United States

Department of

Agriculture Fusiform-Rust-Hazard Maps

Forest Service

0

‘cD4s *

Southeastern Forest

Experiment Station

for Loblolly and Slash Pines

Robert L. Anderson, Thomas C. McCartney,

Noel D. Cost, Hugh Devine, and Martin Botkinl

Research Note

SE-351

December 1988

ABSTRACT

Rust-hazard saps made from Forest Inventory and

Analysis plot data show that fusiform rust on slash

pine is most common in north-central Florida, in

southeastern Georgia, and in areas north of slash

pine's natural range. On loblolly pine, the disease

is most common in centbal and southeastern Qeorgia and

in portions of South Carolina. These maps show the

general distribution of the disease over large areas

sad should not be used to evaluate hazard on specific

sites.

Keywords: Pinus taeda, Pinus elliottii, Cronartius

ouercuum.

Fusiform rust, caused by Cronartium

quercuum (Berk.) Miyabe ex Shirai f. sp.

fusiforme, is native to the Southeastern

United States but was not considered to

be a major problem prior to 1930.

Shortly thereafter, its significance

began to grow, along with intensification of cultural practices, especially

pine planting, and increased occurrence

of its alternate host (oak) (Dinus and

Schmidt 1977). Now, fusiform rust is by

far the most important tree disease in

the Southern United States. Southwide,

13.8 million acres of pine forest are

estimated to have 10 percent or more of

the trees infected on or near main

stems. About 2.5 million acres--6

'Anderson and McCartney are Supervisory Plant

Pathologist and Technician, respectively, USDA Forest

Service, Southern Region, Asheville, NC: Cost is

Resource Analyst, USDA Forest Service, Southeastern

Forest Experiment Station, Aeheville. NC: aad Devine

and Botkin are, respectively, Professor end

Instructor, North Carolina State University, Raleigh,

NC.

percent of the slash (Pinus elliottii

Engelm.) and loblolly (El. taeda L.) pine

acreage--are estimated to have over 50

percent of the. trees infected (Anderson

and others 1981). Stem infections in

pines less than 5 years old are likely

to kill the tree (Campbell 1965). Stem

infections contracted after age 5

usually do not kill a tree but often

cause breakage during storms or quality

loss at harvest.

Phelps (1973) surveyed plantations

across the South-and delineated areas of

rust hazard for planted loblolly and

slash pines. Squillace (1976) used

Phelps' data plus supplemental data to

develop isogram maps southwide, showing

geographic variation patterns. While

there has been interest in making

another survey like Phelps', the work

would be costly and the results would be

questionable. Many plantations now contain genetically resistant stock, and

low infection in these plantings would

confound efforts to delineate areas of

high rust hazard.

Forest Inventory and Analysis (FIA)

(USDA Forest Service) crews have been

collecting disease occurrence data for

several years, and Powers and others

(1975) used FIA disease occurrence data

to estimate the losses caused by fusiform rust in the South. They estimated

the annual loss at $28 million per year

for the entire South. Since then, the

values of products have changed, and

incidence of the disease appears to have
increased. Anderson and others (1986)

estimated annual losses at $35,227,000

in the States of Virginia, North and

South Carolina, Georgia, and Florida,

FIA data include species, percentage of

rust, and age, by location. We decided

to see if these data could be used to

construct hazard maps, instead of going

back to the field and examining separate

plots. This report presents the results

of that effort.

Methods

The forest resources in each Southeastern State are resurveyed by FIA at

approximately 6- to lo-year intervals.

During these inventories, FIA crews from

the Southeastern Forest Experiment Station record occurrence of fusiform rust

on loblolly and slash pines on permanent

inventory plots. Each State has several

thousand ground sample locations systematically distributed on its forest land.

A lo-point cluster of plots is established at each of these sample locations, and variable radius plots are

delineated with a prism with a basal

factor of 37.5 ft*/acre at five of

these points. Trees less than 5 inches

d.b.h. are tallied on fixed-radius plots

around the five sampling points. A pine

1 inch or.larger in diameter is considered infected if it has a gall on the

main stem or on a living branch within

12 inches of the main stem. These galls

are potentially lethal, especially if

infection occurred prior to age 5.

Details of the data collection process

can be found in "Field Instructions for

the Southeast, 1982” (USDA Forest

Service 1982). Additional information

is available in a paper by Jacobiand

others (1981).

