We studied the effects of temperature on the growth and sporulation of six isolates of Pyrenophora teres Drechsler, which causes net bloch of barley. Temperatures for growth in culture ranged between 5 and 30°C; the optimum was 25°C. Sporulation in culture was abundant at 20-25°C, moderate at 15°C, and absent at 30°C over 10 days; and moderate at 10°C over 21 days. Net blotch appeared in fields of barley (cv. Asakagold) in 2000, 2001, and 2002 in Fukuoka prefecture. During the winter in early 2000 at normal cold temperatures, seedlings became infected through seed, but the infection did not develop systemically. During the warm winters in early 2001 and in early 2002, net blotch spread. These results suggest that a warm, wet winter promotes the spread of net blotch.

View full abstract

We investigated the effect of aluminum-coated tape and white netting on Potato virus Y(PVY) infection in potatoes in the field. We stretched tapes ( 5 cm wide) at 135 cm above the ground along the ridges and across the furrows in an X shape (taped plots), or placed white nets (1-mm mesh) 135 cm above the ground (netted plots), or did both. In the taped plots, the number of winged aphids trapped was 20% to 48% of the number trapped in untreated plots during the growing season. In the taped and netted plots, the number was 9% to 33% of the control. Tapes plus insecticides and tapes plus netting plus insecticides both reduced PVY incidence in leaves to as little as 17% compared with insecticides alone. Average percentages of PVY-infected potato tubers were reduced to 33% by tapes plus insecticides, and to 50% by tapes plus netting plus insecticides. Our results suggest that tape along with white netting can reduce PVY incidence in leaves and tubers in the field. Reducing the quantity of tape to one or two thirds to reduce labor and cost and stretching tapes did not affect PVY incidence. White netting alone did not reduce alate aphid landing or PVY incidence.

View full abstract

Strawberry anthracnose, caused by Glomerella cingulata, developed in symptomless mother plants and daughter plants. Transmission from symptomless infected plants continued from April to July when of mother plants beds were dug up. Transmission increased with temperature beyond 20°Cand much rain.

View full abstract

Systematic application of fungicides to strawberry mother plants and daughter plants under a rain shelter gave effective control of strawberry anthracnose in symptomless mother plants infected with Glomerella cingulata. Fungicide alone and rain shelter alone gave less effective control than the combination.

View full abstract

[in Japanese]

View full abstract

We investigated Satsuma mandarin 'Haraguchi Wase' trees on trifoliate orange rootstocks showing exocortis-like symptoms. The results of bioassay using 'Etrog' citron (Arizona) 861-S1 and RT-PCR showed that the trees were infected with 1 to 4 citrus viroids but not with citrus exocortis viroid (CEVd). According to a survey, the more serious was the damage to the rootstock, the larger was the decrease in tree canopy volume and trunk diameter. It appeared that multiple infection caused enormous damage, such as bark scaling, which is normally characteristic of CEVd infection in trifoliate orange rootstock. We suspect that hop stunt viroid (HSVd) and citrus viroid-III (CVd-III) in the viroid complex causes severe symptoms in trifoliate orange rootstock, and that additional infection with CVd-OS and/or CVd-I-LSS causes even worse damage.

View full abstract

[in Japanese]

View full abstract

Cicadulina bipunctata (Melichar) (Homoptera: Cicadellidae) induces maize wallaby ear disease. Following the initiation of biyearly plantings of forage maize in Kumamoto, Japan, in 1988, C. bipunctata became a pest of the second planting. Recently, the area of forage maize fields damaged by C. bipunctata has expanded in Kikuchi, Kumamoto. To clarify the current damaged area and the field life cycle of C. bipunctata, we surveyed distribution, abundance, and seasonal occurrence of C. bipunctata in forage maize fields and surrounding areas in Kikuchi, in 2004. C. bipunctata inhabited most of the cultivated area of forage maize in Kikuchi, and the density was high enough to cause severe damage at many sites. In neighboring fields, C. bipunctata occurred mainly from July to December, with a peak of occurrence in October. A possible factor affecting the recent expansion of damaged area and outbreaks of C. bipunctata is the relatively low winter mortality of C. bipunctata due to the high average temperature in recent years, attributable to global warming.

