2019 Georgia southern pine beetle prediction survey report

2019 Georgia Southern Pine Beetle Prediction Survey Report
Georgia Forestry Commission Forest Health Staff

The Georgia Forestry Commission (GFC) participates annually in the southern pine beetle (SPB) prediction trapping program. Southern pine beetles are the most destructive forest pests in the southeastern states. Survey results are documented in the report so that activity and damage levels can be anticipated and mitigated.

The Georgia Forestry Commission follows the SPB Prediction Trapping protocol set up by Texas A&M. A 12-funnel Lindgren trap is baited with a three lure system: Frontalin, Sirex and the endo-brevicomin flexlure (Figure 1). Traps are placed in the field to coincide with redbud bloom (around the first of March in the southern part of the state and mid- March in the northern part of the state). The Georgia Forestry Commission placed 45 traps across the state in 38 counties and six weekly samples were collected from each trap. The number of SPB and clerid beetles (a natural predator of SPB) were counted each week.

Figure 2 shows the results from the trapping survey, classified as

overall SPB per day during the six-week trapping period. Six of

the 38 counties with traps had moderate numbers of SPB caught

during the trapping period. These include Clarke, Dawson,

Greene, Haralson, Quitman and Randolph Counties. No counties

had high numbers of beetles per day.

Figure 1: GFC Forester collecting

In 2018, the USDA Forest Service (USFS) and all southeastern

samples from a SPB trap.

state cooperators collaborated with Dartmouth College and Bates College, through the Science and

Technology Development Program, (STDP) to develop a new prediction model. They found the two

greatest factors in predicting the probability of the area having SPB spots are the number of SPB

collected per two-week period in the current year, and the number of SPB spots in that county last

year. This year is the first year GFC is using this model. The results from the 2019 survey predict that

overall SPB activity will be low across the state, with two areas of high probability of any spots

(Figure 3). Figure 3 shows the probability of a county that had a trap having any SPB spots this year.

Across the state, the probability of having any spots ranges from a 0-80%. Rabun County has this

highest probability of having any spots, at 80%. Habersham, Jasper, Jones and Putnam Counties have

the next highest probability of having any SPB spots, between 60-80%. Bartow, Chattooga, Clarke,

Dawson, Greene, Haralson, Lumpkin, Quitman and Randolph Counties have a 20-40% chance of

having SPB spots. The remaining 24 counties have less than 20% chance of having any SPB spots.

Another way to present the data are shown in Figure 4, as the probability of a county having greater than 20 SPB spots. These results show Rabun County as having an 80% chance and Habersham
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County having a 60% chance of having more than 20 spots. Perhaps a more informative prediction, because it accounts for more variability within the historical data, is the probability of greater than 50 spots in a county (Figure 5). Again, Rabun County have the highest probability of having greater than 50 spots, with a 60% chance. Jasper, Jones, Habersham and Putnam Counties have a 40% chance of having greater than 50 spots. The remaining 33 counties that were trapped in 2019 have less than 10% chance of having greater than 50 spots. To put this in perspective, over the last decade, we have only seen the total number of spots statewide rise above 50 three out of ten years.

These prediction models help guide landowners in management decisions. They do not guarantee that outbreaks will or will not occur on their property. The best advice is for landowners to manage for healthy forests with techniques such as thinning, prescribed burning and invasive species control. In the past decade, SPB outbreaks have been limited to infestations in stands that are either over-stocked or over-mature. Southern pine beetle favors pine stands that are over-crowded and stressed. The GFC will begin aerial surveys for southern pine beetle in June 2019 and additional aerial surveys will be performed throughout the year.

For additional information contact:

Chip Bates Forest Health Coordinator Georgia Forestry Commission cbates@gfc.state.ga.us

Lynne Womack Forest Health Specialist Georgia Forestry Commission lwomack@gfc.state.ga.us

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Figure 2: Southern Pine Beetle trap locations established by the Georgia Forestry Commission and the number of SPB caught per day over the six-week period.
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Figure 3: Probability of any infestations

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Figure 4: Probability of 20 or more infestations

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Figure 5: Probability of 50 or more infestations

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