No. 114 

1961 

THE VIRGINIA PINE SAWFLY IN 1960 

--A SPECIAL COOPERATIVE REPORT 

An outbreak of the pine sawfly, Neodiprion pratti 

pratti (Dyar), has existed in Maryland since 1955. By 1959 

the insect had spread throughout 14 million acres in the 

Coastal Plain and Piedmont of Virginia and into several 

North Carolina counties. Because egg surveys conducted in 

the spring of 1960 indicated a continuation of the epidemic, 

an aerial survey was conducted to further evaluate the situation. This report contains a summary of this latter investigation. 

The aerial survey was conducted with funds and personnel contributed by the following organizations: Beltsville Forest Insect Laboratory, U. S. Forest Service; Maryland Department of Forests and Parks; North Carolina Forest 

Service; Northeastern Forest Experiment Station, U.S. Forest 

Service; Southeastern Forest Experiment Station, U.S. Forest 

Service; and Virginia Division of Forestry. 

Procedure 

The method used was an aerial strip survey along predetermined flight lines. County highway maps at a scale of 

1 inch = 2 miles were used for base maps. Observers recorded conditions along 5-chain strips on both sides of the airplane, using the operation recorder system, which has proved 

successful for many years on similar surveys. Flight lines 

were spaced at 10-mile intervals, although the maps were 
1 PERCENTAGE OF PINE TYPE IN AREA ALONG FLIGHT LINE 

LIGHT DEFOLIATION (5% or less of foliage removed) 

MODERATE DEFOLIATION (6-95% of foliage removed) 

HEAVY DEFOLIATION (96-10% of foliage removed) 

_ -0----- 

- Miles 

0 10 20 30 
prepared to permit observations at 5-mile intervals where 

conditions varied or where additional data were required. 

Fairly uniform damage was encountered over extensive 

areas; and, in several instances wheye defoliation was 

light, flight-line distances were increased to 20 miles. The 

locations of flight lines are shown in figure 1. 

Three classes of defoliation were distinguished by 

the observers : 

Light - 5 percent or less foliage removed. 

Moderate - 6 to 95 percent foliage removed. 

Heavy - 96 to 100 percent foliage removed. 

Along the flight lines, pine stands showing no visible insect feeding were also recorded, 

The survey was begun on May 20 in North Carolina and 

was completed on May 27 in northern Maryland. In total, 

15.6 hours of flying time were required. 

In mapping the area, the following timber type designations were used: 

Pine - 50% or more of the stand in pine 

Pine-hardwood - 25 to 50% of the stand in pine. 

Hardwood - less than 25% of the stand in pine. 

On the map, pine type is shown as a percentage of the 

land area observed in each 10-mile segment along the flight 

lines. For example, on the flight line above Roanoke Rapids, 

N. C. (bottom of map, in center), the number 48 indicates 

that 48 percent of the land area in that 10-mile segment had 

a forest cover of pine type. 

Since the sawfly attacks pines just as severely in 

predominantly hardwood stands as it does in pine stands, the 

pine and pine-hardwood areas were combined in recording defoliation. 

Figure 1.--Pattern of defoliation by Virginia pine 

sawfly in Maryland, Virginia, and North Carolina. 

The map is based on an aerial survey made in 1960. 

t 
No effort was made to separate pine species in the 

type-mapping, even though it is recognized that loblolly 

pine is not a preferred host when Virginia pine, pitch pine, 

and shortleaf pine are available. Loblolly pine is a major 

component only in the forested areas along coastal Virginia 

and in southern Maryland, 

Discussion 

Figure 1 shows the distribution and intensity of defoliation by N. pratti pratti during 1960 within the three 

states included in this survey. The development of the outbreak for the years 1955-60 is presented in figure 2. An 

acreage summary for this period is shown in table 1. 

Although the total acreage infested in 1960 has decreased by approximately 4 million acres from that recorded 

in 1959, the decrease is limited almost entirely to the 

periphery of the epidemic area, where only light feeding had 

been noted previously. Much of this reduction in infested 

acreage was in southeas tern Virginia, where loblolly pine is 

the predominant species and the preferred Virginia pine occurs only as scattered trees. Egg surveys had shown that the 

sawfly was present in the peninsulas between the Potomac, 

Rappahannock, and York Rivers; but the flight lines were 

terminated as shown in these coastal areas because of the 

sparseness of Virginia pine. 

This was the first year that an aerial survey was 

conducted over the entire outbreak area, and thus the limits 

of these forest types were better defined. Throughout the 

interior of the defoliated area, feeding injury has intensified and zones of heavy defoliation have doubled. For 

example, the areas of heavy defoliation have increased from 

14 million acres in 1959 to 3 million acres in 1960. 

The aerial survey not only gives an accurate overall 

picture of damage to the susceptible pines, but also directs 

the entomologist to the areas where he can intensify his egg 

Figure 2.--The trend of defoliation damage by the Virginia pine sawfly in Maryland, Virginia, and North 

Carolina, 1955-60. 
LIGHT MODERATE HEAVY 
Table 1 .--Virginia pine sawfly defoliation, 1955-60 

(In thousands of acres) 

Light Moderate Heavy 

Year - Total 

North North North Maryland Virginia Maryland Virginia Maryland Virginia Carolina Carolina Carolina 

GROSS ACREAGE 1 

1955 156 -- -- 170 - - - - - - - - - - 326 

1956 258 40 - - 86 - - -- -- - - - - 384 

1957 92 1 1,372 - - 929 69 - - - - - - - - 3,291 

1958 - - - - - - 2,625 4,473 652 100 - - - - 7,850 

1959 642 5,835 -- 817 5,141 36 5 142 1,341 48 14,331 

1960 252 1,404 331 975 3,487 298 262 2,750 5 8 9,817 

NET ACREAGE^ 

1955 15 - - - - 14 - - - - - - - - - - 2 9 

1956 19 4 - - 9 - - - - - - - - - - 32 

1957 129 262 - - 130 13 - - - - - - - - 534 

1958 -- - - - - 315 1,131 13 12 - - - - 1,471 

1959 77 1,476 - - 9 8 1,301 31 17 339 11 3,350 

1960 32 355 84 360 882 75 72 696 15 2,571 

'~ncludes all forest types and land areas where defoliation was recorded. 

2~ased on percentage of pine type and pine-hardwood type, from aerial survey or Forest Service inventory records. 
surveys and biological appraisals. Thus he can bolster his 

prediction of what the sawfly can be expected to do in 1961 

and what areas need particular attention. One additional 

benefit arises when figure 2 is reviewed; here the accrued 

defoliation of past years can be determined at a glance and 

a more intelligent decision can be made as to the effect 

that continued heavy defoliation may have on stand vigor and 

growth loss. 

1 

--T. McINTYRE 

R. C. HELLER 

C. L. MORRIS 

l~r. McIntyre is Entomologist, Laurel Research Center, 

Northeastern Forest Experiment Station, Forest Service, U.S. 

Department of Agriculture, Laurel, Md. 

Mr. Heller is Research Forester, Beltsville Forest 

Insect Laboratory, Forest Service, U. S. Department of Agriculture, Beltsville, Md. 

Mr. Morris is Chief, Forest Insect and Disease Investigations, Virginia Division of Forestry, Charlottesville, 

Va.