The analysis was confined to FIA

plots in the loblolly and slash pine

forest types. For a plot to qualify, at

least half its basal area had to be pine

of these species. For these plots, the

following useful data were available:

l State

l Survey Unit

l County

l Location

l Forest type: slash - 1;

loblolly - 2

l Stand origin (planted or natural)

l Site class (l-5)

l Stand age (nearest year)

l Number of trees 1 inch d.b.h. and

larger of all species per acre

(nearest lo/acre)

l Number of infected pines 1 inch

d.b.h. and larger per acre

(nearest lo/acre)

l Basal area per acre of infected pines

(nearest ft*)

. Number of healthy pines 1 inch d.b.h.

and larger per acre

(nearest lo/acre)

l Basal area per acre of healthy pines

(nearest ft*)

l Basal area per acre of all species

(nearest ft*)

l Volume expansion factor

l Number of trees per acre in the 2-

and b-inch diameter classes

(nearest lo/acre)

With-the use of these FIA data,

hazard maps were constructed. Data for

the maps came from the fourth surveys of

Virginia (1977), South Carolina (1988),

and North Carolina (1974) and from the

fifth surveys of Georgia and Florida.

Data for the maps were checked manually

from computer printouts to find natural

and planted stands between 5 and 15

years old. These were used as data

points in the hazard maps. Each point

was located on a'map along with the percentage of loblolly or slash pines

infested at that point.

Plantation data were included only

for stands in which at least 30 'percent

of the trees were infected. All obser-,

vations from naturally regenerated

stands were entered.

2
The number of each stand was crossreferenced manually with another printout to determine the grid coordinates

for each stand. Using the coordinates

and the appropriate grid map, each data

point was located and drawn on another

base map.

The base map, including State outlines, was digitized on an Apple

Graphics Tablet by using a program

developed especially for this process.

Then all the data points were digitized

and stored. As the data points were

digitized, the percentage of infection

at each point was recorded on paper in

the same order as it was digitized.

Rust infection percentages were later

entered into a separate file with the

Applewriter IIe program.

.Three data sets showed State outlines, data point locations, and fusiform rust infection percentages. These

three data sets were uploaded to a mainframe computer program called "SYMAP" or

Synagraphic Mapping System. The program

is located at the Triangle Universities

Computer Center (TUCC) in Raleigh, NC.

The program was provided by the Laboratory for Computer Graphics and Spatial

Analysis, Graduate School of Design,

Harvard University.

The SYMAP program interpolated the

hazard values between all data points

based on their infection percentages,

distance from each other, and other

elective data given to the program. The

interpolation procedure was based on a

distance-weighted averaging technique

provided in the SYMAP program. Hazard

maps were then printed on an IBM printer

with overprint capabilities.

The original map contained many

small hazard zones, which implied

greater accuracy than was possible with

existing data. We therefore decided to

incorporate these smaller zones into

larger adjacent zones. This process was

done by hand.

The accuracy of interpolation by the

SYMAP program is greatly increased if it

is not halted by State borders. The

original map digitized for loblolly pine

was one that included the States of

Virginia, North Carolina, South

Carolina, and Georgia. However, the

borders between these States were

excluded so as to allow free interpolation by the SYMAP program across the

borders between all the data points.

The same process was used for slash pine

in Georgia and Florida.

The original maps (one for loblolly

and one for slash) were printed at a

scale of approximately 1:1,600,0OO.

They were then reduced to their present

size and redrawn on State maps with

county lines. Each State was drawn

separately from the original multi-State

'maps.

Independent sets of field data were

used to check the maps. The independent

data points were located on the hazard

map, and observed rust incidence was

compared with that predicted by the map.

Thirty independent, nonpermanent lob1011~ field plots were established in

central and southeastern Georgia. These

plots consisted of 100 trees from 5- to

15-year-old loblolly pine stands located

at random in the area. The same process

was also repeated for slash pine in

southern.Georgia and northern Florida.

In addition, knowledgeable individuals

were asked to review the maps based on

their field experience.

Results and Discussion

Figure 1 shows three rust-hazard

zones for slash pine in Georgia and

Florida. The high-hazard areas (more

than 30 percent of trees with infection

on or within 12 inches of the main stem)

in the natural range of slash pine are

in north-central Florida and in southeastern Georgia. Rust hazard is also

high for slash pine planted outside its

natural range.

The high-hazard areas are normally

bordered by areas of moderate hazard,

which, in turn, are bordered by areas of

low hazard. This pattern is consistent

with rust infection in the field, and

the computer mapping program was

designed to create zones moving from

high through moderate to low hazard. In

some cases, areas of high and low hazard

touch because space between the two

areas was too small to not be

biologically significant.

3
Percent Infection

o-s

IO-30

above 30

Figure l.--Fusiform-rust-hazard zones for slash pine

in Georgia and Florida. 1987. Percentages refer to

the average proportions of stems in stands 5 to 15

years old that are likely to have rust infections on

main stems or on live limbs within 12 inches of the

main stem.
Figure 2.--Fusiform-rust-hazard zc~nes for loblolly

pine in Virginia. South Carolina. North Carolina,

and Georgia. 1987. Percentages refer to the average

proportions of stems in stands 5 to 15 years old that

are likely to have rust infections on main stems or

on live limbs within 12 inches of the main stem.

” Percent Infection

o- 9

IO- 30

above 30
Figure 2 shows three rust-hazard

zones for loblolly pine in Virginia,

South Carolina, North Carolina, and

Georgia. The high-hazard zones are

concentrated in the Piedmont and Coastal

Plain of Georgia and South Carolina. In

Georgia they are more common from the

central part of the State to the coast;

in South Carolina they are somewhat

scattered.

