A method for identifying individual second-stage juveniles (J2s) of three major Meloidogyne spp. in Japan was developed. Spores of three isolates of Pasteuria penetrans from Meloidogyne incognita (Mi), M. arenaria (Ma) and M. hapla (Mh) were sonicated to increase the number of spores attaching to J2s of Meloidogyne spp., they were then stained blue with Brilliant Blue G, orange with Acridine Orange, and violet with Methyl Violet, respectively. When J2s of Mi, Ma and Mh were mixed with these stained spores, each J2 was identified individually according to the color of the most abundantly attached spores on the body surface. In the case of mixed nematode suspensions containing Meloidogyne spp., free-living nematodes and Pratylenchus sp., the stained spores attached only to J2s of Meloidogyne spp., and the species of each J2 was discriminated by the spore color. This method is also applicable foridentifying individual J2s of most populations of Mi, Ma and Mh from Japan, and is useful for estimating the numbers of J2s of each Meloidogyne spp. in mixed-nematode samples.

View full abstract

Seven Pratylenchus species including P. brachyurus, P. coffeae, P. crenatus, P. neglectus, P. penetrans, P. zeae, and a Pratylenchus sp. which is morphologically indistinguishable from P. coffeae, were compared on the basis of the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis using a single nematode. The PCR primers used amplified the two internal transcribed spacer (ITS) regions, i. e. the 5.8S gene, and small portions of the 18S and 28S genes of the ribosomal DNA (rDNA). The isolates of P. penetrans, P. coffeae and Pratylenchus sp. yielded a single fragment after PCR amplification. Each frag-ment size was about 0.75 kb in P. penetrans, and about 1.1 kb in P. coffeae and Pratylenchus sp. The other nematodes, newly examined in this study, P. brachyurus, P. crenatus, P. neglectus and P. zeae, gave two PCR amplification products. The sizes of the two fragments were about 0.7 kb and 0.75 kb in P. brachyurus, P. neglectus and P. zeae, and about 0.8 kb and 0.9 kb in P. crenatus, respectively. These seven species were easily discriminated according to species-specific patterns by digesting the amplified products with endonucleases, AluI, HhaI, HinfI and TaqI.

View full abstract

Cotesia plutellae is a major solitary larval endoparasitoid of the diamondback moth, Plutella xylostella which is a cruciferous pest. We investigated the subsequent sex ratio of progeny, growth and development of C. plutellae when parasitization occurred at the 2nd, 3rd, and 4th host stadia. Furthermore, cues by which males enhance the opportunities to encounter potential mates were examined. Although successful parasitism of 4th instars showed a lower percentage of parasitism than those of the other stadia, no difference in sex ratio of progeny was observed at any host stadium. The ratio of females among the progeny and the parasitism rate decreased with the age of the females. The developmental duration of male wasps tended to be shorter than that of females at all stadia for which parasitization occurred, indicating protandry. The presence of host plants, i.e., a cabbage leaf, reduced the time necessary for males to successfully locate mates. Damage to cabbage due to the diamondback moth caused an increase in the number of males flying around and landing on leaves near the females, suggesting that males searching for females over a long range needed both stimulants produced by the host larvae and a female pheromone.

View full abstract

The development and reproduction of Orius sauteri reared on Thrips palmi larvae were studied at four constant temperatures, 15, 20, 25 and 30°C. Thermal constant (K) and developmental zero (T₀) for eggs and nymphs of O. sauteri were calculated at 62.1 day-degrees and 11.1°C and 180.8 day-degrees and 10.3°C, respectively. Egg mortality rate was always 7.1% or less. There was no significant difference in survival rate during the nymphal stage among the four temperatures. Longevity of female and male adults was greatest at 15°C and shortest at 30°C. Female lifetime fecundity reached a maximum at 25°C. The intrinsic rate of natural increase (γ_m) was highest at 30°C.

View full abstract

Adults of the West Indian sweet potato weevil, Euscepes postfasciatus were effectively marked with Calco Oil Red N-1700^〔○!R〕 dye contained in the larval artificial diet. Addition of the dye to the diet had no significant effects on developmental period from egg hatch to adult eclosion, yield of adults, or the percent hatchability of eggs oviposited by marked adults. The color of the dye in the adult metathorax was still visible externally even 6 weeks after eclosion. These results indicate that the dye is useful as an internal marker of E. postfasciatus in the sterile insect technique.

View full abstract

Repeated attempts to directly compare the activity of the two reported phenotypes (plasma-enveloped, budded virus and polyhedral-derived virus) have been thwarted by the presence of proteinaecous occlusion bodies. The availability of deleted polyhedrin-gene strains of baculoviruses now makes this comparison possible without the use of inactivating, occlusion-body dissolving reagents. Exocellular virus (EXCV), harvested from the supernatant, or intracellular virus (INCV), harvested from intact cells of 24-h and 96-h cultures were used. Both a wild strain (WtAcMNPV) and a deleted polyhedrin-gene strain (PAcMNPV) were used to compare the in vivo activity of the two phenotypes of the nucleopolyhedrovirus of Autographa californica (AcMNPV). The following results were obtained when the EXCV and INCV were administered (per os and by intrahemocoelic injection) to cabbage looper larvae, Trichoplusia ni. When fed to T. ni larvae : (1) EXCV harvested from a 96-h culture of WtAcMNPV was ca. 17-fold more active than EXCV harvested after 24-h of culture ; (2) after 24-h of culture INCV was ca. 167-fold more active than EXCV ; and (3) after 96-h of culture INCV was ca. 29-fold more active than EXCV. There was no difference in activity between EXCV and INCV when T. ni larvae were intrahemocoelically injected.

