Southern Chinch Bug and Weed Occurrence in St. Augustinegrass

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Southern Chinch Bug and Weed Occurrence in St.
Augustinegrass

• C. Rainbolt, R. Cherry, and R. Nagata
• Everglades REC/University of Florida-IFAS
• Belle Glade, FL

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Introduction

• St. Augustinegrass lawns are utilized throughout
  the southern United States
• Climactic and environmental adaptation
• Tolerance to sun

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Weeds in Turf

• Create visual disruptions of uniformity that
  reduce aesthetic appeal
• High plant densities can prevent weeds from
  becoming established
• Actively growing plants are more able to compete
  with weeds than weakened plants
• Biotic or abiotic conditions that weaken grass
  stands can result in increased weed populations

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Southern Chinch Bug

• Blissus insularis Barber is the most damaging
  insect pest of St. Augustinegrass
• Ability to develop resistance to insecticides and
  overcome host resistance

• Heavy infestations cause substantial damage to
  St. Augustinegrass that leading to dead brown
  patches of turf

Photo by Mr. Jim DeFilippis (www.turfgrass.com)
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Arthropods X Weeds

• Norris and Kogan (2000) published a thorough
  review of arthropod and weed interactions
• Although many relationships between arthropods
  and weeds are recognized, few are documented
• Interaction can result in habitat modification
  that favors the development of one or both
  species

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Background and Objective

• In southern Florida, weed infestations commonly
  occur in areas with southern chinch bug (SCB)
  infestations
• The objective was to determine if SCB caused
  higher weed populations in St. Augustinegrass

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Materials and Methods

• Eight sites were sampled from March to August,
  2005 in urban lawns in Palm Beach County, Florida
• Each site contained 3 distinct habitats (5 x 5 m
  each)
• Active SCB infestation
• Weedy St. Augustinegrass
• Green healthy appearing St. Augustinegrass

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Southern Chinch Bug Sampling

• Sampled by vacuuming five randomly selected 30 x
  30 cm areas for 2 min using a modified
  blower/vacuum
• Samples were frozen for later counting, thawed,
  and passed through a sieve to remove debris
• Counted by microscopic evaluation

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Weed Sampling

• Following chinch bug sampling, weeds were counted
  and recorded by genus and species within five
  randomly located 0.4 m2 subplots in each habitat
• St. Augustinegrass groundcover was estimated
  visually on a scale of 0 to 100
• Data from the eight sites were pooled and mean
  differences were determined using LSD test

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SCB, weeds, and St. Augustinegrass groundcover by
habitat in St. Augustinegrass
Habitat SCB per m2 Weeds per m2 Groundcover
SCB infested 1956 62.3 39
Weedy 13.3 164.9 13
Healthy 1.4 9.1 96
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SCB Results

• SCB populations are similar to other studies
• SCB are highly aggregated at infestations with
  few in surrounding healthy St. Augustinegrass
• Superimposing SCB and weed data shows that weeds
  were infesting areas of chinch bug damage since
  chinch bugs had little attraction to weedy
  habitats

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Weed Results

• Weed populations were higher and St. Augustine
  groundcover was lower in the SCB infested
  habitats
• 28 weed species were identified, 7 were monocots
• SCB breed exclusively on monocots
• The most commonly found species were southern
  crabgrass, common bermudagrass, small hop clover,
  Hyssop spurge, and green killinga
• Healthy sites contained an average of 3.8 2.6
  different species compared to 6.8 4.3 in weedy
  and SCB infested habitats

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Discussion

• Data did not indicate that certain weed species
  were more able than others to capitalize on SCB
  damage and become established
• The prevailing weed species in the healthy
  habitat tended to be the dominant species in
  infested and weedy habitats

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Conclusions

• When damage reduces groundcover, resources become
  available to other species that are not affected
• After SCB infestations are reduced through
  insecticidal and/or natural controls, the weed
  problem remains
• Consequently, weed suppression as a result of SCB
  should be considered when determining the
  economic threshold for control in St.
  Augustinegrass

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Questions?