Researchers examine nutrient costs for HLB-infected trees

03/21/2014 11:04:00 AM
Bob Rouse and Fritz Roka


Nutrient treatments pay

Five year cumulated totals of production, material costs, and net income above foliar material costs are summarized in Figure 1. Treatment 2 produced more than 1,300 boxes with a foliar mix of macro- and micro nutrients along with phosphorous acid. 

The control treatment (#10), a grower standard before the advent of greening, produced only 468 boxes during the five-year study period. The most expensive treatment was #1, the Boyd Mix, costing nearly $550 per acre of material costs each year.

Multiplying annual costs by five years and subtracting from fruit revenue provides an estimate of cumulative gain in grower income. To estimate fruit revenues, one needs to make some assumptions about pound solids, delivered-in fruit prices and harvesting costs.

In our example, we assumed that every box of Hamlins produced 5.6 pound-solids per box and that the grower would receive a delivered-in price of $1.70 per pound solids.

Pick, roadside and haul costs were assumed to be $3 per box. Treatments 4, 2 and 7 generated the most income above foliar material costs. Treatment 4 generated nearly $6,900 of cumulative income, or nearly $4,500 more income than the control treatment (#10). Returns increased by $6,521 and $6,015 for treatments 2 and 7, respectively.


Dr. Bob Rouse is an associate professor of citrus horticulture at the Southwest Research and Education Center in Immokalee. He can be reached at or 239-658-3400. Dr. Fritz Roka is an associate professor and economist in the Food and Resource Economics Department based at the SWFREC. He can be reached at


Table 1. Projected cumulative production over 5 years by treatment.

Treatment Rank by Production

Cumulative production

Treatment #


box/ac (5 years)



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