Minoru Tamashiro

Pathogenicity of six strains of entomogenous fungi to Coptotermes formosanus

One strain (2A3) of Beauveria bassiana, two strains (N-22; T-27) of Beauveria sp., and three strains (Tonga; 10B; MM-773) of Metarhizium anisopliae were tested for their pathogenicity to workers from a colony of Coptotermes formosanus. A microsyringe method for estimating and applying the inoculum was employed in these tests. On the basis of LD50 and fiducial limits, the pathogenicity, in descending order, was MM-773 > 10B = N-22 = 2A3 = T-27. Because of heterogeneity, the fiducial limits of the Tonga strain overlapped all of the other isolates except for MM-773. Except for the Tonga strain, M. anisopliae appeared to be more pathogenic than Beauveria. LD95 and LT50 of these fungi were also determined.

The biology and pathogenicity of a microsporidian (Nosema trichoplusiae sp. n.) of the cabbage looper, Trichoplusia ni (Hubner) (Lepidoptera: Noctuidae)☆

Abstract Biological studies of a microsporidian pathogenic for the cabbage looper, Trichoplusia ni (Hubner), were conducted and its effect on the host was determined. Comparisons of certain characteristics of this Microsporidia with those of other Nosema revealed apparent differences, indicating an undescribed species. The name Nosema trichoplusiae sp. n. has been proposed for it. The life cycle of N. trichoplusiae was studied in Giemsa-stained smears of infected larvae, and the developmental stages were arranged on the basis of the present knowledge of cell division and nuclear changes. The effect on N. trichoplusiae on the reproductive capacity of T. ni varied with the intensity of infection in the larval stage. Adults from heavily infected cabbage loopers laid only one-fourth to one-sixth as many eggs as uninfected adults and the viability of these eggs was very low. On the other hand, lightly infected females produced a number of eggs comparable both in number and viability to that of the uninfected adults. However, the few larvae that did hatch from the eggs laid by any of the infected females were infected and died before completing the larval cycle. Thirteen lepidopteran species in five families were found to be susceptible to infection by N. trichoplusiae. However, none of the Diptera which were used as candidate species were affected by the microsporidian.

Interactions between a microsporidian pathogen of the lawn-armyworm and the hymenopterous parasite Apanteles marginiventris

The hymenopterous parasite Apanteles marginiventris oviposited with equal frequency in Nosema-infected and in uninfected lawn-armyworm (Spodoptera mauritia acronyctoides) when the hosts were exposed in separate containers. When the hosts were exposed together, however, the parasites seemed to prefer the infected hosts although the difference was not statistically significant. Nosema-infected hosts had deleterious effects on their internal parasites. There was high parasite larval and pupal mortality, greatly reduced adult emergence, and those few adults that did emerge were smaller and significantly shorter-lived than the parasites from uninfected hosts. These detrimental effects did not derive from a direct infection of the parasite by Nosema, but rather, because an infected host apparently was not completely adequate for parasite development. There were no observable pathological changes in the tissues of parasites reared in infected hosts. The parasites successfully transmitted the pathogen from severely infected hosts to noninfected hosts during oviposition.

Changes observed in hemolymph proteins of the lawn armyworm, Spodoptera mauritia acronyctoides, during growth, development, and exposures to a nuclear polyhedrosis virus☆

Abstract Vertical electrophoresis with acrylamide gel was used to study the effects of a nuclear polyhedrosis virus (NPV) on the hemolymph proteins of Spodoptera mauritia acronyctoides . An electrophoretic pattern consisting of 20 basic bands of proteins was separated in hemolymph of normal larvae which were older than 17 days. These hemolymph proteins increased quantitatively during growth. All 20 proteins could not be detected in hemolymph of younger larvae by the techniques utilized. Additional proteins were separated with metamorphosis. Lethal doses of NPV resulted in a general reduction of hemolymph proteins (hypoproteinemia) in infected larvae. Sublethal doses of NPV elicited an increase in certain hemolymph proteins. Similar increases in proteins were also observed in larvae surviving ostensibly lethal levels of NPV, in larvae subjected to physical stress, and in larvae reared axenically without formaldehyde in their diets. These same proteins, however, were present in approximately the same quantities in mature larvae. Physiopathology of NPV in S. mauritia appears to involve stress factors, host reactions, and the host endocrine system.