SPB Outlook For 1998: Declining in Most Southern States

SPB Update. June 1998. USDA Forest Service, Forest Insect Research Project,
Southern Research Station, Pineville, LA and the Southern Region, Forest Health Protection Unit, Atlanta, GA.

Results of the annual pheromone trapping survey to forecast trends for SPB activity in 1998 indicate a continued decline in SPB population levels from the high SPB levels experienced across the South in 1995. The summary of the southwide trap program which appears on the back page, provides trap catch data for 1997 and 1998. Trend forecast for 1998 for all locations within the 13 southern states appear on the next 2 pages. Note that a number of new locations have been added in several states, especially North Carolina and Georgia.

Based on the early season pheromone survey, SPB activity in 1998 is expected to increase substantially from, the 1997 levels in only a few locations across the South. These include portions of Louisiana (St. Tammany and East Feliciana Parishes), Alabama (Lowndes and Tallapoosa Counties), Georgia (Liberty, Bryan, and Stewart Counties and Oconee RD), and Florida (Suwannee County). In general, SPB infestations are expected to decline to low levels in most other locations surveyed.

Each spring, traps baited with the SPB attractant ``frontalin" and southern pine turpentine are set out in pine forests when dogwoods begin to bloom. The traps are monitored for 4-6 weeks by federal and state cooperators. Dogwood bloom marks the primary dispersal season for populations of the destructive SPB as well as certain beneficial insects. Of particular value for forecasting purposes are catches of clerids (also known as checkered beetles), known predators of SPB. Using data on the average number of SPB captured per trap per day and relative proportion of SPB to clerid beetles, infestation trends for the current year can be forecast.

In general, average trap catches that exceed 30 SPB per day, especially those in which SPB make up more than 35% of the total catch (of SPB and clerids), are indicative of increasing or continued high SPB infestation levels in the current year. Conversely, when catches of predators far outnumber those of SPB and fewer than 20 SPB adults are caught per day, infestation trends are likely to decline or remain at low levels. For example, 1997, when SPB populations declined across the south, and average of three clerids were caught for every SPB in twelve southern states. In 1998, clerids outnumbered SPB by nearly four to one for all traps catches combined, indicating that even lower SPB infestation levels could be expected in most states. It is uncertain whether the predator population is directly responsible for declines in SPB outbreaks. Most likely, predators are just one of many contributing factors.

This survey system, developed by the Texas Forest Service, has been in use across the South since 1986. Collectively, trend predictions from numerous specific locations provide insight into SPB population shifts within a given state as well as across the South. Comparison of trapping results for the current year with those from the previous year for the same localities provides additional insight into SPB population changes. For additional information contact: Bill Upton or Dr. Ron Billings, Texas Forest Service (409) 639-8170.