Insect and Bird Studies

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Insect and Bird Studies on CREP Grass
Buffers Galen P. Dively Jessica Nelson
(MEES) Peter Blank (MEES) Laura Moore
(ENTM) Department of Entomology University of
Maryland
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• Grass buffers are becoming a major part of the
  agricultural landscape.
• CREP filter strips are located on 2562 contracts
  with a total of 39,084 acres (55 of all CREP
  projects).
• Additional grass habitats adjacent to cropland
  include grass strips along waterways or drainage
  ditches and along roadsides.

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• Grass buffers are becoming a major part of the
  agricultural landscape.
• CREP filter strips are located on 2562 contracts
  with a total of 39,084 acres (55 of all CREP
  projects).
• Additional grass habitats adjacent to cropland
  include grass strips along waterways or drainage
  ditches and along roadsides.

Agricultural crops are not closed systems - they
are influenced in many ways by the surrounding
landscape.
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A riparian grass buffer, or 'filter strip', is a
linear strip or area of herbaceous vegetation
situated between cropland and environmentally
sensitive areas.

• Conservation functions are
• uptake nutrients in the groundwater before they
  enter a body of water.
• filter sediments from runoff.
• spread waterflow.
• provide wildlife habitat.

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• Pest Management Questions Addressed
• Do grass buffers serve as reservoirs for insect
  pests?
• Can grass buffers be designed and managed to
  enhance conservation of natural enemy communities
  and reduce pest outbreaks?

• Wildlife Questions Addressed
• Which bird species use grass filter strips in
  the summer and winter?
• Which bird species prefer warm season grasses
  versus cool season grasses?
• How does vegetation composition, structure, and
  filter strip width affect bird use?

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• Vegetative Types of Grass Buffers
•  
• Cool season grasses
• Warm season grasses
• Which type is more sustainable for supporting
  bird and beneficial insect communities?

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Cool Season Grasses   Orchardgrass Red
fescue Hard fescue Sheep fescue Tall fescue
(non-CREP) Mix with Red clover White
clover Partridge pea
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• Cool Season Grass Buffers
• Minuses for Sustainable Pest Management
• spread quickly and form monocultures, often
  results in one predominate species.
• out-compete flowering forbs which are sources of
  food for natural enemies.
• short growth and sod-forming, so structurally
  less diverse.
• less diverse insect communities and higher risk
  of pest outbreaks.
• stressed during hot, dry conditions, which
  causes insects and mites to disperse.
• disturbed by mowing which forces pest species to
  disperse

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Warm Season Grasses   Switchgrass Eastern
gammagrass Big bluestem Little bluestem Indiangras
s Sideoats grama Broomsedge Deertongue Mixed
with legumes and flowering forbs
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• Warm Season Grass Buffers
• Pluses for Sustainable Pest Management
•  
• Evolutionary better adapted to the local
  ecology.
• Harbor less aphids and other cold-adapted pests
  than cool-season grasses.
• Require less management manipulations, thus
  fewer ecological disturbances to force insects to
  disperse.
• Structurally more diverse and more insect
  species rich.
• Growth in bunches allows room for flowering
  forbs as insectary plants.
• .

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Sampling Methods Communities w/ and w/o buffers
Comparative data with and with buffer
X
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Direct counts of insect activity
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Sampling Methods Effects of mowing
X
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Direct counts of insect activity
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Foliage- and ground-dwelling predators
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Parasitic insects
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• Influence of Grass Buffers on Natural Enemies
• Abundance of natural enemies decreases as you
  moved away from the buffer.
• During June and July, natural enemy abundance is
  greater in cool-season buffers than in
  warm-season buffers.
• In August, warm-season buffers and the adjacent
  crops have more natural enemies than cool-season
  buffers and the adjacent crops.
• The adjacent crop has a major influence on the
  types of natural enemies found in the grass
  buffers.

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Influence of Grass Buffers on Bird Use 55
species recorded
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• Influence of Grass Buffers on Bird Use
• Bird abundance and number of species are
  significantly lower in crop field edges without
  buffers than in the grass buffer types.
• No difference in bird use among buffer types
  during the summer but significantly less in cool
  season grasses during winter.
• Evidence of nesting in conservation buffers by
  13 species of birds..

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Can grass buffers be designed and managed to
enhance conservation biological control?

• Surrounding habitats can help to sustain the
  structure and function of natural enemies of
  agricultural pests by providing
• alternate food sources
• prey or hosts
• overwintering sites
• refuge from farming activities

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Beetle banks
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Increase plant biodiversity by adding flowering
forbs
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• Flowering Forbs as Insectary Plants
•  
• Which forbs are more sustainable in terms of
  enhancing beneficial insect communities and their
  ability to compete in grass buffers?
• Factors that determine the most effective
  insectary plants
• Quantity of pollen, nectar, and other food
  sources
• Time of season and day when nectar is produced
• Accessibility to floral nectaries
• Attractiveness to pollen and nectar-feeding
  insects

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Partridge pea
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• Problems in Maintaining Plant Biodiversity in
  Grass Buffers
• flowering plants are not always part of seed
  mixes.
• maintenance of biodiversity is not mandatory
  after establishment.
• orchardgrass tends to out-compete other grass
  species and flowering forbs and eventually
  dominates after a few years.
• switchgrass is also highly competitive within
  warm-season mixes, well adapted to clonal spread,
  and often takes over the stand particularly after
  controlled burns.

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• Grass Buffer Management Practices that can Help
  to Enhance Conservation Biological Control
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• increased use of warm-season grasses.
• less use of endophytic grass species.
• delay or avoid mowing cool-season grasses to
  minimize ecological disturbances.
• mow or burn partial stands each year to minimize
  disruptions.
• lightly disc warm-season grasses to turn over
  the litter layer, destroy woody growth, and
  encourage dormant grass seed and native annuals.
• re-seed flowering forbs and legumes following
  mowing or disking to help maintain plant
  diversity.

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Discussion questions Do you think grass buffers
contribute to pest problems in adjacent
crops? Can mowing be avoided or delayed in cool
season grass buffers? Are there certain
flowering forbs that are longer lasting and more
competitive in grass mixes? How do we convince
landowners to establish and maintain grass
buffers with high plant biodiversity?