Pathogens of Ips amitinus: new species and comparison with Ips typographus

Ips amitinus and I. typographus are two serious pests of spruce in Europe, have similar bionomics and are likely to occur and meet on the same host trees. We therefore hypothesized that the two species support similar levels of similar pathogens. To test this hypothesis, we collected mature beetles from three trap trees at each of eight study sites and determined beetle numbers and pathogen infection levels. In total, 938 mature I. amitinus beetles and 3435 of I. typographus were dissected; five pathogens, as well as intestinal nematodes and endoparasitoids, were detected. The neogregarine Mattesia schwenkei is reported here for the first time as a new pathogen in 9.4% of I. amitinus individuals at one site. Average infection levels of most pathogens (Chytridiopsis typographi, Gregarina typographi, Mattesia schwenkei and parasitoids) were significantly higher in I. typographus than in I. amitinus. Metschnikowia typographi was confirmed only in Ips amitinus, while the microsporidium of Nosema typographi occurred only in I. typographus. Within‐season increases in G. typographi infection levels were documented in Ips amitinus.     

Studies on the Life History of a Neogregarine Parasite Found in Leptothorax Ants from North America

Pupal stages of Leptothorax ants collected near West Yellowstone, MT, USA, displayed striking signs and symptoms of disease, i.e., grey to black coloration, irregular pigmentation of compound eyes and toothless mandibles. Light microscope studies revealed heavy infections by a neogregarine, the life history of which is described. The life cycle of the pathogen includes micronuclear and macronuclear schizogonies, gametogony and sporogony. Schizonts of both types vary in size depending on the number of nuclei which is usually defined by doubling, thus giving rise to 8, 16, 32, 64 or even 128 uninucleate merozoites. In smears and sections, micronuclear merozoites are typically arranged in rosettes. In the early transformation of zygotes, sickle-shaped developmental stages have been encountered, so far undescribed from neogregarines. Two spores (oocysts), each developing eight sporozoites, evolve from each gametocyst, as is typical of the genus Mattesia. Mature lemon-shaped spores measure 13.8 9.3 μm in fresh preparations. Infections can be readily transmitted to healthy colonies and to other Leptothorax species by feeding crushed infected pupae. Vegetative life cycle stages grow and multiply in the haemocoel, only to some extent they infect fat body cells. Macronuclear merozoites invade the hypodermis and the fat body but also settle extracellularly in the haemocoel. The disease process terminates with the death of the pupae that harbour abundant spores. Infections of adults have not been observed. Despite some minor differences that may result from development of the pathogen in this host, from the type, sequence and morphology of life cycle stages and from the signs and symptoms of disease, this Mattesia species is identified with M. geminata, first discovered in the tropical fire ant, Solenopsis geminata (Fabricius).     

The effect of sublethal neogregarine infections in the spruce needleminer, Epinotia tedella (Lepidoptera: Tortricidae)

Abstract.

• 1 A hitherto unknown factor causing cyclic reduction in population fertility of Epirzotia tedella (Cl.) was identified as sublethal infections of the neogregarine Mattesia sp.
• 2 Infection probably takes place when larvae enter hibernation, but does not develop into spore production until the formation of pupae and adult moths.
• 3 At the individual level, the sublethal neogregarine infection causes a slight delay in adult emergence, a decreased adult lifespan, a suppression of egg development, and thus a reduction in fertility.
• 4 At the population level, fertility reduction has a delayed density dependent component and, through correlation, Mattesia is assumed to be causative. Since fertility reduction is a key-factor in E.tedella, Mattesia may even be a dominant factor in the dynamics of this species.
• 5 Mattesia infections were found in no other dominant insect species at the locations, and consequently the interaction between E.tedella and Mattesia sp. seems to be specific. Such delayed density dependent interaction can create host oscillations, as seen in many forest insects. However, host-parasitoid interaction alone leads to oscillations with the observed period of 6–8 years length, and the neogregarine infections apparently act in parallel with the parasitoids and enhance the amplitude of the oscillations.

     

Pathogens of the bark beetle Ips cembrae: microsporidia and gregarines also known from other Ips species

The objective of the current study was to identify pathogens of the large larch bark beetle, Ips cembrae, which is a secondary pest that has produced several local outbreaks across Europe in recent years. Beetles were collected from pheromone traps, trap trees and emergence traps (Larix decidua) during 2007 to 2011 at 10 study sites in central Europe. A total of 3379 mature and callow beetles were examined with a light microscope, and only two microsporidian pathogens [Chytridiopsis typographi and a diplokaryotic microsporidium (probably Nosema sp.)] and two gregarines (Gregarina typographi and Mattesia schwenkei) were found. Within the I. cembrae populations, the infection rate for C. typographi ranged from 2 to 58%. Nosema sp. occurred in only two beetles in 2007 (at two study sites). G. typographi was recorded only in Austria and Croatia and only in 1–2% of the beetles in those countries. Mattesia schwenkei was observed solely in Croatia in 0.6% of the beetles in that country. Only one fungal pathogen in the genus Fusarium was found and only in two mature beetles (0.7%) in 2010. The pathogen species found during our study of I. cembrae were very similar to the pathogens previously identified for Ips typographus. No species‐specific pathogen was detected.     

