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Southern Pine Beetle
2006 Southern Pine Beetle Forecast for Florida
The 2006 Florida survey was conducted using one or two traps (Lindgren funnel traps baited with turpentine and the primary SPB aggregation pheromone frontalin) in each of 25 counties (or paired-counties), with each trap located in a different stand of susceptible forest type. The 25 counties or county-pairs surveyed included those that are most likely to experience SPB problems based on historical outbreaks and/or their relative abundance of loblolly pines.
As in previous years, an effort was made to place traps in stands containing sawtimber size loblolly pine or areas where loblolly pine is most abundant. Traps were distanced at least 40 feet from any pine tree and checked weekly by DOF foresters through the month of March. Numbers of SPBs and their clerid beetle predators (Thanasimus dubius) are counted for each of the four weekly collections per trap. Numbers of SPB/trap/day and the %SPB (= [no. of SPBs x 100]/[no. of SPBs + clerids]) are then applied to the Modified SPB Prediction Chart model (Ron Billings, Texas Forest Service) to provide a forecasted level of SPB activity for the remainder of the year. Forecasted activity is based on a relative scale of Low, Moderate, High, or Outbreak.
2006 Trapping Results and Discussion
The 2006 results suggest that SPB populations remain at low levels in all surveyed counties across northern Florida. Of the 32 traps deployed statewide, none caught sufficient numbers of SPBs to warrant predictions above a “low” level of SPB activity for the coming year (Fig. 1). This year also saw an overall decrease in the %SPB statistic compared to last year’s data (Table 1). The %SPB is an expression of the number of SPBs relative to the number of clerid predators; “50% SPB” would indicate equal numbers of SPBs and clerids trapped. After increasing in 2005, this figure generally decreased or was stable in nearly all counties for 2006. This change reflects both a decrease in the number of SPBs caught and a marked increase in the number of clerids, particularly in those counties (Duval, Gadsden, and Okaloosa) which received “moderate” to “outbreak” forecasts for 2005. These data may indicate a beneficial shift in the predator-prey population balance.
One other item of interest is the overall increase in the %SPB statistic compared to last year’s data (Table 1). The %SPB is an expression of the number of SPBs relative to the number of clerid predators; “50% SPB” would indicate equal numbers of SPBs and clerids trapped. In 2005, there was a substantial increase in %SPB in about half of the counties surveyed, primarily reflecting an overall decline in clerid catch from the preceding year. Thus, although SPB populations are low and have remained static across most of northern Florida, these data may indicate a shift in the predator-prey population balance.
As in previous years, all counties in DOF Districts/Centers 1-12 will soon be asked to conduct an initial aerial SPB detection survey. Procedural guidelines for aerial surveys, ground checking, and reporting are available to Division of Forestry foresters. Confirmed SPB spots should be controlled as quickly as possible, preferably through cut-and-remove techniques. See links to SPB control information.
Because of limited survey inputs, a vast resource of potential habitat, and the limitations of the predictive model, the forecast presented here cannot be expected to be 100% accurate. Low/Static SPB predictions do not guarantee that troublesome infestations will not develop on a local or limited basis in some counties. Activity predictions are likely to be more accurate for the 5-mile radius region around each trap than for the county as a whole, and the number of traps per county (or paired-count) was reduced from three in previous years to one or two in 2006. Given the limitations of the forecast and the potential for environmental conditions to change after the survey, areas of suspicious pine mortality should be promptly inspected for evidence of SPB in the coming months.
Sincere thanks to all the foresters who were involved in installing traps, making weekly collections, and submitting jars for sample processing.
Authors: Jeffrey Eickwort, Forester, and Bud Mayfield, Forest Entomologist
Florida DACS Division of Forestry
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