REPORT NO. 66-3-13 JULY 1966 BIOLOGICAL EVALUATION or SOUTHERN PINE BEETLE INFESTATIONS ON THE NATIONAL FORESTS IN TEXAS

by

N. A. Overgaard and Henry H. Galusha, Jr.

INTRODUCTION

A biological evaluation of southern pine beetle infestations on the National Forests in Texas (fig. l) was made on June 27 through July l, 1966 by N. A. Overgaard. He was assisted in the evaluation by D.R. Kucera, P. J • Barry, C • D. Turner, A. D. Guillory, and W. 1-1. Yeager of the Division of Forest Insect and Disease Control. Aerial surveys of the Forests were made on June 20-22, 1966, and the evaluation was made on the basis of ground checks of these surveys. Southern pine beetle was reported on the Sam Houston, the Angelina, and the Davy Crockett National Forests in 1962, but was not found on the Sabine National Forest. Since then, southern pine beetle activity has continued on the Big Thicket District of the Sam Houston National Forest and on the Angelina National Forest, but has not been found on any of the other forests until the recent survey.

The beetle was found for the first time on the Yellowpine District of the Sabine National Forest, and again on the Big Thicket District, and the Angelina National Forest during the current survey.

Southern pine beetle populations are apparently declining on all in­ fested areas of the National Forests in Texas. Recent hot, dry weather conditions and competition from~ beetles may be responsible for the decline.

TECHNICAL INFORMATION Causal agent.--Southern pine beetle, Dendroctonus frontalis Zimm.

Host trees attacked.--Loblolly pine, Pinus taeda L., and shortleaf pine, Pinus echinata Mill.

Tvpe of damage.--Damage caused by the southern pine beetle is tree mortality resulting from adult feeding and the construction of egg galleries in the cambial region of the host. Blue stain fungi, Ceratocystis spp., are introduced by the causal agent, speeding the rate of kill and reducing the salvage value of the host. 0 IO U - "'-4 o /, N,At.:t ..

-la- Biological data.--Southern pine beetle brood development was poor in all of the infested trees examined • .!£!_beetles were competing with southern pine beetle for food supply and appeared in many cases to be the primary attacker, Ostamid and clerid predators were present, but not in unusual numbers.

Environmental factors.--Weather was generally hot and dry during June. Hot, dry weather can cause rapid drying of the bark after attack which results in poor brood development. Dry weather also favors build-up of _!E,! beetle populations. Location and intensity of outbreak.--Six hundred and thirty-four single-tree spots and 234 multiple-tree spots were observed during the aerial sketch-map survey of the National Forests in Texas. Flight lines were spaced at 2-mile intervals providing 50 percent coverage of the Forest. Seventy-five single-tree and 51 multiple-tree spots were examined on the ground for southern pine beetle. A total of nine multiple-tree spots and one single-tree spot were found infested with the beetle within the National Forest boundaries. Four infested spots were found on the Big Thicket District, four on the Angelina N. F., and two on the Sabine N. F. Three small active spots were found on private land west of the Sabine N. F. Results are summarized in Table l.

No large spots of southern pine beetle were found on the Big Thicket District. The largest multiple spot contained 21 trees; however, only two of these were still active. Intensive control work was underway and some of the spots observed from the air had already been treated by the time they were ground checked. The most of the southern pine beetle activity on this District was found between Shepherd and Cleveland. Two southern pine beetle infested spots were found in the northern por­ tion of the District for the first time since 1962.

Southern pine beetle was again present on the Angelina National Forest near Broaddus, Texas. Populations were light with few active trees present in the spots checked. However, two very active spots of 200, and 70 trees respectively, were recently found by District personnel, Control crews were workine at the time of the evaluation,

The beetle was found for the first time on the Yellowpine District of the Sabine National Forest in Sabine County, southeast of Pineland, Texas. Only two spots were found with a total of three active trees present. Southern pine beetle activity was very light, with the beetle being secondary to .!J2!. and black turpentine beetles. Three additional small active spots were found on private land west of Bronson, Texas. No southern pine beetle was found on the Davy Crockett National Forest, or the Raven District of the Sam Houston National Forest.

-2- Table 1, Summary of Results of Aerial Survey for Southern Pine Beetle on the National Forests in Texas Spots Observed Spots 1 Spots infested Spots with Percent spots from air • ~ound checked I with SPB SPB emer,!led 'ground checked Area ' Single 'Hultiple, 'Single 'Multiple 'Single 'Multiple 'Single 'Multiple ' infested w/SPB Sam Houston N. r.

Big Thicket R. D. 1211 59 9 111 0 ii 8 11 17

Raven R. D. 81 20 19 3 0 0 0 0 0

Aneelina N. r. 1111 80 17 111 l 3 2 ii 13

Davy Crockett N. F. 117 31 12 ii 0 0 0 0 0 I "'I Sabine N. r. 165 1111 18 16 0 2 2 0 6

Total 6311 2311 75 51 l 9 12 15 DISCUSSION Southern pine beetle populations appeared on the decline at the present time on the National Forests in Texas. Brood development was poor and ~ beetles were actively competing for food supply with southern pine beetle in many of the trees examined. The southern pine beetle normally declines in activity later in the summer. Apparently, however, the decline in these areas has started earlier than usual this year. Although southern pine beetle popula­ tions are generally on the decrease on the National Forests in Texas, activity is continuing and populations could increase again later in the year when conditions become more favorable for the beetle. IMPACT OF CONTROL ON OTHER RESOURCES The spraying of a 0.5-percent of gamma isomer benzene hexachloride directly on the surface of the infested portions of the trees will not have any adverse effects on other resources. RECOMMENDATIONS 1, A 100-percent sketch-map survey should be made on the Yellowpine District by the Division of Forest Insect and Disease Control to further evaluate the location and intensity of the infestation.

2. District personnel should assist in the survey for the purpose of training. 3. The Big Thicket and Angelina Districts should continue controlling active spots of southern pine beetle according to the District con­ trol plan whenever found.

4. All Districts should continue to notify Texas Forest Service per­ sonnel of active southern pine beetle spots on private land within National Forest boundaries.

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