View full abstract

We tested the suppression of bacterial contamination of artificial diet by 5-min submersion of Euscepes postfasciatus eggs in 70% ethanol before a simple egg-seeding method that is used for mass-rearing of other weevil species. In this egg-seeding method, eggs are suspended evenly in a sterile furcellaran solution (a viscous liquid): the mixture is then dropped onto the surface of the diet. When weevil eggs rinsed only with sterile water were mixed with the solution and placed on the diet, bacterial colonies formed in all replicates within 3 days. Ethanol treatment of the eggs before mixing with the solution significantly reduced and delayed formation of bacterial colonies on the surface of the diet by 29% and 8d, respectively. However, these values were significantly less than those achieved by an ordinary egg sterilization method (20-min submersion in 5% formaldehyde; 71% and 13d). Therefore, it appears that ethanol treatment of E. postfasciatus eggs alone is insufficient for preventing bacterial contamination of diet in the mass-rearing of E. postfasciatus.

View full abstract

To implove the mass-rearing of the West Indian sweetpotato weevil, Euscepes postfasciatus. on artificial diet, we tested whether either of two environmental factors affected egg hatching of this species. The first factor was the light/dark condition during egg incubation. The second was submersion of eggs in furcellaran solution, a viscous liquid that is used to scatter eggs evenly on the diet surface in mass-rearing of other weevil species. E. postfasciatus eggs were divided into two groups: those kept in a clear Petri dish and those kept in a light-tight Petri dish. Both were incubated for six days at 25±1°C in 14-h light: 10-h dark. After incubation, eggs from each dish were divided into two subgroups: one was submerged in 0.6% furcellaran solution and the other was not. There was no significant difference among the four treatments in hatchability. mean egg period (days from oviposition to hatching), or coefficients of variation of egg period. We conclude that neither of the light/dark condition nor submersion in the furcellaran solution has any effects on egg hatch of E. postfasciatus. These results suggest that the furcellaran solution can be used as an egg-seeding agent in the mass-rearing of E. postfasciatus.

View full abstract

We compared survivorship and development of larvae of the common cutworm, Spodoptera litura, on soybean cultivar 'Bay' with those on cultivars 'Fukuyutaka' (susceptible) and 'Himeshirazu' (resistant) under greenhouse conditions. Larvae reared on Bay had significantly longer larval duration and developed into lighter pupae than those reared on Fukuyutaka when they were released at the 2nd instar. The 6th (final) instar larvae on Bay showed similar body weight changes to those of the larvae on Himeshirazu, resulting in higher mortality, longer larval duration, and lighter pupae than on Fukuyutaka. These results reveal that Bay has a high level of antibiosis and is resistant to S. litura. Early survival rates and the pattern of weight change of 2nd instar larvae differed greatly between Bay and Himeshirazu. Thus, the mechanism of resistance to S. litura seems to differ between Bay and Himeshirazu.

View full abstract

[in Japanese]

View full abstract

We examined efficiencies of transmission of Tomato spotted wilt virus (TSWV) by two thrips species, Frankliniella occidentalis and Frankliniella intonsa collected in green bell pepper fields in Oita Prefecture. Two populations of F occidentalis, Kokuragi and Koshoji, showed different transmission efficiencies (27.5% and 62.0%, respectively). An F. intonsa population collected in Koshoji transmitted the virus with a high efficiency (58.7%). These findings suggest that F. occidentalis and F. intonsa populations with high TSWV transmission efficiencies may play a role in severe epidemics of TSWV in green bell pepper fields in Oita Prefecture.

