Southern Chinch Bug and Weed Occurrence in St. Augustinegrass

1. 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

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

3. 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

4. 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)

6. 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

7. 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

8. 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

9. 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

10. 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

11. SCB, weeds, and St. Augustinegrass groundcover by habitat in St. Augustinegrass

12. 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

13. 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

14. 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

15. 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

16. Questions?