Article Figures & Data
Figures
- Fig. 1.
A diseased elm being girdled to disrupt root-graft transmission of the fungus to adjacent elms.
- Fig. 2.
Girdling process: (a) initial parallel cuts made with a chain saw to girdle a diseased elm, (b) sapwood removed from between the initial saw cuts, and (c) a third cut made into the wood to assure vessels are severed.
- Fig. 3.
Number of elms surviving three sanitation practices judged against control-program performance levels.
- Fig. 4.
Percentage increase in elms saved by prompt or girdling-plus-prompt removal compared to the delayed removal program.
Tables
- Table 1.
Comparison of three diseased-elm-removal practices based on a 5-year study by 1,000-tree units.
Treatment and year Elmsa Survey Historical costs (dollars)b Beginning of season Diseased removed Girdling Removal Total Girdling-plus-prompt removalc 1974 1,000 56 498 138 11,254 11,890 1975 944 35 517 95 7,683 8,295 1976 909 47 518 132 10,796 11,446 1977 862 39 518 115 9,399 10,032 1978 823 69 519 217 17,802 18,538 Total 246 2,570 697 56,934 60,201 Prompt removalc 1974 1,000 47 500 9,446 9,946 1975 953 39 522 8,562 9,084 1976 914 65 518 14,930 15,448 1977 849 58 505 13,978 14,483 1978 791 61 500 15,738 16,238 Total 270 2,545 62,654 65,199 Delayed removald 1974 1,000 63 267 10,560 10,827 1975 937 60 273 10,985 11,258 1976 877 112 268 21,456 21,724 1977 765 79 245 15,879 16,124 1978 686 95 233 20,425 20,658 Total 409 1,286 79,305 80,591 ↵aElm loss data from Barger 1977, Barger, Cannon, and DeMaggio 1982.
↵bAdjusted from 1972 cost data (Cannon and Worley 1976) with the average wholesale price index each year for 1974 through 1978 with the method of Cannon and Worley (1980).
↵cSurveys made in mid-June, when 61 % of the total diseased elms were identified; mid-July, 32%; late August, 7%. Survey cost and girdling cost (in 1978 dollars) set at $51 per hour. First survey at 34 cents per tree, subsequent two surveys at 1 % disease rate at 15.5 cents per tree each survey. Cost of intensive tree removal set at $258 (cost of conventional removal plus 20% for extra effort required).
↵dCosts (in 1978 dollars) based on data from Cannon and Worley (1976): one survey at 34 cents per tree, and conventional removal during dormant season at $215 per tree.
- Table 2.
Savings in cost of control based on a 5-year study of 3 tree removal strategies, by 1,000-tree units.
Year Girdling-plus-prompt versus Prompt versus Delayed Prompt Delayed $ % $ % $ % 1974 (1.944)a (16) (1,063) (9) 881 8 1975 789 9 2,963 26 2,174 19 1976 4,002 26 10,278 47 6,276 29 1977 4,451 31 6,092 38 1,641 10 1978 (2,300) (14) 2,120 10 4,420 21 Total 4,998 8 20,390 25 15,392 19 ↵aBracketed numbers represent “negative savings” or losses.
- Table 3.
Statistics of girdling time for categories of elms observed to have Dutch elm disease.
Category No. Percent of total Girdling time (min) Mean Standard deviation Convoluted 20 33 5.0** 2.059 Nonconvoluted 10-20 in. dbh 17 28 2.5** 0.881 21-38 in. dbh 24 39 3.5** 1.215 All elms 61 100 3.7 1.749 ↵a**Means significantly different from each other at the 0.01 level, student’s t test.
More elms at less cost
Control tactic Elms remaining after 5 years Ave. total cost for 5 years No. per thousand % increase Dollars per tree % decrease Delayed removal 591 81 Prompt removal 730 20 65 20 Girdling-plus-prompt removal 754 28 60 25
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