Eastern Hemlock Looper Research Articles

FATTY ACID COMPOSITION AND LIPID CONTENT OF LATE LARVAL AND PUPAL STAGES OF THE EASTERN HEMLOCK LOOPER, LAMBDINA FISCELLARIA FISCELLARIA (LEPIDOPTERA: GEOMETRIDAE)

AbstractA total of 14 known fatty acids and one unknown fatty acid were detected in the third instar, fourth instar, prepupa, and female and male pupae of the eastern hemlock looper, Lambdina fiscellaria fiscellaria. The C8:0,3 C10:0, C22:1, and C24:0 fatty acids and an unknown fatty acid were not detected in the third instar larvae, and the unknown was also absent from the fourth instar larvae. The C24:0 fatty acid was absent from the prepupae and both the male and female pupae. The C22:1 fatty acid was absent from the prepupae. Otherwise, developmental stages contained the C8:0, C10:0, C14:0, C15:0, C16:0, C18:0, C18:1, C18:2, C18:3,C20:0, C20:1, C22:0, C22:1, and the C24:0 fatty acids and the unknown fatty acid. In general, the level of a given fatty acid decreased with succeeding developmental stages. The lipid level was also determined for each developmental stage.

Regeneration of protoplasts of Entomophthora egressa, a fungal pathogen of the eastern hemlock looper

The regeneration patterns for protoplasts of Entomophthora egressa MacLeod and Tyrrell grown on modified Grace's insect tissue culture medium supplemented with fetal calf serum (a highly modified version of Grace's medium lacking serum and more closely approximating the hemolymph of the eastern hemlock looper), Müller-Kögler's coagulated egg yolk medium supplemented with Tristearin, and water agar are documented. Protoplasts on liquid and egg yolk media had varying degrees of common developmental patterns. On liquid media, development involving prophyphal spheres and fusion spheres predominated. Hyphae emerged from the prohyphal spheres; however, the fusion spheres did not develop further. On the coagulated egg yolk medium, the individual, non-chain, cells coalesced and developed into pleomorphs which later developed into osmotic shock-resistant postprotoplasts. A postprotoplast gave rise to a hypha which produced a terminal conidium. Later resting spores were detected. Water agar supported scant mycelial growth as compared with that on coagulated egg yolk but more than that on the liquid media. Solid substrates appeared to favor mycelial development. Regeneration could be avoided by the addition of fresh Grace's modified medium to either coagulated egg yolk plates or to cultures with Grace's modified medium. Obtaining protoplasts from hyphae and the reversion of these protoplasts to form hyphae appeared to be a fixed property of E. egressa.This report is believed to be the first for reversion of protoplasts initially produced by non-enzymic means.

A COLLECTING METHOD FOR PUPAE OF LAMBDINA FISCELLARIA FISCELLARIA (LEPIDOPTERA: GEOMETRIDAE)

AbstractThree types of traps were tested in 1969 and 1970 for collecting pupae of the eastern hemlock looper, Lambdina fiscellaria fiscellaria (Guen.). Highest numbers of pupae were obtained with burlap traps made from 2-ft-wide bands wrapped around trunks of infested trees. The proportion of the pupae in the burlap traps was estimated. Some of the potential uses for pupae collected by the method are mentioned.

TWO SPECIES OF ENTOMOPHTHORA PATHOGENIC TO THE EASTERN HEMLOCK LOOPER (LEPIDOPTERA: GEOMETRIDAE) IN NEWFOUNDLAND

AbstractTwo fungi, Entomophthora sphaerosperma and E. egressa, were collected and identified from larvae of the eastern hemlock looper, Lambdina f. fiscellaria (Guen.), in Newfoundland. These two fungi appear to play the most important role in the decline of looper infestations. Field trials indicate that the disease can be transmitted from laboratory-reared larvae artificially infected with the protoplast stage of E. egressa, to uninfected larvae. This suggests that infection may be established artificially within a population of the looper prior to the ’natural’ occurrence of the epizootic.

A METHOD FOR REARING OVERWINTERING LARVAE OF WINTHEMIA OCCIDENTIS (DIPTERA: TACHINIDAE), A PARASITE OF THE EASTERN HEMLOCK LOOPER

AbstractWinthemia occidentis Rhn. was introduced into Newfoundland to strengthen the parasite complex of the eastern hemlock looper. This tachinid has two emergence periods, one in the fall, the other in the following spring. A method was developed for rearing overwintering tachinid larvae to the adult stage. The best rearing results were obtained when the larvae were stored outdoors in jars of peat moss for the fall and winter period and removed to controlled temperature and humidity conditions in the spring, to complete development.

Spontaneous formation of protoplasts by a species of Entomophthora

Conidia of a species of Entomophthora isolated from the eastern hemlock looper, Lambdina fiscellaria fiscellaria, were germinated in Grace's insect tissue culture medium. Two germ tubes were normally formed per conidium, and when these reached a length of approximately 100–150 μ, the protoplasm was spontaneously released from the tip of the germ tube as a viable protoplast. The subsequent development of the protoplast is described. Two-day-old protoplasts were highly pathogenic to a number of lepidopterous larvae upon intrahemocoelic injection, death of the insects ensuing within 4–5 days. The Entomophthora species could be reisolated from the killed insects.

An ultrastructural study of the development of a nuclear polyhedrosis virus of the eastern hemlock looper, Lambdina fiscellaria fiscellaria.

The development of a nuclear polyhedrosis virus of the eastern hemlock looper, Lambdina fiscellaria fiscellaria, is described in gut and hypodermal tissues. Infection was found in the midgut cells where a cycle of virus replication occurred but no polyhedron formation was observed. In the hypodermis the mode of viral development was similar to that recorded for other nuclear polyhedroses which have bundles of virions surrounded by membranes and occluded in polyhedra. At an advanced stage of infection, non-occluded virions formed regular arrays in some of the infected nuclei. Other non-occluded virions were found in the cytoplasm and in large numbers near the periphery of cells. Angular cytoplasmic inclusion bodies showing the structure of polyhedron protein, but containing no virions, were associated with virus-infected cells in both the tissues examined.

PATHOGENICITY TESTS OF NUCLEAR POLYHEDROSIS VIRUSES INFECTING THE EASTERN HEMLOCK LOOPER, LAMBDINA FISCELLARIA FISCELLARIA (LEPIDOPTERA: GEOMETRIDAE)

AbstractLarvae of the eastern hemlock looper, Lambdina fiscellaria fiscellaria (Guen.), are susceptible to a nuclear polyhedrosis virus as well as nuclear polyhedrosis viruses isolated from the western hemlock looper, L. f. lugubrosa (Hulst), and the western oak looper, L. f. somniaria (Hulst). The pathogenicity of these viruses was similar when tested on eastern hemlock looper larvae and it is suggested that the same virus infects the three subspecies. Resistance to the virus did not increase with age; second-, third-, and fourth-instar larvae were equally susceptible. The period from ingestion to death varied with concentration of virus and rearing temperature. Results of pathogenicity tests are given.

The effect of storage on the nuclear polyhedrosis virus of the eastern hemlock looper, Lambdina fiscellaria fiscellaria (Lepidoptera: Geometridae)

Bundles of virions disappeared from polyhedra of the eastern hemlock looper nuclear polyhedrosis virus stored for 6 years at 4°C. Holes were left in the polyhedra, and the pathogenicity of the virus was greatly reduced. Freeze-drying may be a better method of storing the virus.