Louis A. Falcon

Temporal events in the invasion of the codling moth, Cydia pomonella, by a granulosis virus: an electron microscope study

Abstract The replication cycle of the granulosis virus of Cydia pomonella, the codling moth, was studied at the cellular and tissue level. Membranelike complexes were observed forming within the remnants of the nucleolus in the cytoplasm of infected cells. Differences in cell polarity relative to the sites of virus entry assembly and budding as well as differences in the temporal aspects of replication were observed between midgut, fat body, and epidermal cells. The progressive spread of virus throughout larval tissues was studied at 24, 32, 48, 56, and 72 hr postinfection. The basal lamina seemed to be an effective barrier for the release of budded progeny virus into the hemocoel and large numbers of budded virus were produced.

Mass production, infectivity, and field application studies with the entomogenous fungus Paecilomyces farinosus

Abstract Hyphal bodies (HB) of the entomogenous fungus Paecilomyces farinosus mass produced in shaken liquid cultures are infective per os and topically to Spodoptera exigua larvae. Pathogenicity of HB was greatest at pH 5.5. It was reduced by exposure for more than one-half hour to temperatures above 30°C. P. farinosus infected, killed, and produced mycelia on the surface of first-instar S. exigua larvae at a temperature—relative humidity combination as low at 15°C and 70% RH. Using two types of microdroplet applicators (droplet in the size range 1–30 and 30–90 μm, respectively) under field conditions, HB were delivered to distances of 76 m from the site of spraying. The number of HB deposited on the leaf surfaces of treated crops caused mortality of 70 to 90% in bioassayed larvae.

A mixed virus infection in midgut cells of Autographa californica and Trichoplusia ni larvae

Ultrastructural examination of the midguts of Autographa californica and Trichoplusia ni infected with a viral preparation obtained from Autographa nuclear polyhedrosis virus (AcMNPV)-infected insects revealed the presence of five morphologically distinct virus particles. Two virus particles were observed simultaneously in the nuclei, AcMNPV and an approximately 40-nm icosahedral unenveloped particle. Within the same cell two other viruses were observed in the cytoplasm, cytoplasmic polyhedrosis virus and a dense icosahedral unenveloped particle around 28 nm. A fifth particle resembling an icosahedral cytoplasmic deoxyribovirus was occasionally observed. Both the 40- and the 28-nm particles were observed to be occluded within polyhedra.

Electron microscope study on the replication of Autographa nuclear polyhedrosis virus and Spodoptera nuclear polyhedrosis virus in Spodoptera exigua

Abstract A comparative study of Spodoptera nuclear polyhedrosis virus (NPV) and Autographa NPV replication in Spodoptera exigua revealed some cytopathologic differences. Infection with Spodoptera NPV was accompanied by electron-dense intranuclear granules. Autographa infection within the midgut led to secretion within the lumens of the goblet cells of paracrystalline arrays of small, round particles, 9.5 nm in diameter. Autographa virus was also observed in various stages of possible replication within the cytoplasm.

Studies of transovum and transstadial transmission of a granulosis virus of the codling moth

Abstract Capsules of a granulosis virus of the codling moth were never found in codling moth eggs, although they were observed in the larval, pupal, and adult stages. However, eggs obtained from a British Columbia codling moth colony were found to have virus on the egg surface. Transstadial transmission of the virus from the larval to the pupal stage occasionally occurred after intact capsules had been inoculated per os into the larva. The virus was also occasionally transmitted from the pupal to the adult stage, but only after virions had been injected into the hemocoel of the pupa. Fertile eggs obtained from virus-injected insects were not shown to contain active virus. Eggs were tested by maceration in antiserum, by the fluorescent-antibody technique, and by bioassay of their contents. Only one larva of the F 1 and F 2 generations obtained from virus-injected insects succumbed to granulosis even when the larvae were exposed to various types of stressors. Circumstantial evidence supports the hypothesis of transovum transmission, but such transmission cannot be attributed to injections of virus into larvae and pupae in this study.

