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Ecological studies on the bulb mites and their predators in Taiwan
|關鍵字:||Taiwan;臺灣;Bulb mites;Hypoaspis;Distribution;Life cycle;Predation;Toxicity;根璊;下盾璊;分布;生活史;捕食;藥劑毒性||出版社:||昆蟲學系||摘要:||
Investigations on the species and distribution of bulb mites were undertaken during 1994-2000. Results show that there are over 10 species of bulb mites belonging to Rhizoglyphus, Schwiebea, and Sancassania complex found in Taiwan. Among them, the most common species were found in the genus Rhizoglyphus including R. robini, R. setosus, R. echinopus, Rhizoglyphus sp.A, and Rhizoglyphus sp.B; certain species of the Sancassania complex and the genus Schwiebea are also common pests occurring in bulb gardens. R. robini and R. setosus were distributed almost over the entire island of Taiwan; Sancassania complex was found mostly in the central and southern parts of Taiwan; and the genus Schwiebea was distributed sporadically. In this study, it was found that records of host plants of bulb mites increased year by year; among them, 7 species of host plants were newly recorded in Taiwan for R. robini, 15 species for R. setosus, 7 species for the Sancassania complex, and 9 species for the genus Schwiebea.
The developmental time of R. setosus from egg to adult required 8 days at 28 ℃ when reared on artificial medium; the longevity of female and male adults was 23.79 and 23.30 days, respectively; the peak of oviposition appeared on the 6th day after female mating; and the total number of eggs laid by each female was 202.14, with an average of 7.95 eggs per day. For Rhizoglyphus sp.A the developmental time of the juvenile stage required 7 days at 28 ℃ when reared on artificial medium; the longevity of female and male adults was 24.27 and 22.21 days, respectively; the peak of oviposition appeared on the 4th day until the 8th day after female mating; and the total number of eggs laid by each female was 282.46, with an average of 11.86 eggs per day.
Species of predators of bulb mites were also investigated, and it was found that there are 9 families of predaceous mites in Taiwan including the Laelapidae, Parasitidae, Macrochelidae, Ascidae, Sejidae, Cunaxidae, Digamasellidae, Ologamasidae, and Rhodacaridae. Among them, the Laelapidae was the most common family occurring in the field; in this family, the genus Hypoaspis showed a high frequency of appearance and abundance, especially H. (Geolaelaps) aculeifer Canestrini and H. (Cosmolaelaps) A which were the most common predaceous species found in bulb mites colonies. From the close relationships of these 2 species and their prey genus, Rhizoglyphus, that occurred together in the same soil and living conditions, it is believed that H. (Cosmolaelaps) spp. and H. (Geolaelaps) spp. may become potential agents for controlling bulb mites.
For the predatory mite, H. aculeifer, the developmental time of the juvenile stage required 12 days when fed on protonymphs of R. robini at 28℃. The protonymphs and deutonymphs of H. aculeifer females could consume 4.75 and 8.34 protonymphs of R. robini, respectively, and males could consume 4.06 and 5.94, respectively. The longevity of female and male adults was 55.38 and 89.23 days, respectively; totally 184.38 protonymphs of R. robini were consumed by each female of H. aculeifer, with an average of 3.31 consumed per day; the peak of oviposition appeared on the 5-7th day after mating; and the total number of eggs laid by each female was 58.87, with an average of 1.72 eggs per day. For another major predatory mite, H. (Cosmolaelaps) A, the developmental time of the female and male were 8.52 and 9.31 days, respectively, when reared on the eggs of Bactrocera dorsalis at 28℃; the longevity of female and male adults was 31.91 and 41.65 days, respectively; the peak of oviposition appeared on the 4-8th day after mating; and the total number of eggs laid by each female was 47.17, with an average of 2.63 eggs laid per day.
The predation of H. aculeifer on 2 species of common bulb mites was tested in the laboratory; it was shown that females could daily consume 4.16 and 8.4 protonymphs, and 3.06 and 3.55 female adults of R. robini and R. setosus, respectively; and daily laid 1.4, 1.3 and 1.06, 1.1 eggs, respectively. The predation of H. aculeifer on R. robini and R. setosus were tested in the laboratory under different ratios of predator－prey densities. Under the ratios of 1: 5, 1: 10, and 1: 20, the predator was able to suppress the prey population effectively to a very low level, even to the point of almost eliminating them within 2-4 weeks; however, under the ratio of 1: 40, the predator could only depress the increase in the prey population, but could not destroy the prey. In a greenhouse, tests were run in pots of lily. Under these conditions and density ratios of 1: 10, 1: 20, and 1: 40, H. aculeifer could not destroy R. robini populations, but was able to depress the increase of prey populations to a certain low level, indicating that H. aculeifer is a good natural enemy that can be used in the biological control of bulb mites.
