Importance of timing,spore concentrations,and levels of spore carrier in applications of Nosema locustae (Microsporida: Nosematidae) for control of grasshoppers

In a study of microbial control of grasshoppers, Nosema locustae was applied to 10-acre plots in 2 replications of 24 treatment combinations in which the factors were (1) times of applications: 4 applications spaced over 22 days; (2) concentrations of spores: 1, 30, and 900 spores/in²; and (3) levels of the spore carrier: 1 and 4 lb wheat bran/acre. The concentrations of spores had the most effect in reducing the densities of grasshoppers and the incidence of infection among the survivors at the last sampling (coincided with the initiation of oviposition), the average reduction in density attributed to application of 1 spore/in² was 21%, that attributed to 30 spores/in² was 46%, and that attributed to 900 spores/in² was 73%. The first and second applications caused the greatest reductions in density; the second, third, and fourth applications produced the highest incidence of infections. Also, a higher incidence of infection was observed among grasshoppers from plots treated with 30 spores/in² on 1 lb bran/acre than from plots treated with 30 spores/in² on 4 lb of bran/acre. Therefore, a ratio of about 0.63–0.94 billion spores/lb bran applied at a rate of 1–1.5 lb/acre (= 100–150 spores/in²) at the time when the principal early summer species are third-instar nymphs would have resulted in overall reductions in density of 50–60%, with 35–50% of the survivors sufficiently infected so that fecundity would probably be affected. The reductions and incidence of infections would be higher in species that readily accept and use wheat bran, among which are some of the more economically important species of grasshoppers.     

Nosema invadens sp. n. (Microsporida: Nosematidae), a pathogen causing inflammatory response in Lepidoptera

States in the life cycle of Nosema invadens sp. n. are described from the raisin moth, Cadra figulilella, and the almond moth, Cadra cautella. In laboratory tests, larvae of the following Lepidoptera were also susceptible: Ephestia elutella, Plodia interpunctella, Galleria mellonella, and Paramyelois transitella. The midgut wall and Malpighian tubules were invaded first, but subsequently most other tissues were also infected. Severe inflammatory response accompanied infection, including hemocytic encapsulation of infected areas and hemocytic infiltration of fat tissue.     

The preservation of infective spores of Nosema necatrix (Protozoa: Microsporida) in Spodoptera exempta (Lepidoptera: Noctuidae) by lyophilization

Cadavers of Spodoptera exempta infected with Nosema necatrix were lyophilized. The lyophilized material was tested against a standard spore preparation 1 day after lyophilization and retested 2 yr later. There was some loss of spore viability. The feasibility of using dose-mortality experiments to estimate the loss in viability is discussed.     

Infection of the corn earworm, Heliothis zea, with Nosema acridophagus and Nosema cuneatum from grasshoppers: Relative virulence and production of spores

Per os inoculations of 4- to 6-day-old larvae of the corn earworm, Heliothis zea, with suspensions containing 10⁶ spores of Nosema acridophagus or 10⁴, 10⁵, and 10⁶ spores of Nosema cuneatum retarded the growth and development of the larvae. Migratory grasshoppers, Melanoplus sanguinipes, inoculated with N. acridophagus produced fewer spores than similarly inoculated corn earworms, but spore production was similar in these insects when they were inoculated with N. cuneatum. Standard bioassay procedures showed that spores of both microsporidians were some-what more virulent when they were produced in corn earworms than when they were produced in grasshoppers. Spores of these microsporidians might be produced more efficiently in corn earworm larvae than in grasshoppers.     

Reduction of consumption by grasshoppers (Orthoptera: Acrididae) infected with Nosema locustae canning (Microsporida: Nosematidae)

The effect of ingestion of Nosema locustae Canning spores on feeding by grasshoppers was measured in simultaneous laboratory and field experiments. After 21 days, fourth-instar Melanoplus sanguinipes (F.) nymphs, administered spores at the rates of 0, 2.0 × 10⁴, 2.0 × 10⁵, and 2.0 × 10⁶ per grasshopper, showed dry matter consumption of 102, 87, 64, and 26 mg in 48 hr, respectively. Rate of inoculation was a significant factor in suppression of feeding after correction for the effects of developmental stage, sex, and body weight. The quantity of dry matter consumed decreased linearly with increasing rate of spore ingestion. Experiments on 50 caged 1-m² plots on pasture grass yielded similar trends in per capita consumption independent of the effects of mortality. Field consumption per integrated grasshopper-day was 108, 77, 31, and 27 mg dry wt at the four inoculation rates, over 20 days.     

Some factors affecting spore replication of Nosema algerae (Microspora,Nosematidae) in Pieris brassicae (Lepidoptera)

The production of Nosema algerae spores was examined in Pieris brassicae. Spore replication in the insect host followed a logistic pattern of development. The factors studied which affected spore production and replication were dose level (5 × 10², 5 × 10³, and 5 × 10⁴ spores per insect), larval instar (fourth and fifth), and cool pretreatment of the insects at 20°C prior to inoculation compared with a constant temperature of 26°C. A three-way analysis showed the interactions between these factors. The logistic pattern of spore replication was used to explain the results.     

