What you need to know about the avocado lace bug

January 03 , 2022

The content of this article 'What you need to know about the avocado lace bug' was prepared by F.W. Mead and J.E. Peña at the University of Florida and has been revised and republished by FreshFruitPortal.com.

The avocado lace bug, Pseudacysta perseae (Heidemann) (Figure 1), was originally described in 1908 as Acysta perseae from Florida specimens.

Blatchley (1926) stated that Acysta perseae differed widely from Acysta spp. of Champion (1898). Blatchley described the genus Pseudacysta for Acysta perseae.

For most of the years since its description, the avocado lace bug was regarded as having limited distribution, primarily to peninsular Florida, and being of only occasional minor economic importance.

However, the number of complaints about its damage to avocado leaves, Persea americana P. Mill., has increased.

Figure 1. Adult and nymphs of the avocado lace bug, Pseudacysta perseae (Heidemann).

Figure 1. Adult and nymphs of the avocado lace bug, Pseudacysta perseae (Heidemann). Credit: James Castner, University of Florida

Distribution

The known distribution of Pseudacysta perseae includes the Caribbean, Mexico, Guatemala, Venezuela, and French Guyana. In the United States, it is found in California and the southeastern states (Humeres et al. 2009b).

Identification

The most complete description of adults and late instar nymphs was by Heidemann (1908). Medina-Gaud, Segarra-Carmona, and Franqui (1991) gave a shorter version of Heidemann's description.

Blatchley (1926) described adults as 2 mm long and oblong-oval shaped. The body beneath, head, pronotum (except for the front edge and tips of the posterior third), and a bar crossing the basal third of elytra, but reaching only slightly outside of the discoidal area, are piceous-brown or blackish; the remainder of the upper surface is yellowish-white (we have seen numerous specimens with elytra tawnier in color, being orangish at basal area); legs and antennae are pale yellow, the claws and apical half of fourth antennal segment are blackish.

The pronotum is sub-pentagonal, with front side margins obtuse and converging strongly toward the apex; the posterior portion is flat, triangular, and acutely pointed; the disc is finely and densely punctuated and with a single entire, low, median carina. Elytra are much surpassing the abdomen, their tips broadly rounded; and the discoidal area is long, narrow, and not closed behind.

Heidemann (1908) illustrated both nymphs and adult forms. Medina-Gaud (1991) included color photographs of adults, nymphs, eggs (Figure 2), and leaf damage. Beshear et al. (1976) published a photograph of an adult museum specimen.

Wolfenbarger (1963), in one photograph, illustrated nymphs, adults, eggs, and excrement on the underside of an avocado leaf. Moznette (1922) provided an excellent drawing of the adult.

Figure 2. Eggs of the avocado lace bug, Pseudacysta perseae (Heidemann).

Figure 2. Eggs of the avocado lace bug, Pseudacysta perseae (Heidemann). Credit: Adrian Hunsberger, University of Florida

Pseudacysta perseae is the only described species in this genus, so identification to genus is tantamount to the specific level.

Blatchley (1926) described the genus Pseudacysta and provided keys to the Tingidae of the eastern United States. Hurd (l946) provided a key to the lace bug genera of North America. Brailovsky and Torre (1985) re-described Pseudacysta and mentioned that it was a pest on avocado in Mexico.

They commented that Pseudacysta is characterized by the reduction of the paranotum, confined to the humeral angles, and formed by one or two small cells, and by a discoidal area open apically.

Acysta was cited as having the discoidal area closed in its posterior end and by having a more developed paranotum. The paranota of Pseudacysta are present only as small ear-like flaps on humeri.

Hosts

Known hosts include:

avocado, Persea americana P. Mill.,
camphor, Cinnamomum camphora (L.) J. Presl. and
red bay, Persea borbonia (L.) Spreng.

Heidemann (1908) in his original description listed Persea carolinensis and Persea gratissima as hosts of specimens collected in Florida. Persea carolinensis is a synonym of swamp red bay, Persea palustris (Raf.) Sarg.

