By Ariel Singerman
Citrus growers in Florida are now allowed to inject their trees with oxytetracycline (OTC) to try to control Candidatus Liberibacter asiaticus and/or suppress citrus greening. The use of OTC is expected to improve the trees’ health and, in turn, increase yield. In this article, cost estimates are used to address the question of what yield response is needed to make the treatment economically viable.
Oxytetracycline can be applied only once a year to bearing trees and cannot be applied for more than two consecutive years. Table 1 provides estimates of the annual materials, injection, labor and total cost of injecting trees with OTC on a per-tree and per-acre basis for different trunk sizes when using a compound concentration of 5,500 parts per million (ppm). Such concentration is the one suggested for bearing trees in poor health condition.
The cost of the compound is $106 per pound based on the average of quotes obtained for the least expensive of the two oxytetracycline products available. The cost of the injector and the cost of labor are based on the information provided on the website of one of the compound manufacturers. The manufacturer estimates that the cost of an injector is $18, and it can be used between 100 and 200 times, so this study uses the average (150).
Assuming a tree density of 150 trees per acre, the corresponding cost per tree is $0.12 (=$18/150 trees). The manufacturer also estimates that the cost of labor and equipment ranges from $0.90 to $1.50 per tree, so this study uses the average of that range, which is $1.20 per tree. Columns 3 through 6 in Table 1 show the cost estimates of the compound, injector, labor and total cost on a per tree basis for different tree trunk sizes. Columns 7 through 10 show the cost estimates for the same categories but on a per acre basis (assuming a tree density of 150 trees per acre).
For trees that are in good condition and have a full canopy, the compound concentration doubles to 11,000 ppm. The estimates for the total cost by trunk diameter are shown in Table 1, but the reader needs to look one size up in diameter because as shown in column 2 of Table 1, the compound volume doubles as the diameter size increases to the next category. Thus, for example, the cost for treating a healthy tree with a trunk diameter of 2.125 to 3 inches would be $1.38 per tree, which would translate into $207.58 per acre (assuming 150 trees per acre). The only value missing in Table 1 is that for trees that are more than 6 inches in diameter. For such trees, the cost per tree would be $1.70, which would translate into $255.49 per acre.
According to the Florida Department of Citrus (FDOC) final field box report for 2022–23, the average delivered-in price for processed Valencia oranges was $3.29 per pound solids, and yield was 5.09 pound solids per box, resulting in a delivered-in price per box of $16.71. The cost of picking and hauling Valencia oranges in 2022–23 is estimated at $4.46 per box, while the FDOC assessment was $0.12 per box. It can then be estimated that the average on-tree price for processed Valencia oranges during 2022–23 was $12.13 per box.
Dividing the total cost per acre estimates in column 10 of Table 1 by the on-tree price gives estimates of the yield response per acre growers need to obtain to offset the annual cost of injecting trees with oxytetracycline. Table 2 shows such estimates by tree trunk sizes; the additional number of boxes needed ranges from 16.7 to 18.7 per acre. Column 3 of Table 2 also shows that such an increase in yield would represent a 33% to 37% increase relative to the statewide (average) yield for Valencia oranges in 2022–23 (which is 51 boxes per acre). One of the manufacturers stated that “it is not uncommon to see a 30% to 35% yield benefit in year one.”
If a grower has a yield of 51 boxes per acre, and the manufacturer’s stated benefit is achieved, Table 2 shows that the additional yield would only allow the grower to offset the cost of the treatment. Regarding year two, the same manufacturer stated that the yield benefit can be as high as 60%. If such an outcome is realized — and, importantly, prices stay at a similarly high level next season — about half of that benefit would be needed to pay for the treatment in the second season, and only the remainder would translate into profit.
However, in Table 2, columns 4, 5 and 6 show the percent increase that the number of boxes in column 2 would represent when a grower has a yield of 100, 150 and 200 boxes per acre, respectively. At such yield, and if the expected yield response stated by the manufacturer is realized, the treatment may be profitable in both the first and second year.
Cost estimates are used to address the question of what yield response would be needed for injecting trees with oxytetracycline to be an economically viable treatment for growers to adopt. It was found that if the grower’s yield is equal to the statewide (average) yield for Valencia oranges, the expected additional yield would only allow the grower to offset the cost of the treatment in the first year but may result in a profit in the second year. If the grower’s yield is higher than the state average, the treatment may be profitable in both the first and second year. Importantly, however, this analysis does not consider the potential long-term negative impact that injecting trees may have.
Ariel Singerman is an associate professor and Extension economist at the University of Florida Institute of Food and Agricultural Sciences Citrus Research and Education Center in Lake Alfred.
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