The purpose of this study was to

develop maps which present a regional

view of fusiform rust occurrence. The

maps are intended to show where fusiform

rust is found and, in a general way,

where infection is most likely. Lines

on the maps, however, may suggest a precision and a predictability that do not

exist. For many reasons, actual percentages of pines infected in each zone

vary from high to low, with the percentage for,the zone being an average. Not

all stands in a high-hazard area have

more than 30 percent infection. In

fact, in some stands in high-hazard

areas, infection may be 0, and in some

stands in low-hazard areas, infection

may exceed 30 percent. Figure 2 does

show, however, that loblolly pines are

much less likely to be infected in

Virginia than in southeastern Georgia.

Once again, this does not mean that no

loblolly pine stand in Virginia has over

30 percent of its trees infected.

The maps are not intended to be an

on-the-ground management tool. They are

designed to assess rust incidence in a

general way and may be useful for largescale decisions, such as which part of a

State to deploy rust-resistant seedlings. Since the maps are based on FIA

data, they can be updated as new inventories are completed to show changes in

rust hazard over time. One of the

advantages of the computer-based map

procedure is that it ensures consistency

of interpolation of the subsequent data.

In the validation process, rust

incidence on 60 plots in three national

forests was used to check the hazard

shown on the map. Data from more than

100 field plots showing age, species,

percentage of rust, and location were

provided by Bob Schmidt, University of

Florida, and were similarly used. For

these data sets, a hazard map was constructed and the agreement between the

maps was compared. Thirty stands were

ground checked in central and southeastern Georgia to compare map hazard

with on-the-ground observations.

For the three national forests, the

maps agreed about 80 percent. That is,

the hazards of the two maps were the

same 80 percent of the time. For the

data set provided by Bob Schmidt, the

hazards agreed about 70 percent of the

time, but in all cases of disagreement,

the hazards were only one hazard class

apart. For the 15 stands checked in

southeastern Georgia, there was about 95

percent agreement, while the 15 stands

in central Georgia had only 70 percent

agreement. These data further support

that the maps are useful for general

information, but can lead to errors when

used in a site-specific manner.

Note: Mention of trade names is solely

to identify materials used and does not

imply endorsement by the U.S. Department

of Agriculture.
Literature Cited

Anderson, Robert L.; Cost, Noel D.; McClure, Joe P.;

Wistretta, Paul. 1981. Fusiform rust: acres of

slash and loblolly pine with 10, 20, 30, 40, and

over 50 percent of the trees infected with fusiform rust. Rep. 81-1-54. Asheville, NC: U.S.

Department of Agriculture, Forest Service, State &

Private Forestry, Southeastern Area. 8 pp.

Anderson, Robert L.; McClure, Joe P.; Cost, Noel D.;

Uhler, Robert J. 1986. Estimating fusiform rust

losses in five southeastern states. Southern

Journal of Applied Forestry 10:23'j'-240.

Campbell, W.A. 1965. Reducing losses from diseases

in pine plantations. In: A guide to loblolly and

slash pine plantation management in Southeastern

USA. Georgia Forest Research Council Report

14:146-155.

Dinus, Ronald J.; Schmidt, Robert A., eds. 1977.

Management of fusiform rust in southern pines:

Symposium proceedings; 1976 December 7-8;

*Gainesville, FL. Gainesville: University of

Florida. 163 pp.-

Jacobi, William R.; Anderson, Robert L.; Cost, Noel

D . 1981. Multiresource inventories: procedures

for assessing the damage caused by insects and

diseases. Res. Pap. SE-221. Asheville, NC: U.S.

Department of Agriculture, Forest Service,

Southeastern Forest Experiment Station. 11 pp.

.

Phelps, William R. 1973. Fusiform rust incidence

survey, 1971-73. Atlanta, GA: U.S. Department of

Agriculture, Forest Service, State & Private

Forestry, Southeastern Area. Unnumbered report.

31 PP.

Powers, H.R., Jr.; McClure J.P.; Knight, H.A.; Dutrow,

G.F. 1975 l Fusiform rust: Forest Survey incidence data and financial impact in the South.

Res, Pap. ~~-127. Asheville, NC: U.S. Department

of Agriculture, Forest Service, Southeastern

Forest Experiment Station. 16 pp.

Squillace, A.E. 1976. Geographic patterns of

fusiform rust infection in loblolly and slash pine

plantations. Res. Note SE-232. Asheville, NC:

U.S. Department of Agriculture, Forest Service,

Southeastern Forest Experiment Station. 4 pp.

United States Department of Agriculture, Forest

&s-vice. 1982. Field instructions for the

Southeast, 1982. Asheville, NC: U.S. Department

of Agriculture, Forest Service, Southeastern

Forest Experiment Station. 120 pp.