Flower Power

cosmoIncorporating flowers in agricultural landscapes has been an area of increasing interest recently. As scientists and farmers try to find new ways to make food production more sustainable, an emergent idea has been to increase the functions (See Farm Meets Function for some WY examples!) that agricultural lands provide. One way to do this is to add diversity to the types of habitats found on agricultural lands. Planting flowers in strips or patches is one type of alternative habitat that can provide a number of functions which might include:

  • Natural pest control- by supporting natural enemies of pest insects with refuge habitat and nectar.
  • Preventing erosion – by anchoring soil that might otherwise be left fallow.
  • Improving water quality – if planted as filter strips or ditch banks, these plantings can slow the flow of water overland helping to trap soil and excess fertilizer.
  • Aesthetic value – for farms where agrotourism is an important part of their business. Because hey, they’re pretty to look at.

Our lab has been investigating the role of flowers and that first point, natural pest control.

A strip of annual flowering plants and part of our study plots at one of UW's agricultural experiment stations.

A strip of annual flowering plants and part of our study plots at one of UW’s agricultural experiment stations.

Bathyplectes curculionis - a parasitoid wasp of alfalfa weevil (Image: Bob Carlson 2009)

Bathyplectes curculionis – a parasitoid wasp of alfalfa weevil (Image: Bob Carlson 2009)

 

 

 

 

 

 

 

 

In case you didn’t catch it in How Important is Honeydew, our lab is investigating what factors might be affecting parasitism of alfalfa weevil by a tiny parasitoid wasp. These wasps lay their eggs in the alfalfa weevil larvae, those eggs then hatch, and consume the weevil (think Alien – caution, not for faint of heart). As adults these wasps rely only on sugary food sources like aphid honeydew and floral nectar. Previous studies on this wasp have shown that providing them with a food source can increase their lifespan (Jacob and Evans 2000) and also increase the time they spend searching for weevils to parasitize (Jacob and Evans 2001).

This led to one of our questions:  Will supplying these wasps with floral nectar near alfalfa fields increase the amount of weevils they parasitize?

Although we can’t answer this question quite yet, we do want to share some of our preliminary data on how the flowers performed. We tested two types of flowering habitat: a mix of annual flower species and a mix of perennials. Both groups have trade-offs and it is why we decided to compare them. Below are bloom calendars for both flower mixes. In the left column are the flower species and the green bars correspond to when they were in bloom (with the dark green showing peak bloom).

Bloom Calendar for Annual Flowering Strips

AnnualBloomCalender_2015

Bloom Calendar for Perennial Flowering Strips

PerennialBloomCalender_2015

We choose flower species for each mixture based on  whether their bloom periods would collectively span the growing season in order to best support natural enemies. One of the most emergent trends we’ve noticed so far (without getting into the insects!) is that the annual flowers don’t actually start blooming until mid July. This is a product of Wyoming’s higher altitude and later planting date and therefore a pretty important consideration for this region. The overwintering perennials on the other hand start blooming almost a month earlier. In terms of supporting our parasitoid wasp, this is a very important distinction, because this wasp is most active (parasitizing weevils!) in spring and early summer.

Stay tuned as we delve further into how natural enemies and alfalfa pests respond to these flowering habitats!

References:

Jacob, Helens S., & Edward W. Evans. “Influence of Carbohydrate Foods and Mating on Longevity of the Parasitoid Bathyplectes curculionis (Hymenoptera : Ichneumonidae).” Environmental Entomology, 29.5 (2000): 1088–1095.

Jacob, Helen S., & Edward W. Evans “Influence of Food Deprivation on Foraging Decisions of the Parasitoid Bathyplectes curculionis (Hymenoptera : Ichneumonidae ).” Annals of the Entomological Society of America, 94.4 (2001): 605–611.

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