References differ as to whether Pseudacysta palustris is a valid species. We follow Kartesz and Kartesz (1980) in which Pseudacysta palustris is listed as a synonym of Pseudacysta borbonia.

Persea grattissima Gaertn. F. is a synonym of Pseudacysta americana. In the northern part of peninsula Florida and other parts of the Deep South, camphor is the main host. Avocado is the main host in the southern coastal region of Florida.

Figure 3. Leaf damage caused by the avocado lace bug, Pseudacysta perseae (Heidemann).

Figure 3. Leaf damage caused by the avocado lace bug, Pseudacysta perseae (Heidemann). Credit: James Castner, University of Florida

Bionomics

The life cycle of Pseudacysta perseae was reported by Abud Antum (1991) to be 22 days from egg to adult stage. Moznette (1922) reported that this lace bug confines its attacks to the lower surface of the foliage, where it feeds by extracting the juices from the plant. It usually lives in colonies, depositing eggs upright in irregular rows in clusters on the lower leaf surface.

The extraction of the juices from the foliage causes gradual, localized destruction of the plant cells. The resulting chlorotic areas correspond to the location of the lace bugs below.

Where a colony of these insects is present, the eggs and the lower surface of the leaf are more or less thickly covered by a dark, sticky secretion from the insects. The principal injury, however, is the destruction of the leaf cells due to the sucking habit of the insects.

Wolfenbarger (1963) reported an instance of avocado trees in one Florida grove becoming defoliated and stated that during the previous decade, avocados were rarely infested with lace bugs.

Wolfe et al. (1949) stated that it preferred the West Indian "race" of avocado, although no variety was known to be free from attack. There are 42 records of the avocado lace bug in the Florida State Collection of Arthropods (FSCA), and 29 of these have been since 1983.

This bug is becoming a problem in Florida, but not nearly to the extent as it is in the Dominican Republic, for instance, where whole trees have been defoliated by it.

Wolfe et al. (1949) reported that this lace bug was found occasionally infesting the underside of leaves in winter, but more often it was found in the warmer, dry spring months.

There are no May records of Pseudacysta perseae in the FSCA, but all other months have adult records, and most have nymphal collections. Both nymphs and adults have been reported several times during the winter months in southern Florida, but we have very few nymphal and adult records during winter in northern Florida.

Brown necrotic areas on avocado leaves (Figure 3) are frequently associated with lace bugs. Freshly affected leaves from the Homestead, Florida area were analyzed by Dr. Timothy Schubert, Plant Pathologist, FDACS, Gainesville (personal communication).

He suggested that injuries from lace bug activities provided the infection court for the anthracnose fungus, Colletotrichum gloeosporioides, the cause of the large necrotic blotches on the leaves, that first catches attention when surveying avocado and other hosts.

The anthracnose pathogen was isolated consistently from the advancing margins of the necrosis surrounding the lace bug colonies. Schubert added that dendritic necrotic patterns were due to infections by powdery mildew, Oidium sp.

Detection

Yellowish or brownish necrotic areas, either above or below the leaf, are indications of the presence of avocado lace bugs underneath. Black pepper-like objects, centered in the brown patches usually are eggs covered with a black, sticky substance, sometimes moldy.

Also, on the underside look for black specks of excreta, cast skins, nymphs, and adults, no longer than 2 mm. For identification, place a few infested leaves and a paper towel in a plastic bag, tie securely, and ship in a mailing tube with collection data.

Management

All insecticides registered for use on avocado provide control of the lace bugs (J.E. Pena, unpublished data). Sprays should be directed to the underside of leaves and repeated at approximately two-week intervals until control is achieved.

Abud Antun (1991) reported that the most important predator of the avocado lace bug in the Dominican Republic is the thrips, Frankliniella vespiformis (Crawford).

Source: University of Florida