REPORT NO. 71-2-16 NOVEMBER 1970

3400

THE VARIABLE OAK LEAF CATERPILLAR IN

by

D.R. Kucera, Billy G. Gresham, and G. Barnum

ABSTRACT An cu>ea from north Little Rock to and including Greer's Ferry Lake was surveyed in September to determine the status and extent of defolia­ tion by the vcu>iable oak leaf caterpillar manteo (Dbldy.J. Results show 1.5 million acres of host type are defoliated from Pine Bluff to and including Piggott in the northeastern tip of the state. The red and white oak group are the preferred species. This is the first recorded outbreak of such a lcu>ge extent in Arkansas.

INTRODUCTION

Defoliation by the variable oak leaf caterpillar Heterocampa manteo (Dbldy.) was first reported this spring. The second de­ foliation, which is common for this species, was reported in early September, At this time the decision was made to survey the general area from which requests for assistance had been made. Billy G. GreshamY, G. BarnumY, and D.R. KuceraY conducted an aerial sketch map survey on September 21 and 22, 1970, Ground surveys had been conducted periodically since early September and continued through October. The purpose of this survey was to evaluate the status of the variable oak leaf caterpillar complex in central and north Arkansas,

1/ Arkansas Forestry Commission 2/ Division of Forest Pest Control.

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The aerial phase of this survey was accomplished using a sketch mapping technique in a Cessna 180, flight lines were flown parallel to ridges at an altitude of 1000 feet above the terrain. Ridges ran primarily east to west. flight lines were spaced at six mile intervals.

Defoliation was plotted on State forestry Commission county maps• (scale 1/2" = 1 mile). Numerous areas were ground checked before and after the flight to assist landowners requesting help. Land­ owner assistance was conducted by the Arkansas forestry Commission, and photographs taken by N. A. Overgaard of the Division of forest Pest Control.

Primary hardwood species being fed on were recorded while those with little or no detectable defoliation were not. All defoli­ ators found at each ground check were ranked empirically as to number and kind of larvae found.

RCSULTS

From the aerial survey and following ground checks, 1,5 million acres were found defoliated by a complex of,caterpillar larvae (Fig. 1). Gross acreage infested is over 2.5 million acres. Defoliation extends from Pine Bluff north to Greer's Ferry Lake and then east to Piggott. The largest single unit of defoliation is immediately north of Little Rock. All defoliation is either on state or private land.

The variable oak leaf caterpillar H. man.tea (Fig. 2) was the primary defoliator and the saddled prominent Heterocampa guttivitta (Walker) was the second most common. Commonly associated species in descending order of importance were an oak worm Anisota stigma (F.), yellow necked caterpillar Datana ministra (Drury), walking­ stick Diapheromera femorata (Say), walnut caterpillar Datana integerrima (G&R), a hag Phobetron pithecium (Smith), and numerous other defoliators.

Oaks were the most heavily defoliated, both the red and white oak groups. The following oaks are common in the area of infesta­ tion: white, blackjack, post, black, willow, water, and northern red. Other trees with visible defoliation included hickory, elm, and river birch.

DISCUSSION

This is the heaviest defoliation by the variable oak leaf cater­ pillar ever recorded in Arkansas although it has been previously

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Medium to heavy defoliation

Fig. 1. Variable oak leaf caterpillar defoliation in Arkansas, 1970. f . . ., ~·-: ... _,,,,, . ✓,r..··· ✓. "{ \~2,:,,.· / . . I -~··. .~ . ~-... ~ ' . . . • fl•' ·. : ...... \-. :-~-~ .... \..., ... ' . . 1

Fig. 2 Three phases of the variable oak leaf caterpillar. recorded in association with the walkingstick D, femorata. The largest single area of defoliation is immediately north of Little Rock and extends to Greer's Ferry Lake, Post and blackjack oak are the most !severely defoliated. Heaviest defoliation is found on the south 'facing slopes. In general, the susceptible host type is intermingled with farmland. Defoliation extends westward until stand composition changes to pine and eastward to predominantly farmland.

Because there are two periods of defoliation, the impact on sus­ ceptible trees is not well known but could become serious since o years of repeated defoliation causes branch dieback and also ee mortality. Spring defoliation probably causes more damage ~ nee it occurs when trees are actually growing while fall defoli­ ation occurs after growth has practically ceased.

Overall, infested trees are not of high commercial value. Larger, more vigorous trees in the valley are seldom defoliated. However, private landowners have been bothered by the nuisance of cater­ pillars falling onto people and also a buildup of frass on walkways, driveways, etc. Numerous requests for assistance have swamped the Arkansas Forestry Commission.

A control project over the whole area would be almost impossible because there are so many landowners with small lots and acreage. In addition, the scattered stands intermingled with farmland would be difficult to treat with an aerial spray program.

RECOMMENDATIONS

1, Should widespread defoliation be severe again in 1971 protection may become necessary. However, no control project should be ini­ tiated prior to another evaluation.

2. A biological evaluation should be conducted both in the spring and fall of 1971 to determine the trend of the variable oak cater­ pillar.

REFERENCES

Cambre, L.A., H. H. Galusha, and D. E. Ketcham. Evaluation of walkingstick defoliation on the Ouachita National Forest, Arkansas and . USDA For. Serv., SA, S&PF, Div. of For. Pest Control, Rpt. No. 62-132.

-3- Risley, J. H. The Saddled Prominent. State of Conser­ vation Department. pp. 29-30. 1970.

Grimble, D. G. and D. C. Allen. Identification of the larval instars of Heterocampa guttivitta (Walker) with notes on their feeding behavior. Jour. of Econ. Ent. 63:2, pp. 1201- 1203.

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