View full abstract

Interactions between the Hawaiian strain of a granulovirus of Pseudaletia unipuncta (PuGVH) and a gregarious braconid endoparasitoid, Cotesia kariyai, in Pseudaletia separata larvae were examined. The results showed that infection of larvae with PuGVH was deleterious to the development and survival of C. kariyai. No parasitoid larvae emerged from PuGVH-infected hosts when the second and third instars were infected with PuGVH and then parasitized at the fourth stadium. Further, no parasitoid larvae also emerged from PuGVH-infected hosts when the fourth instars of P. separata were simultaneously parasitized and infected with PuGVH. Virion-free plasma from PuGVH-infected P. separata larvae was toxic to the parasitoid larvae even up to a dilution level of 256 when it was injected intrahemocoelically into parasitized host larvae. Toxicity of the virion-free plasma was maintained for at least 4 d after its injection into host larvae. Addition of the virion-free plasma was also toxic to the in vitro-cultured parasitoid larvae, even up to a dilution level of 625. The cuticles of dead parasitoid larvae were separated from the somatic tissues.

View full abstract

The abundance of insect pests is expressed as the density per plant in most cases. This measure, however, is not always an appropriate measure of density, since the size of a plant varies greatly with its growth stage. To evaluate the importance of selecting an appropriate measure of density, the dynamics of the density of cabbage pests per leaf area was compared with that per plant. The leaf area was continuously estimated in the field in a noninvasive manner, using the allometric relationship between leaf area and leaf length. Density per leaf area and density per plant showed widely different dynamics in some herbivores. Aphid density per plant increased gradually with the growth of cabbages, while aphid density per leaf area decreased with cabbage growth, suggesting that injury by aphids was more severe in the early stages of plant growth. The larval density of the diamondback moth, Plutella xylostella (Linnaeus), per plant increased with cabbage growth, while the density per leaf area showed a peak level at 15 days after transplanting. Such differences suggest that population dynamics measured per plant may sometimes be a misleading description of actual insect-plant interactions.

View full abstract

Four continuous cell lines were established from cultures of embryonic tissue of the silkworm, Bombyx mori, and designated NISES-BoMo-MK, NISES-BoMo-KG, NISES-BoMo-DZ, and NISES-BoMo-OH. The cells were mostly spherical in shape, and could be cultured at 25°C to 37°C. The population doubling time of each cell line was not affected by the temperatures employed, being about one day at both 25°C and 37°C. The karyotype of the cells was typical of lepidopteran cell lines. The number of chromosomes was higher at 37°C than at 25°C. The activity of the enzymes, phosphoglucose isomerase, phosphoglucomutase, isocitrate dehydrogenase, and glucose-6-phosphate dehydrogenase extracted from the cells was higher at 37°C than at 25°C. None of these novel cell lines formed any polyhedra, even with high titer inoculation of Bombyx mori nuclear polyhedrosis virus.

View full abstract

Diapause and non-diapause larvae of Plodia interpunctella from two selected lines, fast development (FDL) and slow development (SDL), reared at 20°C and 25°C were tested for low temperature tolerance, supercooling ability and accumulation of cryoprotective compounds. Exposure to -20°C was fatal for both diapause and non-diapause larvae. Diapause larvae, particularly those reared at 20°C, were more tolerant to -10°C than non-diapause larvae. Their higher survival under increased exposure periods indicates that the chilling tolerance in P. interpunctella is associated with diapause. Rearing temperatures did not affect the supercooling capacity of the larvae, since the supercooling points (SCPs) of the diapause and non-diapause larvae reared at 20°C and 25°C did not differ ; mean SCPs ranged from -12°C to -15°C. Trehalose was the major cryoprotective compound synthesized by the larvae. Photoperiod and temperature affected the accumulation of trehalose as diapause larvae reared at 20°C (LD 12 : 12) had significantly higher concentrations of trehalose than non-diapause larvae at 20°C and diapause and non-diapause larvae at 25°C. Low temperature (5°C) exposure for 30 days enhanced the supercooling ability of diapause larvae reared at 20°C by decreasing the SCP to ca. -22°C. The results suggest that diapause larvae can overwinter successfully in a supercooled state. Acclimation did not increase trehalose concentration. This leads to the conclusion that the regulation of supercooling in P. interpunctella is independent of trehalose concentration. Diapause and non-diapause larvae from the two selection lines did not differ in SCP, concentration of cryoprotectants, or rate of survival at low temperature.

View full abstract