The white grub beetle, Dasylepida ishigakiensis (Niijima et Kinoshita), is a serious pest of sugarcane in the Miyako Islands of Okinawa, Japan. Two evident electroantennographic (EAG) responses were observed by solid-phase microextraction sampling from female secretion and subsequent gas chromatography-electroantennographic detection (GC-EAD) analyses. These were identified as 2-propanol and 2-butanol by GC-MS analyses. GC-EAD on a chiral column showed two evident EAG signals corresponding to 2-butanol enantiomers, but the ratio and amounts could not be determined because of the small amounts. (R)-2-Butanol elicited the strongest EAG response, followed by (S)-2-butanol and 2-propanol, which showed 1/10 and 1/100 of the response of the first compound, respectively. In the field, only (R)-2-butanol attracted feral males when it was baited as 1 ml water solution of 1-100 mg of this compound, (S)-2-butanol, racemic mixture or 2-propanol on cotton ball lures (ca. 1.5 cm diameter) in vane-traps. When 2-propanol was blended with 10 mg/ml of (R)-2-butanol solution on cotton ball lures, male catches decreased as the amount of 2-propanol increased. From these results it was concluded that (R)-2-butanol was a component of the sex attractant pheromone of D. ishigakiensis while (S)-enantiomer and 2-propanol showed inhibitory effects when they were blended with the first compound.
On the main islands of Japan and in Taiwan, the spider mites Tetranychus kanzawai and T. urticae (green and red forms) are major pests on vegetable crops. The present study revealed that the dominant spider mite species injurious to vegetables in Okinawa, located between the main islands of Japan and Taiwan, differed from those in the two regions, providing important and fundamental information for controlling spider mites in Okinawa. T. okinawanus was the most dominant species throughout Okinawa with the broadest host range, even though the species has been regarded as a non-pest to date. T. piercei, which has similarly not been treated as a vegetable pest, was the second most dominant species with respect to frequency of occurrence and host range. T. kanzawai and T. urticae (green form) were comparable in the frequency of occurrence to T. piercei in the northern part of Okinawa (Okinawa Islands), whereas they were scarce in the southern part (Sakishima Islands). As other less-dominant species, T. ludeni, T. neocaledonicus and T. pueraricola were found infesting several vegetable crops. T. urticae (red form) was not found in this study.
Solanum fruit fly, Bactrocera latifrons (Hendel) is known as a pest of Solanaceae crops. This species is distributed throughout South-East Asia and has been discovered only on Yonaguni Island in Japan. After its first discovery in 1984 on Yonaguni Island, the species was found in 1985 and 1986, subsequently not detected for twelve years, and again discovered in 1999. We carried out a host fruit survey from 1999 to 2004 to monitor the occurrence of B. latifrons, and confirmed that B. latifrons has repeat generations within Yonaguni Island. During the survey, the number of sites where B. latifrons was found increased gradually, and eventually Yonaguni Island was entirely infested. So far, B. latifrons has not been found on neighboring islands. Most B. latifrons may overwinter at the adult stage on Yonaguni Island. In this survey, Diprocyclos palmatus was first recorded as the host of B. latifrons.
The monophlebid scale insect Icerya aegyptiaca is reported for the first time in the Ryukyu Islands of Japan, where it was found in four islands: Kurima Island, Kuro Island, Miyako Island and Yonaguni Island. Icerya aegyptiaca was collected from 36 plant species belonging to 23 families. Information on the distribution and natural enemies of I. aegyptiaca and a key to separate known species of Icerya occurring in Japan are provided.
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