Some Possible Economic Conseqences of a Severe Outbreak of Tristeza to the Florida Orange Industry1

STOUT, SMITH, RIGGAN, CHEN-TUAN LI: TRISTEZA 21 SOME POSSIBLE ECONOMIC CONSEQENCES OF A SEVERE OUTBREAK OF TRISTEZA TO THE FLORIDA ORANGE INDUSTRY1 Roy G. Stout, Cecil N. Smith, Wilson B. sources of a severe strain of the tristeza virus; (2) wide spread distribution of Toxoptera citri RlGGAN AND CHEN-TUAN Li cidus (Kirk.) ; (3) the combination of items 1 and University of Florida 2, resulting in very rapid spread of the tristeza virus and subsequent decline of trees within a Gainesville three to five year period; and (4) all trees on The Florida citrus industry, like most agri sour orange rootstocks being out of production within the period specified. cultural enterprises, is plagued from time to time Trees on sour orange rootstocks accounted with natural disorders that temporarily . reduce for 31.1 percent of all orange trees in Florida output. The most recent such disasters have been at the completion of the 1954-57 citrus tree cen freezes and hurricanes. This year the Mediter sus (5). Assuming no differences in yields due ranean fruit fly has presented a threat to the to rootstocks, this would mean a 31.1 percent loss industry. in orange production from a severe outbreak of Another potential threat to the citrus in tristeza (Table 1). The distribution of trees on dustry is tristeza. It has been estimated that sour orange rootstocks varies somewhat by age this virus caused the death of some 20 million groups, with a low of 20.5 percent in the less citrus trees in South America during the period than 5 year old new plantings (excluding non- from 1927 through 1957 (4). When a severe out bearing resets) to 44.6 percent in the 15-24 year break occurs, affected trees succumb rapidly. The old group. The proportion of the total on sour incidence of tristeza in Florida during the past orange rootstocks increased during the planting ten years has not been as severe as many anti period 1932-42, but a gradual decline occurred cipated because of three factors: (1) the absence after that. of the aphid Toxoptera citricidus (Kirk.), which has been responsible for the rapid spread of An analysis of the movement of nursery stock tristeza in other parts of the world; (2) the fact since the completion of the census shows that that in general, the strains of tristeza found in 28.6 percent of the new orange tree plantings Florida have been mild ones; and (3) the bud- from 1957 to 1961 were on sour orange rootstocks wood certification program, which has reduced (7). Although less than a fourth of all plantings the spread of tristeza through infected buds (6). in 1957-58 and 1958-59 were on sour orange root- However, if a virulent strain of this virus were stock, nearly a third of the trees planted in 1959- to become prevalent in Florida and the aphid 60 and 1960-61 were on this stock. Evidently Toxoptera citricidus (Kirk.) responsible for its those planting sour orange rootstocks have con rapid spread were to be prevalent, a large por sidered that the risks involved in a possible loss tion of citrus trees on rootstock not tolerant of due to tristeza do not offset the desirable charac tristeza virus would most probably be damaged. teristics possessed by this rootstock. Trees on The purpose of this paper is to estimate the sour orange rootstocks are considered to bear possible losses in orange production if a severe fruit with high solids content and with other outbreak of tristeza were to occur. No considera good qualities. Furthermore, it is well recognized tion has been given to its effect on grapefruit. that sour orange is one of the most cold resistant The basic data utilized in this analysis are from rootstocks. This is evidenced by the high propor the Florida citrus tree census of 1954-57. tion of sour orange rootstocks in the colder This analysis of economic effects of a postu Northern Fringe areas. Likewise, it apparently lated tristeza epidemic is based on the following is well adapted to the conditions in the East Coast assumptions: (1) the abundant presence of area, since a high proportion of orange trees there are on sour orange rootstocks. The possible losses that would occur by geo iThis paper was adapted from a portion of the doctoral graphic areas within the state can be inferred dissertation by Chen-Tuan Li, Input Interactions in Florida Orange Production, University of Florida, August 1962. from the data in Table 1 and Figure 1. The Florida Agricultural Experiment Stations Journal Series largest losses, percentage wise, would occur in No. 1568. 