View full abstract

[in Japanese]

View full abstract

We ascertained the minimum amount of an alternative diet, Ephestia kuehniella eggs, that would allow the successful development and reproduction of Haplothrips brevitubus, a predacious natural enemy of thrips, under laboratory conditions at 25°C and 16-h light:8-h Dark. More than 70% of H. breuitubus larvae developed to adults when provided with 1.5 or 3.0 E. kuehniella eggs per individual daily. However. adult emergence rates decreased significantly when larvae were provided with 0.1 or 0.5 eggs daily. Similarly, the lifetime fecundity of H. brevitubus females was significantly higher at 1.5 or 3.0 eggs than at 0.1 or 0.5 eggs. Larval survival rates and female fecundity did not differ significantly between 1.5 and 3.0 eggs. These results indicate that the minimum amount of E. kuehniella eggs for successful rearing of H. brevitubus lies between 0.5 and 1.5 eggs per individual per day.

View full abstract

We studied the feeding ability and functional response of adult females of the predatory mite Neoseiulus californicus (McGregor) on greenhouse thrips. The females could attack 1 st instar larvae of Frankliniella occidentalis, but not 2 nd instar larvae, pupae, or adult females. The numbers of 1 st instar larvae of Foccidentalis, Thrips palmi, and Frankliniella intonsa consumed by the predatory mite increased as the prey density increased. The mean maximum predation rates per day against 1 st instar larvae were 7.1 F.occidentalis, 6.9 Tpalmi and 3.1 F intonsa. These result suggest that N. californicus is an effective natural enemy of these thrips.

View full abstract

[in Japanese]

View full abstract

We tested the effects of 40 insecticides, 11 acaricides, and 13 fungicides on adults of Aphidoletes aphidimyza (Rondani) (Diptera: Cecidomyiidae) by a residual-contact method in test tubes at 24± 1°C in the laboratory. Adults were reared in test tubes treated internally with aqueous dilutions of a pesticide. Some pesticides were also tested on middle-stage larvae by direct dipping. The period of residual toxicity of pesticides that showed high toxicity to adults was tested by rearing larvae on cucumber leaves on which pesticide had been sprayed beforehand. All insecticides showed toxicity to adults. The neonicotinoid group insecticides imidacloprid. nitenpyram, acetamiprid, and thiamethoxam showed high toxicity to adults, but three other insecticides in that group showed moderate toxicity. Chlorfenapyr, cartap, and spinosad showed high toxicity. Some or ganop hosp hate and pyrethroid pesticides showed high toxicity to larvae. Permethrin and chlorfenapyr showed high residual toxicity for more than 7 days after spraying. The residual toxicity of 11 other pesticides became low within 3-7 days. Insecticides in the insect growth regulator group except novaluron, acaricides except tebufenpyrad, fungicides, starch, tolfenpyrad, and indoxacarb showed low or no toxicity.

View full abstract

Obolodiplosis robiniae (Diptera: Cecidomyiidae) induces leaf-margin roll gall on Robinia pseudoacacia (Fabaceae). It is native to the northeastern states of the USA, but has been found recently in Japan, Korea, Italy. and the Czech Republic. In Japan, the gall midge has been collected from nine prefectures since its first discovery in Fukuoka in 2003. We found that the species is multivoltine in Japan, and adults emerge directly from the galls from early summer to autumn. Mature larvae of the final generation of the year seemed to quit the galls to overwinter on the ground. Further ecological and distributional information needs to be accumulated to clarify the pest status of O. robiniae. Because the pupa of O. robiniae was not intensively studied previously, its morphological features are briefly described as follows: pupal skin not pigmented: antennal sheath without apical horn: apical papillae each with 0.1 mm long seta: upper and lower frontal horns absent; a pair of lower facial papillae each with seta; prothoracic horn about 0.5 mm: very short stigmatal tubercles present on second to sixth abdominal segments; six dorsal papillae present on each of second to seventh abdominal segments: two outer papillae with seta: four inner papillae each with two tiny asetose circles.

View full abstract