NC State Extension Publications

Description and Biology

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The red bay triozid scientific name, Trioza magnoliae, was misnamed as this insect only infests bays in the genus Persea not sweet bay or other magnolias. Eggs have not been described. Young nymphs are yellow and flat. Mature nymphs are green with orange wing pads, red eyes, and short black antennae and sparse waxy filaments. Adults are pale greenish-yellow, about 1/8 inch long, and resemble miniature cicadas. It was speculated that eggs are laid under the epidermis of leaves. However, it may be that the new females lay their eggs inside leaf buds much like the related boxwood psyllid does. If this is true, the insect could spend the rest of the summer, fall, and winter inside red bay buds as eggs that hatch as plant growth resumes. As newly hatched nymphs begin to feed, the margin of the leaf begins to curl and ultimately completely envelops nymphs in a swollen, elongated, pocket-like gall. The galls may be over 1/2 inch long. When the triozid nymphs are mature, the gall splits along the edge to release them. The cast skins can be seen on the lower leaf surface. In Florida, adults seem to have a peak emergence in mid-May with at least three overlapping generations. If bays have more than one flush of growth in North Carolina, it is likely that a new generation will develop on each new flush.

Host Plants

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The red bay triozid infests red bay, silk bay, and swamp bay. Leaves attacked just as they are opening may be severely distorted. There may be one to eight galls per leaf, and up to 80% of the foliage may have galls. However, even heavy infestations cause little real damage to the health of infested bays.

Red bay triozid galls

Red bay triozid galls are alarming but harmless to the overall health of red bay.

Residential Recommendations

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In spite red bay triozid nymphs living inside a gall, they may be parasitized by tiny wasps. Parasitized nymphs turn dark. A midge also preys on red bay triozid nymphs. Birds have also been observed opening the galls to feed on the nymphs. Because the galls can only develop only on new, developing leaves, controlling the very young triozids should stop gall development. Spraying with a neem seed extract or with a synthetic systemic insecticide at bud break should protect the new leaves from the developing triozid nymphs. Systemic insecticides such as acephate (Orthene) and imidacloprid shoould also be effective. All three of these insecticides should be available in the plant centers of big box stores. Imidacloprid can also be applied to the soil under red bays unless there is a well or open water nearby.

Eulophid wasp

Eulophid wasps are teeny-weeny and harmless to people but deadly to red bay triozids.

Author

Professor Emeritus
Entomology & Plant Pathology

Publication date: Feb. 19, 2020
Revised: Feb. 19, 2020

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