If you have citrus in your landscape, be on the lookout. I get frequent calls this time of year about something strange, devouring citrus tree leaves. No, it’s not a fungus or bird droppings. Look closer, it moves! This unpleasant looking caterpillar will one day turn into a beautiful, exotic-looking butterfly.
The giant swallowtail is abundant in Florida and widely distributed throughout the American continent. All stages of the larva (caterpillar) have the appearance of bird droppings, but some stages are more realistic in imitating bird droppings (figure 1). The adult butterflies are truly giant, with an average forewing span of 14 cm for males and nearly 15 cm span for females. The dorsal wing surface is black with a yellow bar across the forewings. The ventral wings are primarily yellow (Figure 2). Adult butterflies sip nectar and can be found in gardens and flowering landscapes. Some of the giant swallowtail’s favorite nectar sources are azalea, honeysuckle, goldenrod and swamp milk weed. The larva, also known as, “orangedog” is considered a minor pest of citrus. Members of the citrus family are favorite host plants of the larva. In fact, larva can quickly defoliate small or young trees.
What about control measures for homeowners?
Mechanical control is the best method. This is accomplished by scouting and hand picking larva from young or patio citrus, and then displacing the larva far away. Mature dooryard citrus trees are large enough to combat some defoliation, so no worries there.
Biological control methods are evident at the pupae stage of the life cycle. Pupae are immobile, and this leads to parasitic insects attacks, especially by wasps. Larval stages appear to be more protected from natural predators due to being less visible (imitating bird droppings).
The larva also possesses an osmeterium, which is an orange or reddish Y-shaped gland, that is located behind the head. If attacked by small predators, the larva extrudes the gland and attempts to wipe it against the attacker. At that point, a glandular, highly noxious secretion is released as a repellent that is toxic to small predators, such as ants and spiders.
What about control methods for commercial operations?
Mature commercial citrus trees can withstand infestation by many larvae. However, nursery stock and young grove trees can be protected with Bt (Bacillus thuringiensis) or chemically by insecticides.
For more information contact the Gulf County Extension Office at 639-3200.
Supporting information for this article can be found in the UF/IFAS Extension EDIS publication, “Giant Swallowtail, Orangedog, Papilio cresphontes Cramer (Insecta: Lepidoptera: Papilionidae)” by H. J. McAuslane: https://edis.ifas.ufl.edu/pdffiles/IN/IN13400.pdf
UF/IFAS Extension is an Equal Opportunity Institution.