Florida Department of Agriculture and Consumer Services

Citrus Greening and Honey Bees

Contact Us

Pollinator Protection Outreach:
Brandi Simmons
(352) 395-4828 (Office)
Brandi.Simmons@FreshFromFlorida.com

Apiary Inspection:
David Westervelt
(352) 395-4636

Pesticide Licensing and Registration:
Sarah Oglesby
(850) 617-7997

The management strategy for citrus greening proposed by the University of Florida and the citrus industry requires the identification and removal of infected trees, propagation of disease-free nursery stock, and management of the Asian citrus psyllid, the vector of the citrus greening pathogen. Since citrus greening and the psyllids are permanently established in Florida citrus, the goal of psyllid management is suppression of psyllid populations to as low a level as possible, as eradication of the insect or pathogen is deemed no longer possible.

The suppression of psyllid populations may require an increased use of insecticides, both soil- and foliar-applied, many of which are toxic to honey bees. Therefore, it is important for beekeepers to understand how these products are typically used.

For the most up-to-date information about citrus greening and its management, visit the Florida Department of Agriculture and Consumer Services' (FDACS) Division of Plant Industry.

Soil-Applied Neonicotinoids

Young citrus trees produce multiple and sometimes unpredictable flushes of growth throughout the year and, therefore, are particularly vulnerable to becoming infected with citrus greening before they reach production age. (Female citrus psyllids lay their eggs on new growth, and the nymphs can feed only on soft, young leaf tissue.) For these young trees (up to 5 years old or 9 feet tall), a regimen of soil-applied systemic neonicotinoids may be used to provide year-long protection. 

Currently, three soil-applied neonicotinoid insecticide active ingredients (clothianidin, imidacloprid and thiamethoxam) are available for use on young bearing trees. The current Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) Section 3 label rates for products containing these active ingredients are adequate to protect smaller immature (less than 3 years old, less than 5 feet tall) citrus trees, but additional applications are needed to protect bearing trees between 3 and 5 years old (approximately 5 to 9 feet tall). 

In response to requests from the citrus industry, FDACS accepted a Special Local Need (SLN or Section 24c) registration that allows for doubling the maximum amount of imidacloprid that can be applied in a year. More importantly, this SLN effectively allows growers to make a second application per year to trees in the critical size range of 3 to 5 years old (5 to 9 feet tall). A similar action was taken to approve the use of Belay Insecticide, containing clothianidin, under FIFRA's Section 18 provision, to allow a doubling of the annual limit and a second application in a 12-month period.

The imidacloprid SLN and the clothianidin Section 18 were the first of two registration actions taken to address the need for year-long control of disease transmission in new replants, as well as trees 3 to 5 years old. These two active ingredients combined with an application of soil-applied thiamethoxam provide the year-long protection spoken of previously.

As with any pesticide, increased use can lead to an increased potential risk to human health and non-target organisms, including managed bee colonies. For these active ingredients, FDACS determined that potential impacts to bees are the driving risks of significant concern. After a thorough review of available literature and consultation with the U.S. Environmental Protection Agency (EPA), FDACS issued the SLN and Section 18 and began identifying additional ways (outside of the label) that the risks to bees could be mitigated.

Limiting Impacts to Bees from Soil-Applied Neonicotinoids

FDACS, EPA, and the University of Florida agree that the primary risk to honey bees from soil application of neonicotinoids to citrus is associated with the potential consumption of pesticide residues in nectar and pollen. The method of direct application to the ground minimizes the potential for insecticide residues on the leaf or flower surface.

Impacts of exposure could include impaired feeding, disorientation and failure to return to the colony. An increased loss of returning foragers beyond the normal foraging mortality could impact overall colony health. Regarding the labels for the neonicotinoids, the SLN and the Section 18 labels restrict applications during bloom and limit the applications to trees 3 to 5 years old and younger. These trees represent only 7 percent of the total citrus acreage in Florida and do not bloom as comprehensively as more mature trees. In short, where blossom-laden (more than 5 years old) trees predominate, bees would be more apt to forage on these larger trees, which could reduce the opportunity for impacts to the hive.

Foliar Insecticides

Once trees reach 9 feet in height and are near maturity, soil-applied neonicotinoids are no longer effective for control of citrus psyllids due to the increased biomass of the tree and the label limits. For mature trees, currently, the only effective means of controlling psyllid populations is the use of foliar-applied insecticides.

Foliar insecticides are used to provide a quick knockdown of psyllid populations to prevent further spread of the disease. They may also be used on younger trees as a pesticide resistance management tool. Many of the foliar-applied products do not provide long-term, residual control. Most applications are made prior to or during “new flush” (new leaf growth) to protect against egg-laying psyllids and development of psyllid nymphs. Additional control strategies, however, are effective or required for immature (mostly nonbearing) and less mature, bearing trees. 

Limiting Impacts to Bees from Foliar-Applied Insecticides

Foliar applications of insecticides for Asian citrus psyllid suppression can be made throughout the growing season using ground and aerial equipment. 

Insecticides that are toxic to bees by either direct contact with spray or through contact with residues on foliage have label restrictions that may prohibit or restrict application during or prior to citrus bloom. Overall, these restrictions should be adequate to limit impacts to bees during citrus bloom.

However, it is increasingly important for beekeepers to be aware of the citrus management practices in areas where they place their hives and to reach out to area growers. FDACS also encourages beekeepers to provide their apiary locations and timing to the Ag-Apiary Mapping System so that citrus growers and grove managers can check the map to see when and where apiaries may be located relative to their grove. This may allow for better communication to reduce the risk of unintended pesticide exposures.