establish after planting, and if they result in a greater richness of flower species and a larger area covered by blooms throughout the season. This will allow us to measure if floral plantings actually provide an increase in floral resources, or if growers might be wasting their money on floral plantings that provide no tangible change from margins that are unmanaged.
We will test this objective by conducting floral transects to determine number of flower species present and to quantify the amount of area taken up by blooming flowers (this is a way to quantify both abundance and size of flowers simultaneously). Agricultural margins with and without floral plantings will be compared to assess if floral plantings really do provide additional floral richness and cover.
Objective 2: Determine how floral plantings impact pollinator communities in the margins and in adjacent fields. This will allow to quantify if floral plantings are effectively conserving a greater number or variety of pollinators in agroecosystems.
This objective will be tested by conducting pollinator transects, trapping pollinators with bee bowls, and collecting pollinators from sweep net and pitfall trap samples. The abundance and community composition of pollinators will be compared between margins with and without floral plantings. Additionally, the abundance and community of pollinators in fields adjacent to margins with and without floral plantings will be compared to determine if pollinators are moving into the crops.
Objective 3: Determine how floral plantings affect predator communities and biological control of Colorado potato beetle, the main pest of concern in potato fields. This will help us measure if floral plantings provide an additional ecosystem service by increasing the predation of key pests in fields adjacent to the plantings.
This objective will be tested by collecting predators via sweep net and pitfall trap sampling. The abundance and community composition of the predators will be compared between margins with and without floral plantings, and in the potato crops adjacent to the floral plantings or to unmanaged margins. Additionally, we will place Colorado potato beetle egg masses in the margins themselves, and at the edge of the crop. The number of eggs missing or damaged over a 24 hr period will be compared between floral and unmanaged margins. This will allow us to more directly quantify predation of Colorado potato beetle.
Objective 4: Determine how floral plantings affect herbivore communities in the margins and in adjacent fields. This will allow us to determine if floral plantings are providing an ecosystem disservice by attracting or harboring a greater number or variety of herbivorous or pest insects.
To test this objective, we will use sweep net and pitfall sampling to compare the abundance and community composition of herbivores between margins with and without floral plantings, and in potato crops adjacent to the floral plantings or unmanaged margins.