524 



Yearbook^ of Agriculture 1949 



Experience dictates that a burn for 

 this purpose include at least 200 acres; 

 results would be better on even larger 

 units. The occurrence and virulence of 

 brown spot disease is so variable that 

 no time formula for treatment can be 

 followed. In some areas the disease 

 was not sufficiently prevalent to justify 

 burning, while in others a dangerous 

 degree of infection did not appear un- 

 til the fifth year. Of considerable sig- 

 nificance are indications that one fire 

 treatment often is enough to bring the 

 seedlings through into height growth. 



Our best guide is: Never burn un- 

 less necessary; necessity must be deter- 

 mined by an annual reconnaissance 

 that computes the extent of infection 

 present and maps for treatment any 

 areas where infection is severe. 



Experience indicates that when (be- 

 cause of tardy treatment) only about 

 one-quarter of the stock recovers its 

 health, there is a net gain from reburn- 

 ing 2 years after the first fire. The in- 

 fection must therefore be detected and 

 burned promptly, before the disease 

 has had time to sap the vigor of the 

 plants. 



The results from fire treatment have 

 generally been successful. Plantations 

 and areas of natural reproduction 

 which were treated in time are now 

 healthy, well-stocked stands of sap- 

 lings. Even in plantations where fire 

 was excluded so long that some mor- 

 tality had set in and the remainder 

 looked hopeless, the recovery resulted 

 in healthy if understocked stands. 



RELEASE BURNING is another aspect. 

 For reasons not yet clearly measured, 

 longleaf seedlings not seriously diseased 

 sometimes will remain in the grass 

 stage and fail to start height growth 

 for as long as 12 years. The reason 

 probably is a combination of deficien- 

 cies in food, moisture, and sunlight, be- 

 cause of the competition of dense 

 stands of grasses and shrubs. Frequently 

 it was noted that height growth began 

 after a wildfire had burned such areas. 



To determine whether some of these 

 lost years of growth could be saved, a 



program was started for burning vary- 

 ing age classes of the delayed-growth 

 stands. The study, not yet completed, 

 indicates tentatively that height growth 

 will begin the second spring following 

 a prescribed burn that removes the 

 grass mat and kills back the bushes, 

 worthless brush, and hardwood species. 



Fire has been used successfully to 

 kill back encroachments of titi, gall- 

 berry, and myrtle and permit the estab- 

 lishment of pine seedlings. A large area 

 in Florida burned for this purpose now 

 supports a good stand of slash pine 

 seedlings. 



Scrub oak thickets have been burned 

 in all seasons and with varied intensi- 

 ties of flame. Usually fuel under the 

 thickets is light and patchy; in them, 

 high-intensity fires are impossible. 

 Summer fires have given favorable re- 

 sults on small areas here and there 

 within a large burn. We are unable yet 

 to point to conclusive examples of suc- 

 cessfully reducing by fire treatment the 

 scrub oak canopy generally over com- 

 mercial-size areas. 



The valuable loblolly pine assumes 

 the role of an undesirable species 

 when it encroaches on a true longleaf 

 pine site that has a stand of grass-stage 

 seedlings. If it is not controlled, the 

 loblolly takes early ascendancy and 

 usually smothers out the longleaf. The 

 loblolly lacks the long taproot with 

 which nature equips the tree she de- 

 signed for this site and cannot reach 

 down through the dry topsoils to the 

 water table. It soon loses its vigor, be- 

 comes easy prey to deforming or killing 

 Cronartium infection, and produces an 

 inferior stand. 



Burning in loblolly sapling stands to 

 remove fuel in strips has been under 

 controlled tests for only one season. 

 Preliminary findings are that the areas 

 treated show low damage; perhaps 

 burning techniques can be evolved that 

 will make it practical, at low cost and 

 low damage, to break large areas of 

 fire-vulnerable stands into small blocks 

 within which an intensive fire can be 

 confined. 



Loblolly areas in parts of southeast- 