Mattesia oryzaephili (Neogregarinorida: Lipotrophidae), a Pathogen of Stored-Grain Insects: Virulence, Host Range and Comparison with Mattesia dispora

The neogregarine, Mattesia oryzaephili (Neogregarinorida: Lipotrophidae) has only been reported from the sawtoothed grain beetle, Oryzaephilus surinamensis. The pathogen's presence in cadavers of the rusty grain beetle, Cryptolestes ferrugineus, in collapsed colonies prompted studies of its potential to control stored-product insects. Respective mortality rates in fourth instar C. ferrugineus and C. pusillus were 15.3 and 17.7% at 10² oocysts/g of diet and 89.4 and 80.5% at 10⁵ oocysts/g. The mortality of fourth instar O. surinamensis exposed to 10⁵ oocysts/g was only 12%. For C. ferrugineus larvae, there were no significant differences in mortality and infection between exposure to Mattesia dispora and exposure to M. oryzaephili (P>0.05), but for C. pusillus larvae, both responses were significantly higher for M. oryzaephili than M. dispora. Adult C. ferrugineus and O. surinamensis were similar in their responses to M. oryzaephili, with mortality not exceeding 20%, but differed in their responses to M. dispora, with O. surinamensis being more susceptible. The median lethal doses for larval Mediterranean flour moths, Ephestia kuehniella, were 7.9×10⁷M. oryzaephili oocysts/g of diet and 2.7×10³M. dispora oocysts/g of diet. In single dose assays of M. oryzaephili physiological host range, greater than 75% infection was achieved for Rhyzopertha dominica and Plodia interpunctella. More than half of oocysts germinated during passage through the guts of susceptible and resistant insects. Second and third instar Galleria mellonella were highly susceptible to M. oryzaephili infection, but fifth instars were not. Infection percentages in fifth instars exposed to 10⁶ oocysts/g were significant only when boric acid or the stilbene, Blankophor®RHK were incorporated into the diet. Host range and general morphology confirm the identity of Mattesia oryzaephili.     

Ultrastructural study of developmental stages of Mattesia dispora (Neogregarinorida: Lipotrophidae), a parasite of the flour moth Ephestia kuehniella (Lepidoptera)

The ultrastructure of merozoites, gamonts and oocysts of the neogregarine Mattesia dispora and their development in larvae of the flour moth Ephestia kuehniella were studied by electron microscopy. The apical complex of free macronuclear merozoites was very distinct in micrographs of sections, the polar rings being especially prominent. Two gamonts associated in head-to-head syzygy and the apical complexes served as the contact point during pairing. At this stage the rhoptries became reduced and the conoid widened. The gamonts had a foam-like appearance in the light microscope. Paired gamonts formed an envelope and developed into a gametocyst, within which the gamonts were separated by a distinct border. Four gametes and two residual cells developed inside the gametocyst. The gametes were covered with a single membrane. The gametes fused in pairs to form two spherical zygotes, each covered by two membranes and with one large nucleus. The external layer appeared more undulated than the inner one. A single membrane covered each residual cell. Walls were formed around both zygotes to produce two oocysts. Each mature oocyst was lemon-shaped with polar plugs and eight peripheral sporozoites, which had a pellicle similar to that of the merozoites, lay beneath the thick oocyst wall.     

Detection of Mattesia oryzaephili (Neogregarinorida: Lipotrophidae) in grain beetle laboratory colonies with an enzyme-linked immunosorbent assay

An indirect sandwich enzyme-linked immunosorbent assay (ELISA) for the detection of the neogregarine Mattesia oryzaephili was developed with monoclonal antibodies. It was used to screen laboratory colonies of Oryzaephilus surinamensis, Cryptolestes ferrugineus, C. pusillus, and C. turcicus from the United States, Canada, and Australia. All of the colonies except C. turcicus had larvae that tested positive with the percent of positives ranging from 0.2 to 83.9, but only colonies that tested positive had reported population declines. This assay will make possible epizootiological studies to assess the impact of M. oryzaephili on pest populations.     

Mattesia geminata sp. n. (Neogregarinida: Ophrocystidae) a Parasite of the Tropical Fire Ant,Solenopsis geminata (Fabricius)*

SYNOPSIS. A new species of neogregarine, Mattesia geminata sp. n., that infects immature stages of the tropical fire ant, Solenopsis geminata (Fabricius), is described. The parasite, which develops in the hypodermis, causes disruption of the developing eyes, melanization of the cuticle, and death of pupae. lntracolonial infection rates are usually less than 2±, but may exceed 90±. Attempts to transmit the infection were unsuccessful.