Considerations When HLB-Resistant Trees Arrive

The development of citrus varieties that can resist HLB could eventually change how growers manage the disease. However, a recent study suggests the transition may not be as simple as planting resistant trees and stopping control of the Asian citrus psyllid (ACP) that spreads HLB.

A paper about the research, published in the April 2026 issue of Agricultural Systems, examines how growers might respond economically when HLB-resistant citrus cultivars become available. The paper — “How Resistant Cultivars Reshape Disease Management: An Application to Citrus Greening Disease” — was written by Xiurui Cui and Zhengfei Guan of the University of Florida and Kelly A. Grogan of the University of Wyoming.

The researchers developed a computer-based economic model that considered two major decisions:

1. When a grower would replace an existing grove with a resistant cultivar
2. When the grower would stop controlling the ACP

One important finding is that growers may not immediately replace productive trees when resistant varieties become available. Because citrus is a perennial crop, removing an existing grove means giving up production while new trees become established. The best timing for replanting depends on factors such as tree age, grove density and the effectiveness of the resistant cultivar.

The study identified a particularly important benchmark of 90% resistance efficacy. In the researchers’ model, when a cultivar provided at least 90% protection against HLB, it became economically beneficial for growers to stop insecticide applications for psyllid control before replanting with the resistant trees. With lower levels of resistance, continuing psyllid control remained economically valuable.

The research reinforces that resistant or tolerant trees could become an important long-term HLB management tool, but they are unlikely to eliminate the need for other management practices immediately.

The transition also could affect neighboring groves. If some growers stop psyllid control while others continue managing older, susceptible trees, increased psyllid pressure could create problems for growers who have not yet replanted.

The researchers conclude that successful adoption of resistant cultivars will require looking beyond individual groves and considering how management decisions affect the broader citrus-growing region.

Read the paper here.