How do management strategies change pest and natural enemy populations within agroecosystems?

Natural enemies can provide meaningful population control of pest insects within agroecosystems. But within intensive agricultural habitats, natural enemy populations are often diminished due to lack of appropriate habitat and chemical pest management programs. This project compares management strategies on different commercial blueberry farms with varying levels of habitat enhancements (such as wildflower plantings) and chemical management (conventional versus organic versus no-spray farms) to monitor natural enemy abundance and activity. I am particularly interested in natural enemy activity in regards to the most economically important pest for highbush blueberry in Michigan, spotted wing drosophila, Drosophila suzukii (SWD). Ground predators of SWD pupae, such as spiders, crickets, and ants, are being monitored, as well as removal rates of SWD pupae under different pest management regimes. I am also monitoring populations of SWD to see if certain management programs lead to elevated pest pressure, as there has been some concern that SWD populations can build up in natural areas, and habitat enhancements (such as wildflower plantings). The dynamics of pest and natural enemy populations under different management programs is therefore important to work out in order to make recommendations for sustainable integrated pest management programs. 

 

This project is funded by my USDA NIFA postdoctoral fellowship.

Wildflower plantings: Oasis, or pesticide trap?

Pollinators are essential for optimizing yields of specialty crops such as blueberry. Both managed honey bees and wild bees provide this service by visiting crop flowers and transferring pollen between plants, which eventually leads to fruit. Wild bees are particularly efficient at moving pollen, which is one reason growers have increasingly been trying to attract wild bees to their farm. One way to do this is to put in pollinator habitat. In blueberry, this often means a small parcel of land adjacent to the crop is seeded with wildflowers attractive to wild bees. And presence of these plantings has been shown to increase wild bee diversity and abundance. However, the proximity of these wildflower plantings to active pest management (pesticide sprays) could put bees at risk of increased pesticide exposure. In this project, I will determine if presence of these plantings on farms leads to elevated pesticide exposure, and where on the farm pesticide exposure is the highest (wildflower plantings, weeds adjacent to the crop, etc.). Finally, I will be testing some strategies growers can use to decrease pesticide residues in wildflower plantings, such as use of drift reduction technology, or changing the placement of these plantings.

 

 

 

 

 

 

 

 

 

 

 

This project is funded by my USDA NIFA postdoctoral fellowship.

Managing pests during bloom while supporting healthy pollinators

Managing crop pests during the bloom of bee-pollinated crops, such as blueberry, can be particularly challenging. Growers must strike a balance between effective suppression of pests, and limiting risks to pollinators. This project will better understand the risks pesticides pose to managed bees during blueberry bloom, and test strategies for mitigating these risks. 

Pesticide exposure - The project will identify and quantify pesticides found in bee collected pollen from managed bumble bees (Bombus impatiens) and honey bees (Apis mellifera) brought into blueberry fields for pollination. We will also identify the source of the pollen (what plants the bees are visiting). This will help us determine if managed bees are being exposed to pesticides through pollen and if so, where exposure is coming from. 

 

Disease risks - Beekeepers often find that their hives have elevated rates of European foulbrood (EFB) disease after blueberry pollination. Therefore, we are testing strategies for reducing EFB rates in honey bees by exploring some of the potential stressors that could be leading to high rates of infection, such as poor nutrition, and pesticide exposure. We are also testing beekeeper strategies for mitigating these stressors. 

 

Best management practices - Finally, we are testing grower best management practices, such as night spraying and use of drift reduction technology, to reduce risk to bees while suppressing pest populations. 

 

This project is funded by Project GREEEN, the MIchigan Blueberry Commission, the Michigan Beekeepers Association, and the North Central Integrated Pest Management Center. 

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Identifying recent changes in bee diversity and abundance in Michigan blueberry fields

Highbush blueberry is pollinated both by managed bees (mostly honey bees) and wild bees. In fact, wild bees account for between 10-80% of pollination provided to highbush blueberry in Michigan. 

But there have been recent concerns about declines in wild bee populations around the world. Given that wild bees are so important for this crop, we wanted to evaluate changes in wild bees in blueberry fields over time. Therefore, we are comparing the diversity and abundance of wild bees found in blueberry fields over a 14 year period (2004-2018), using consistent repeated sampling methods. 

 

This project is part of the Great Lakes Pollinator Health project and is funded by the USDA-NIFA.

Comparing current Michigan bee diversity to historic diversity

Very little is known about the current status and trends of most wild bees. Therefore, using museum specimens, and contemporary collections, we are comparing current wild bee diversity to historic rates around the state of Michigan.

 

This project is part of the Great Lakes Pollinator Health project and is funded by the USDA-NIFA.

Impact of pollinator plantings on the health of alternative managed pollinators 

Alternative managed pollinators, such as leaf-cutter bees (Megachile) and bumble bees (B. impatiens), have increased in use for pollination of specialty crops. It's thought that one way to support these alternative pollinators is to provide them with a wider diversity of flowering plants. One way to do this is by establishing wildflower plantings adjacent to crop fields. This project will test if presence of pollinator plantings adjacent to blueberry and cherry fields improves the health of these target pollinators.  

 

This project is part of the Great Lakes Pollinator Health project and is funded by the USDA-NIFA.

Connect with Dr. Graham

kelsey.katherine.graham(at)gmail.com

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Air-blast sprayer applying pesticides (Photography by Gregory Heath)