The toxicity of 13 insectcides/acaricides to R. robini, R. setosus, and R. echinopus was tested in the laboratory. Among them, 500 time diluter dazomet given the highest mortality to all 3 species; methyl parathion showed high toxicity to R. robini and R. echinopus; and ethoprophos was toxic to R. robini. The toxicities of 13 insecticides/acaricides and 18 fungicides to the predator H. aculeifer were also tested in the laboratory. Dazomet were diluted to 500 times given high mortality to H. aculeifer, and is not considered to be a good chemical agent for controlling bulb mites from the point view of protecting their natural enemies; however, the other 12 pesticides showed very low toxicity to this predator. All 18 fungicides tested in this study showed less than 20% toxicity to H. aculeifer. All of these chemicals with low toxicity that are safe to predatory mites are available for use in the management of bulb mites.
自1994年6月至2000年3月止調查臺灣地區根之種類及其分布，結果發現臺灣地區發生的根有10種以上，分別屬於根屬(Rhizoglyphus)、士維屬(Schwiebea)及Sancassania complex等，其中以根屬最為常見，分布亦最廣泛，主要包括羅賓根(R. robini)、長毛根(R. setosus)、刺足根(R. echinopus)、Rhizoglyphus sp. A及Rhizoglyphus sp. B，而士維屬與Sancassania complex之發生亦日趨普遍。根在臺灣地區之分布相當普遍，其中羅賓根與長毛根幾乎遍佈全台，Sancassania complex以中、南部發生較多，士維屬則為零星分布。根在臺灣地區為害之寄主植物年有增加的趨勢，羅賓根可為害21種寄主植物，其中新記錄種有7種之多，長毛根可為害21種寄主植物，其中新記錄種更高達15種，Sancassania complex之寄主植物有11種，其中7種為新記錄種，而士維屬可為害13種寄主植物，其中有9種為新記錄種。
長毛根於28℃定溫下以人工飼料飼養，自卵發育至成約需8日，雌、雄成壽命分別為23.79日及23.30日。雌成在交尾後第6日達到產卵高峰，每隻雌成一生平均產202.14粒卵，平均每日產7.95粒。Rhizoglyphus sp. A自卵發育至成約需7日，雌、雄成壽命分別為24.27日及22.21日。雌成在交尾後第4日達到產卵高峰，此高峰期維持至第8日，每隻雌成一生平均產282.46粒卵，平均每日產11.86粒。
根天敵之種類經調查共有厲科(Laelapidae)、寄科(Parasitidae)、巨螯科(Macrochelidae)、囊科(Ascidae)、綏科(Sejidae)、巨須科(Cunaxidae)、雙革科(Digamasellidae)、土革科(Ologamasidae)及胭科(Rhodacaridae)等9科之捕食性類，其中以厲科最為常見，分布亦最廣泛。厲科中以下盾屬(Hypoaspis)田間發生之頻率最高，尤以尖狹下盾(H. (Geolaelaps) aculeifer Canestrini)及廣厲A( H. (Cosmolaelaps) A)最為常見。由根與天敵之共棲關係顯示H. (Cosmolaelaps) spp.及H. (Geolaelaps) spp.之發生均與根屬有密切關聯性，是為根類可供有效利用之自然天敵。
室內測試13種殺蟲()劑對羅賓根、長毛根及刺足根之毒性，85% dazomet W. P.之500倍稀釋液對三種根均具高致死率，40% methyl parathion C. S.對羅賓根及刺足根甚具毒效，70.6% ethoprophos G.對羅賓根亦具毒殺效果。室內測試13種殺蟲()劑及18種殺菌劑對尖狹下盾之毒性，其中除85% dazomet W. P.之500倍稀釋液對尖狹下盾具高毒效，而不宜利用外，其餘各藥劑對尖狹下盾均為低毒性，用以防治病害之殺菌劑對尖狹下盾之致死率均低於20%，皆為低毒性而安全性高之藥劑，適供綜合防治時之選擇。
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