64-1-12

5230 MAY 1964

EVALUATION OF CONE LOSSES ON THE BRICK CHURCH SEED PRODUCTION AREA FRANCIS MARION NATIONAL FOREST,

By

W, M. Ciesla and R. T. Franklin

INTRODUCTION

An evaluation of coneworm infestations on the Brick Church longleaf pine seed production area, located on the Witherbee District of the Francis Marion National Forest, was made March 18, 1964, Specimens of damaged firstyear cones were received from this 55 acre area during February 1964 and larvae collected from the damaged cones were subsequently identified as Dioryctria clarioralis (Wlk,) (: Phycitidae) J/, The objective of this evaluation was to arrive at an estimate of the loss to the 1964 cone crop on this area after the first growing season.

This survey was made in conjunction with the removal of undesirable trees from the seed production area. Fifteen trees, scheduled for removal, were randomly selected for the survey and cut. All first year cones were collected from the sample trees, Sound cones were separated from damaged cones in the laboratory and were dissected to determine the causal agent(s) responsi­ ble for the injury.

Results indicate that at least 44, 8 per cent of the cones were destroyed during the 1963 growing season. Most of the loss was due to infestation by the coneworms. Dioryctria spp,

TECHNICAL DATA

CAUSAL AGENT. --The primary causal agents responsible for the damage were coneworms of the genus Dioryctria, D. clarioralis was collected from the infested material, and it is probable that other species in this genus are also involved,

J/ Det. E. P. Merkel, Southeast Forest Expt, Sta,, Olustee, . HOST TREE ATTACKED.--Longleaf pine, ~ Jls!lustr1s Mill.

TYPE OF DAMAGE.--Larvae of the genus Dioryctria occur regularly onlongleaf pine. The larvae tuMel extensively in the host material, extruding frass and resin to the surface. j2. clarioralis larvae construct a characteristic blister of resin coated silk over the entrance holes, ejected frassaccumulates inside these blisters (Ebel. 1964). Attack in first year cones results in death of the developing cone and a consequent 100 per cent seed loss, whereas attacks in second year cones may result in only a partial seed loss. Damage to first year cones and vegetative buds was observed on the Brick Church area.

BIOLOGICAL DATA. --Associated taken from the material collected included Lepidopterous pupae, which were reared to the adult stage and identified as ostrinella (Clemens) (Phycitidae) y', and a single Coleopterous pupae, which was successfully reared to the adult stage and identified as Ernobius spp, (Anobiidae) y. These insects are secondary feeders which attack dead and dried out cones.

A number of Dipterous adults and a single Ichneumonid wasp were also collected from the damaged material. These have been submitted for species identification.

LOCATION AND EXTENT OF INFESTATIONS. --Cone collections made on the Brick Church seed production area indicate that an estimated 44. 8+ 4.2 per cent V of the first year cones had been destroyed. Approximately two­ thirds of the dead cones had feeding damage typical of that caused by Dioryctria spp, The remainder had no visible damage; the reason for their death was undetermined.

Cone production was extremely variable on the trees sampled; ranging from 0 to 195 cones per tree (Table l). Cone loss on individual trees was also extremely variable and ranged from a low of 5. 2 per cent to a high of 100 per cent. A scatter diagram of per cent destroyed over total cones produced indicates no apparent correlation between cone production and subsequent loss (Figure 1),

Table 1. --Cone Production and Loss After One Year, Brick Church Seed Production Area, Francis Marion National Forest, March 1964.

First Year Cones Mean Standard Deviation Range Production per tree 35.27 + 47, 42 0 -195

Loss per tree 15,80 + 17.66 0 - 59

1,/, V Det, E. P. Merkel, Southeast Forest Expt, Sta,, Olustee, Fla. JI 95 per cent confidence limits.

-2- 100 • • • • 90

60 70 • • 60 ,' • ~ D ~ 50 "D • "~ 40 " ~ 30 • ~ • 0 .) 20 • • 10 • 0 50 100 150 200 Cones Produced Fig. l - Scatter diagram of cone lose over cone production, Brick Church Seed Production Area, Francis Marion National Fores1,, March 1964. DISCUSSION

The estimate of loss to the first year cone crop on the Brick Church area may be considered, perhaps more realistically, an estimate of losses which occurred during the period six months prior to the time this survey was made, In this case, damage observed in March 1964 probably occurred between September-October 1963, and March 1964. Any damage which may have occurred prior to this time was probably missed due to abortion and deterioration of damaged cones.

Surveys to determine the extent of cone crop losses have, to date, been limited. Therefore, it is difficult to ascertain as to whether the loss by Dioryctria on the Brick Church area is abnormally high, resulting from an epidemic population or normal and resulting from an endemic population. Data are available for a similar survey made in slash pine in Florida (Merkel 1961) which indicate that a 28.6 per cent loss occurred to the 1960 cone crop near Olustee, Florida after two growing seasons; 19.5 per cent ofwhich occurred during the first year. The losses due to Dioryctria on the Brick Church area are relatively high when compared to these data, particularly when it must be considered that the 1964 cone crop is subject to another season of infestation by Dioryctria as well as attack by the seedworms Laspyresia spp. resulting in additional seed loss.

Seed and cone insects have only recently become important due to the establishment of seed production areas and seed orchards designed to produce high quality seed for reforestation. Therefore, it is difficult to assess their importance on the basis of one survey or to decide for or against control on the basis of one survey. Before chemical control for Dioryctria, or any seed or cone damaging , can be considered,a resource evaluation must be made to determine if the area produces enough seed to satisfy the current demand.

Additional information regarding Dioryctria is required to determine when chemical controls are needed. Apparently, the damage caused by Oioryctria and other insects affecting longleaf pine flowers, cones, and seeds is subject to considerable year-to-year fluctuation. The factors influencing theabun.; dance of these destructive insects are not yet fully understood and at present there are no means available by which high seed losses may be predicted in advance. This information may be obtained from continued research in this field as well as continued evaluations designed to assess the trends of these insects.

-4- RECOMMENDATIONS

1. Surveys to determine the loss to the 1964 cone crop on the Brick Church Seed Production area during the second growing season should be made during late October so that an estimate of overall cone loss may be obtained.

2. A survey should be made during March 1965 to determine the loss due to Dioryctria during the first growing season of the 1965 cone crop.

REFERENCES

Ebel, Bernard H. 1963. Insects affecting seed production of longleaf and slash pines, their identification and biological annotation. USDA, Forest Service, Southeastern Forest Expt. Sta., Asheville, N. C. Research Paper SE-6.

Merkel, E. P. 1961. A study of losses in the 1960 slash pine cone crop. USDA, Forest Service, Southeastern Forest Expt. Sta., Asheville, N. C. Research Note 164.

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