Electron microscope observations of the membrane surrounding polyhedral inclusion bodies of insects

SummaryParacrystalline inclusion bodies (polyhedra) which occlude insect viruses are bounded by two membrane units which are closely appressed. The membranes appear to be similar to those of cisternae found in the nucleus. These cisternae were observed associated with polyhedra in various stages of condensation and appression.

BIOLOGICAL FACTORS THAT AFFECT THE SUCCESS OF MICROBIAL INSECTICIDES: DEVELOPMENT OF INTEGRATED CONTROL

The integrated control concept has gradually gathered momentum during the past two decades as a practical and sensible way to deal with pest problems. Many successful programs have or are being developed for fruit, vegetable, and field crops; glasshouse-grown crops; and forest, shade, and ornamental plants and insects of medical importance (TABLE 1 ) . Interest in the integrated control approach has been stimulated mainly by the failures and disasters incurred by the almost total reliance on synthetic organic chemical pesticides to deal with pest problems. The heavy use of these chemical pesticides, without regard to the complexities of the ecosystem, especially the fundamental aspects of the population dynamics of pest species, has been the basic shortcoming of this approach. Several problems have resulted from the intensive and indiscriminate use of chemical pesticides: 1. There is the now well-documented phenomenon of insect resistance, with over 228 insect species in the world that have been reported to be resistant to chemical pesticides.I8 This problem has developed not only with the target species for which the pesticides were applied, but also for nontarget species in the vicinity. For example, the heavy use of pesticides for cotton pest control in Central America has produced selection of resistance and cross resistance by a malaria-transmitting mosquito, Anopheles albimanus, that inhabits many types of vegetation, including ~ o t t o n . ~ ~ , ~ ~ There is a resurgence or flareback of the target pest after application of a recommended pesticide. This results in the need for repeated applications of the pesticide to push the pest population back each time it returns. In California, larval populations of the cotton bollworm, Heliothis zea, frequently flareback after applications of the chemical insecticide dimethyl phosphate of 3-hydroxy-Nmethyl-cis-crotonamide ( rnonocrorophos) .40 3. The release of nontarget species occurs by the destruction of natural enemies that otherwise hold their populations in check. The released species can develop into secondary pests and thus also require control measures. In California, applications made for control of lygus bug, Lygus hesperus, on cotton, destroy insect predators, thus releasing the cabbage looper, Trichoplusia ni, and beet armyworm, Spodoptera exigua, to increase and cause damage.8.9r16s43 4. There is also environmental disruption that occurs outside the pesticidetreated area that may result in the increase of pest problems on adjacent crops or the creation of a pest problem where none existed before. This has occurred with a species of leafhopper, Dalbulus maidus, and corn stunt disease (mycoplasma) in the Pacific plain area of Central America. Prior to 1955, the vector 2 .

Electron microscope observations of Autographa californica (Noctuidae) nuclear polyhedrosis virus replication in the midgut of the saltmarsh caterpillar, Estigmene acrea (Arctiidae)

Abstract The nuclear polyhedrosis virus from Autographa californica was studied with the electron microscope in the midgut of the salt marsh caterpillar, Estigmene acrea . The results of the present study were compared with a previous study in which the same inoculum was fed to Spodoptera exigua . In Estigmene acrea polyhedra were produced, but virions were not occluded. Nonoccluded virions were found throughout the midgut cytoplasm and budding into the hemocoel. Within the cytoplasm, the rough endoplasmic reticulum was observed to contain paracrystalline proteinaceous bodies. Fibrous bodies and annulate lamellae were also found in the cytoplasm of infected cells.

Observations on the Interaction of Baculoviruses with the Plasma Membrane

Summary Two nuclear polyhedrosis baculoviruses were observed to acquire an envelope by budding through the plasma membrane. Budding (synhymenosis) occurred in a variety of tissues. The mechanism involved in the budding process appears similar to that described for other viruses and results in a characteristic surface structure similar to peplomers on one end of the virus.