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RISS 인기검색어
- 검색키워드
- 저자 : Visarto, Preap (검색결과 4 건)
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Visarto, Preap,Zalucki, Meron.P.,Nesbitt, Harry J.,Jahn, Gary C. Korean Society of Applied Entomology 2001 Journal of Asia-Pacific Entomology Vol.4 No.1
Uneven farm practices between farmers cause the patchy pest distribution, especially in the brown planthopper (BPH: Nilaparvatalugens(St${\aa}$l)) in Cambodia. Sine 1994 BPH have attacked Cambodian rice fields in patchy form. Moe BPH attacked in field where farmers have more opportunity to use fertilizer and insecticides. Rice production in Cambodia will probably face more problems with BPH outbreaks as rice production intensifies. The birth and/or survival rate of BPH that leads to population outbreaks are related to fertilizer, plant variety and insecticide treatments. The experiments were conducted in the field and laboratory in Cambodia in 1999 to test the hypothesis above. A traditional variety (Eath Chhmoush), low and high fertilizer rates, and an organic phosphate insecticide (Diazinon)ere used in the field experiment and two varieties(susceptible and tolerant to BPH) and three rates of NPK fertilizer were used in the laboratory study. BPH population and others arthropods wre collected weekly from the field experiment a D-vac machine. Two kinds of net cages (temporary and permanent) were covered the rice plants to determine the birth and survival rate of BPH population with and without natural enemies. Number of O cytes was counted from BPH females, which reared in plant-cages. Birth and survival rates of BPH were higher in susceptible plant with high fertilizer rate used. The experiment indicated that natural enemies have played the important role to control the BPH population. The realized fecundity and survival of BPH was higher in susceptible host plant variety with high rate of NPK feritlizer used. The immediate response of fertilizer application to the BPH offspring production was not shown and will be tested in wet season 2000.
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Preap, Visarto,Zalucki, Myron P.,Jahn, C.,Nesbitt, Harry J. Korean Society of Applied Entomology 2001 Journal of Asia-Pacific Entomology Vol.4 No.2
The most abundant natural enemies found in Cambodian rice field are spiders, mostly Araneus inustus and Pardosa pseudoannulata. These two hunting and wolf spider, respectively, are believed to actively contribute to brown planthopper (BPH) population control. However, how much each species attacks prey in Cambodian field condition is unknown. We conducted field experiments in Cambodia during the wet season at two locations, a farmer\`s fields at Takeo and at CARDI, using both field cages and natural conditions. Cages were sprayed with insecticide to remove all pre-existing insects in the cages and then washed after 10 days to reduce insecticide residue. Results confirmed BPH inside the cage were killed by the insecticide. A known BPH population was reared inside the cages starting with 3 pairs of adults. Temporary cages were removed after counting second instar BPH and permanent cages were left in place. Spiders were released into the cages for 15 days. In permanent cages either two individual A. inustus or P. pseudoannulata were allowed to feed on BPH prey. Both spider species have the same killing ability in dense prey populations, but predation is higher for Pardosa at low prey density. In uncaged field environments (where more than just BPH prey are available) with a spider/BPH ratio 1:3 to 1:11 BPH mortality was 78-91%. Within 15 days in permanent cages spiders caused 100% BPH mortality at an average predator/prey ratio of 1:5 to 1:14. At a ratio of 1:18 or higher there was some BPH survival in cages.
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Establishment of Nilaparvata lugens Stal in Rice Crop Nurseries: A Possible Source of Outbreaks
Preap, Visarto,Zalucki, Myron P.,Jahn, Gary C.,Nesbitt, Harry J. Korean Society of Applied Entomology 2002 Journal of Asia-Pacific Entomology Vol.5 No.1
We tested the hypothesis that early-planted seedbeds of rice are more heavily infested with brown planthopper (BPH) than later seedbeds, and that transplanted plants with BPH are a source of subsequent population increase and possible outbreaks. The experiments were conducted at CARDI and Takeo province in wet season 2000 and early wet season 2001. BPH at 0, 25, 50, 100, 200 /$\textrm{m}^2$ were infested onto plants with low and high fertilizer treatments. Rice seeds of varieties moderately and highly susceptible to BPH were sown 3 weeks early, 2 weeks early, at the normal time, and later than normal (5 weeks) and treated with low and high fertilizer rates. At Takeo, the 3 weeks early seedbeds were infested by BPH migration, and both varieties with high fertilizer caught more immigrant insects and subsequently had damaging outbreaks of BPH in the third generation. At CARDI, no seedbeds were infested with immigrant BPH. Seedbeds in areas with continuous cropping of rice have a high risk of BPH attack. Seedlings infested wish 200, 100, and 50 BPH/$\textrm{m}^2$ resulted in death of the plant. Plants with 100 and 200 BPH/$\textrm{m}^2$ were killed sooner. With 25 BPH/$\textrm{m}^2$ plants were not killed, but subsequent population increase caused yield reduction. Yield loss was high in high fertilizer treated plants.
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