Transmission and infectivity of spores of Burenella dimorpha (Microsporida: Burenellidae)

Burenella dimorpha infects the tropical fire ant, Solenopsis geminata, producing two morphologically distinct types of spores. A binucleate, nonpansporoblast membrane-bounded (NPMB) spore develops in and destroys the hypodermis, rupturing the cuticle in the pupal stage. A uninucleate, pansporoblast membrane-bounded (PMB) spore develops in the fat body. Adult ants cannibalize ruptured pupae but do not ingest spores. Instead, the spores and particulate foods are diverted to the infrabuccal cavity, formed into an infrabuccal pellet, and fed to fourth-instar larvae only. This larval instar is the only stage in the life cycle of S. geminata that is vulnerable to infection. NPMB spores are infective, but PMB spores do not extrude their polar filaments in the larval gut and are expelled in the meconium upon pupation.     

A redescription of Nosema herpobdellae (Microspora: Nosematidae), a parasite of the leech Erpobdella octoculata (Hirudinea: Erpobdellidae)

Nosema herpobdellae was recorded in populations of the leech Erpobdella octoculata from lakes in northwest England and North Wales and is redescribed using light and transmission electron microscopy. It differes from N. glossiphoniae in the nature of the infection and tissues parasitized and from N. tractabile in its larger spore size, longer polar filament, in the angle of the anterior coils of the polar filament to the spore long axis, and apparently in its developmental cycle. The infection was found in a massive xenoma, in the connective tissue surrounding the gut, which was presumed to be formed from a single hypertrophied cell. Its developmental cycle included merogony and sporogony.     

蝗虫微孢子虫的生产及田间应用现状

蝗虫微孢子虫是国际上商品化的微孢子虫杀虫剂,在对蝗虫的生物防治方面具有重要作用。介绍了关于蝗虫微孢子虫的基础理论知识、大规模生产技术及田间应用现状,同时对利用蝗虫微孢子虫进行害虫生物防治提出了一些有益的建议。     

The effect of ultraviolet radiation on the germination of Nosema algerae Vávra and Undeen (Microsporida: Nosematidae) spores

Spores of Nosema algerae Vávra and Undeen were subjected to various dosages of 254 nm ultraviolet radiation (UV). Very high dosages of UV were required to block germination. Germination was normal immediately after UV dosages of 0.2 to 1.0 J/cm2, followed by a delayed effect in which both percentage germination and the intrasporal concentration of trehalose decreased with time after UV exposure. Although a few spores were germinated, most of them were inactivated (rendered temporarily unable to germinate) by exposure to UV of 1.1 J/cm2. Ultraviolet radiation between 1.1 and 3.4 J/cm2 stimulated spores to germinate. However, spores were completely unable to germinate immediately after exposure to dosages above 3.8 J/cm2. Ammonia had little effect on stimulation by UV but was inhibitory to germination after stimulation had occurred. These results demonstrate that UV behaves like a germination stimulus and are discussed in terms of the hypothesis that germination is initiated by the breakdown of barriers between trehalose and trehalase.     

Persistence of spores of Pleistophora schubergi (Cnidospora: Microsporida) in the field,and their application in microbial control

Spores of Pleistophora schubergi, when applied to oak trees in the field at 2 × 10⁸ spores/ml with a uv protectant, “Shade,” infected 88% of Anisota senatoria larvae at 4 days after spray application. Spores without the uv protectant infected only 10% of the larvae at 4 days after application. When the spores were applied at the rate of 2 × 10⁸ and 2 × 10⁷ spores/ml in the field, 96 and 72% of the A. senatoria larvae and 100 and 100% of the Symmerista canicosta larvae were infected 14 days after spray application.     

Light and electron microscope observations on Unikaryon legeri (Microsporida,Nosematidae), a parasite of the metacercaria of Meigymnophallus minutus in Cardium edule

Nosema legeri from the metacercariae of Meigymnophallus minutus in Cardium edule has been shown by light and electron microscopy to be disporous and to lack nuclei in diplokaryon form throughout its development. Although its ultrastructure resembles that of Encephalitozoon cuniculi and mature spores often lay in vacuoles surrounded by host membranes, dividing stages were never present in a common vacuole. Sporoblasts showed a cytoplasmic protuberance suggestive of a locomotory organelle. It is possible that movement of these stages disrupts the host cell cytoplasm and creates the vacuole in which the spores mature. The species has been transferred to the genus Unikaryon Canning, Lai and Lie and named Unikaryon legeri(Dollfus, 1912).     

Presence of Nosema ceranae in honeybees (Apis mellifera) in Uruguay

The microsporidium Nosema ceranae is an emergent pathogen of European honeybees Apis mellifera. Using a PCR-RFLP diagnosis, 29 samples of infected honeybees obtained in 2007-2008 (N = 26), 2004 (N = 2) and before 1990 (N = 1) were analyzed for the presence of Nosema apis and N. ceranae. Only N. ceranae was found in all samples, indicating that this species dispersed to Uruguay (and likely the region) at some time before 1990. The presence of N. ceranae in Uruguay is not associated with an increase of Nosemosis, and its role in colony loss seems to be irrelevant.     

The Ultrastructure of Encephalitozoon cuniculi (Microsporida,Nosematidae) and its Taxonomic Significance*

SYNOPSIS. This study augments our knowledge of several ultrastructural features of Encephalitozoon cuniculi and provides evidence that this species is disporous. We support Cali's view that Encephalitozoon is distinct from Nosema and should be treated as a valid genus. We compare these with 2 other disporous genera, Glugea and Perezia, and conclude that Glugea is also distinct but Perezia is a junior synonym of Nosema.