Transcript Slide 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 Introduction ► St. Augustinegrass lawns are utilized throughout the southern United States ► Climactic and environmental adaptation ► Tolerance to sun 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 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) 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 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 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 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 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 SCB, weeds, and St. Augustinegrass groundcover by habitat in St. Augustinegrass Habitat SCB per m2 Weeds per Groundcover m2 % SCB infested 1956 62.3 39 Weedy 13.3 164.9 13 Healthy 1.4 9.1 96 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 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 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 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 Questions?