22 FLORIDA STATE HORTICULTURAL SOCIETY, 1962 TABLE 1.—Proportion of all Florida orange trees budded on sour orange rootstock, by age groups and areas, 1957. North West Upper Lower East Age Group Total Fringe Coast Interior Interior Coast Percent Non-bearing reset 86.1 27.2 32.1 7.9 84.3 33.5 0-4 years 47.4 24.4 13.8 9.0 63.7 20.5 5-9 years 71.4 25.3 22.7 8.6 79.6 27.7 10-14 years 73.2 37.6 34.0 10.5 90.6 35.2 15-24 years 91.1 31.0 44.5 9.8 92.1 44.6 25 years and over 88.4 16.5 33.0 3.6 87.3 31.1 All ages , 73.8 24.4 27.7 6.9 86.3 31.1 the East Coast and Northern Fringe areas. site change in price of about 1.6 percent. But Roughly 83 percent of the East Coast and 76 a study of supermarket sales of fresh oranges percent of the Northern Fringe production would by Godwin (3) indicated an elastic demand. be lost if tristeza wiped out all orange trees on Therefore, it is conceivable that loss of 30 per sour orange rootstocks. The smallest area per cent of the orange crop could result in an increase centage loss would occur in the Lower Interior— in total dollar sales by growers. However, the about 7 percent. structure of production and handling costs would The proportion of trees on sour orange root- be greatly affected by a sudden drop in the volume stock by varieties indicates that a tristeza out handled. Although growers as a whole would break would destroy about 47 percent of all navel probably receive higher incomes, even this would orange production (Table 2). Early seedy varie not comfort those individual grove owners who ties would lose about 35 percent of their produc sustained total losses. tion, and Valencias 19 per cent. Jaffa orange Let us now examine some of the losses to production would remain fairly stable, since only growers, labor employed in producing, picking 12 percent of Jaffas are on sour orange root- and processing oranges, vendors of packing and stocks. processing materials and other agencies involved in supplying inputs used by citrus growers, hand TABLE 2.—Proportion of major varieties of orange trees on sour orange rootstocks, 1957. lers and processors. For purposes of this analy sis, let us assume an orange crop of 125 million Variety Percent sour orange boxes—a crop of the size likely to be produced Hamlin 27.6 several years hence. It is further assumed that Early Seedy 35.5 Navel 47.1 21 million boxes would be sold fresh to the do Jaffa 12.1 Mid-season Seedy 26.3 mestic and export market and that 104 million 19.2 Valencia boxes would be processed. If 30 percent of all orange trees were killed by The price elasticity of demand must be con a tristeza epidemic, the crop would be reduced by sidered before one can evaluate whether total 37.5 million boxes. It is postulated that 6.3 returns from the orange crop would be decreased million boxes of this quantity would have been in response to a reduction in supply. The exact sold fresh and 31.2 million boxes would have been nature of the present demand has not been de processed. termined. Studies in the past, based on the fresh fruit market before the large growth in concen The income loss to orange growers from a trate sales, indicated that the demand for oranges, 30 percent decline in orange production is diffi like that for most other agricultural commodities, cult to estimate. As noted above, an assessment was inelastic. A study by Fox (2) showed that a of such a loss would require more up-to-date in 1 percent change in supply would cause an oppo formation on the price elasticities for oranges STOUT, SMITH, RIGGAN, CHEN-TUAN LI: TRISTEZA 23 1,000 Percent Percent on Area Trees of Total Sour Orange Rootstock North Fringe 2,981 9.5 73.8 Upper Interior 10,937 34.9 27.7 Lower Interior 9,648 30.8 6.9 West Coast 5,139 16.4 24.4 East Coast 2,647 8.4 86.3 All Areas 31,352 100.0 31.1 Figure 1.-Number of orange trees, percent of total and percent on sour orange rootstocks, 1957 and competing products than is now available. would be $45,875,000. With costs of growing of The on-tree prices per box used here are not $25,875,000, the net loss to these growers would based on statistically derived demand relation be $20 million. But even this is not a realistic ships and are utilized only for purposes of illus figure. As brought out previously, it is probable tration. If, with a 125 million box crop, the that the on-tree value of a 87.5 million box crop average on-tree price were $1.60, the total loss would be higher than that of a 125 million box from the failure to market 37.5 million boxes of supply.

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