Magnolia Leaf-Footed Bug

Scientific name: Leptoglossus fulvicornis (Westwood 1842)

Order: Hemiptera (true bugs)

Family: Coreidae (leaf-footed and squash bugs)

Description

Magnolia leaf-footed bug adults are uniformly dark brown with lighter brown antennae, front, and mid-legs. They lack a transverse white stripe found in similar species, such as the western conifer seed bug (L. occidentalis) (Figure 1b). Magnolia leaf-footed bugs may be confused with Leptoglossus oppositus, which are also uniformly dark brown (Figure 1c); however, magnolia leaf-footed bugs can be distinguished by the presence of flaring, dentate pronotal margins (larger "shoulders") and less scalloped hind tibial margins. Squash bugs, which are other commonly encountered coreids, completely lack wide, leaf-life tibial margins (Figure 1d).

Figure 1. Magnolia leaf-footed bug and look-alikes. 1a) Magnolia leaf-footed bug. 1b) Western conifer seed bug. 1c) Leptoglossus oppositus (no common name). 1d) Squash bug

Distribution

Magnolia leaf-footed bugs are found throughout eastern North America, from Ontario and Massachusetts, south through Florida, west to West Virginia, Arkansas, and Texas. Magnolia leaf-footed bugs are more common and abundant in the southern portions of the range (Wheeler & Miller 1990, Chordas et al. 2005, BugGuide 2017). Suggestions have been made that the range of species is expanding westward, although it is unclear if this is due to true movement by the bugs or an artifact of collection bias as native magnolias occur in Arkansas and Texas. Overwintering adults have not been found north of Pennsylvania, so it is unclear if permanent breeding populations exist in the northern portions of the range; it has been suggested that they may migrate north and survive only mild winters, or perhaps overwinter only along the coast of northern states (Wheeler & Miller 1990).

Hosts

Magnolia leaf-footed bugs feed exclusively on Magnolia species and have specifically been recorded from the following species: M. acuminate (cucumber tree), M. kobus (Kobus magnolia), M. grandiflora (southern magnolia), M. heptapeta (yulan), M. macrophylla (large-leaved cucumber tree), M. stellate (star magnolia) M. tripetala (umbrella tree) M. virginiana (sweetbay), M. × loebneri, M. × soulangeana (saucer magnolia). Most specimens have been collected from magnolia planted in ornamental settings, although the species likely occurs on native species endemic to the southeastern United States. Adults and nymphs have rarely been found on other trees, including Prunus armeniaca (Russian apricot) and Quercus imbricaria (shingle oak), although it is doubtful they can successfully reproduce off of magnolia.

Life history and behavior

Magnolia leaf-footed bugs overwinter as adults in leaf litter around the base of magnolia trees. They become active when small fruits begin to appear on magnolia trees, which is as early as late April in the southeastern US, late May in Tennessee and mid-June to early July in Pennsylvania. Eggs are laid in a chain (usually single, rarely double) on the leaves, usually on the underside along the rib (Figure 2) but sometimes near the leaf edge on either surface. Average clutch size ranges from 20–27 eggs (Mitchell & Mitchell 1983, Wheeler & Miller 1990). First and second instar nymphs are most commonly found in circular aggregations on the egg masses and leaves, while later instars and adults are most commonly found on the fruits.

Figure 2. Magnolia leaf-footed bug eggs on a leaf. From Wheeler & Miller (1990), used with permission.

Damage to trees

First instar nymphs do not feed. Older nymphs and adults feed on developing fruit and mature seeds by piercing them with their elongate mouthparts. Feeding causes spotting and pitting on the seeds (Figure 3), but does not appear to affect the overall health of the tree. In addition to feeding damage, patches of black, shiny excrement can be found on the leaves of infested trees (Figure 4).

Figure 3. Damage to magnolia seeds.

Figure 4. Magnolia leaf-footed bug excrement on the underside of a leaf. From Wheeler & Miller (1990), used with permission.

Threat to human health

Magnolia leaf-footed bugs only feed and develop on magnolia, so will not bite humans and do not pose a threat to human health. In the highly unlikely event that a magnolia leaf-footed bug mistakenly bites a person, the reaction would likely be similar to a bite from the related western conifer seed bug, Leptoglossus occidentalis, from which single accidental bite is recorded: a sudden and intense localized pain during the bite, followed by a red lesion or welt that slowly fades over the course of a few weeks (Hornok & Kontschán 2017).

Control

Eggs of magnolia leaf-footed bugs are parasitized by the parasitoid wasps Gyron carinatifrons and G. pennsylvanicum, both of which are known to parasitize other Leptoglossus and coreids. Only one study examined egg parasitism of Gyron pennsylvanicum in magnolia leaf-footed bug and found that 77% of egg masses and 31% of total eggs were parasitized (Mitchell & Mitchell 1983); however, G. pennsylvanicum can parasitize 75–100% of the eggs of western conifer seed bug (Roversi et al. 2014), so parasitism rates of magnolia leaf-footed bug, may be substantially higher. Parasitic fly eggs have been recorded on adult magnolia leaf-footed bugs, but have not been reared for identification; Trichopoda pennipes has been recorded from L. occidentalis and L. oppositus (Morrill 1910, Ridge-O'Connor 2001), so it seems likely that it also attacks L. fulvicornis.

Because magnolia leaf-footed bug does not affect the health of magnolia trees and hosts a number of different parasitoids, control is generally not necessary. If control is still desired, a few non-chemical options may be effective. First, early instars, which cannot fly, can be knocked off of magnolia leaves with a strong jet of water. Adults may be controlled by removing and disposing of leaf litter from around magnolia trees during the fall and spring before they emerge.

Unless otherwise cited, information is derived largely from Wheeler & Miller's (1990) definitive work on Leptoglossus fulvicornis.

Authored by Michael Skvarla, Insect Identification Laboratory Director & Extension Educator, January 2018.

References

Chordas, S. W., III, H. W. Robison, E. G. Chapman, B. G. Crump, and P. W. Kovarik. 2005. Fifty-four state records of true bugs (Hemiptera: Heteroptera) from Arkansas. Journal of the Arkansas Academy of Science, 59: 43–50.

BugGuide. 2017. Leptoglossus fulvicornis. Accessed 30 January 2017.

Hornok, S., and J. Kontschán. 2017. The western conifer seed bug (Hemiptera: Coreidae) has the potential to bite humans. Journal of Medical Entomology, 54(4): 1073–1075.

Mitchell, P. L., and F. L. Mitchell. 1983. Range extension of Leptoglossus fulvicornis with observations on egg parasitism. Southwestern Entomologist, 8: 150–153.

Morrill, A. W. 1910. Plant bugs injurious cotton bolls. USDA Bulletin 86. 110 pp.

Ridge-O'Connor, G. E. 2001. Distribution of the western conifer seed bug, Leptoglossus occidntalis Heidemann (Heteroptera: Coreidae) in Connecticut and parasitism by a tachinid fly, Trichopoda pennipes (F.) (Diptera: Tachinidae). Proceedings of the Entomological Society of Washington, 103: 364–366.

Rovers, P. F., G. Sabbatini Peverieri, M. Maltese, P. Furlan, W. B. Strong, and V. Caleca. Journal of Applied Entomology, 138: 27–35.

Wheeler, A. G., Jr., and G. L. Miller. 1990. Leptoglossus fulvicornis (Hemiptera: Coreidae), a specialist on magnolia fruits: Seasonal history, habits, and descriptions of immature stages. Annals of the Entomological Society of America, 83(4): 753–765.