By Lauren Diepenbrock
Recently, several articles have highlighted a potential new threat to the citrus industry in Florida, the lime swallowtail. While it is true that this pest has been found in residential citrus plantings in Key West, it is unlikely that lime swallowtail will have much of an impact, if any, on Florida’s commercial citrus industry.
Lime swallowtail is native to the Middle East and southern China. It also occurs in the Caribbean region, having been found in Cuba, Hispaniola, Puerto Rico, the Virgin Islands, Jamaica and the Cayman Islands. Due to the proximity of populations on neighboring islands, it was not a surprise that lime swallowtail eventually found its way to Florida, likely blown in with tropical storms or hurricanes.
In its native regions, lime swallowtail has a history of being a pest of open-field citrus nurseries, causing complete defoliation of nursery trees. In Florida, however, citrus may only be propagated in approved, enclosed structures (Section 5B-62.007, Florida Administrative Code), thereby reducing the likelihood of a large insect pest, such as a swallowtail butterfly, from accessing trees to lay eggs and enable their offspring to cause damage.
DAMAGE AND LIFE STAGES
Damage from lime swallowtails is caused by their juvenile stages, caterpillars, which feed on leaves of plants in the family Rutaceae, which includes citrus, and in some regions of the world, Fabaceae, which includes various species of peas. In Key West, both damage and juvenile life stages including eggs and caterpillars have only been found on citrus in residential settings.
The eggs and early caterpillar stages are almost indecipherable from the eggs and caterpillars of the native giant swallowtail, whose caterpillars are commonly referred to as orangedogs. Caterpillars of both swallowtails have a defensive organ, called the osmeterium, that they can inflate from near their heads to deter predators. This organ looks like orange to red horns and has a faint odor that is used as a repellent. The final caterpillar developmental stage of lime swallowtail turns a bright green and is easily camouflaged by citrus leaves. The adults are stunning and appear much different from native giant swallowtails (see images).
While the lime swallowtail is not anticipated to be a problem for commercial citrus growers, the caterpillars, just like orangedogs, will consume large quantities of leaf tissue which may be problematic for young trees and small plantings in residential settings. The easiest option to manage the caterpillars of either swallowtail species in small plantings is to inspect citrus trees often. Remove and destroy eggs and caterpillars found on citrus trees in a bowl of soapy water. For commercial growers, this caterpillar should be managed similarly to the orangedog if management is required (see Florida Citrus Production Guide).
The Florida Department of Agriculture and Consumer Services (FDACS) Division of Plant Industry is currently working on a local eradication campaign in Key West. If you suspect that you have an infestation of lime swallowtail, please collect them, place them in a sealed container, and contact the FDACS helpline at 888-397-1517 or DPIHelpline@FDACS.gov or contact your local University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) Extension office.
Get more information on lime swallowtail from the UF/IFAS Electronic Data Information Source and FDACS.
Lauren Diepenbrock is an assistant professor at the UF/IFAS Citrus Research and Education Center in Lake Alfred.
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