【摘要】 1976—1977年河北晋县贺家寨大队小麦春季灰飞虱的传带病毒率为31—52%,不同地块同代灰飞虱的带毒率异差较大:而秋苗期则为12—35.4%,其中不同地块上同代(四代成虫)灰飞虱的带毒率的差异从33.3%至35.4%则不太大。灰飞虱的有效传毒指数(即虫口数×自然带毒率)同田间小麦发病率的相关性是非常显著的,其r=0.9769。1975—1976两年调查及计算分析结果,其直线回归公式如y=4.12x-2.577。在有效传毒指数0.7—20.9之间用于予测发病率有效。人工分期侵染试验证明小麦在生长发育过程中受侵愈早,病情愈重,其中死株率也愈大。秋季侵染的死株率达95.6%,病指为99.6;夏季侵染的死株率为0,病指为57.6。秋季小麦出苗前后的大量虫口形成小麦10月中下旬的一个发病高峰,第二年春季4月中旬的虫口高峰形成5月上旬的一个发病高峰。3月下旬的一个发病高峰是越冬前受侵的。病毒在小麦植株中的潜育期的长短随小麦的生长速度而异。温度不过其中因素之一,最短5—8天,最长30—40天。侵染后如小麦进入越冬期,即不表现症状,一直要到返青以后。介体灰飞虱在河北晋县以第五代3—4龄若虫在冬麦地及草荒中越冬。夏季在玉米上可以产卵并孵化,但不能长期存活,主要在地头沟边及夏作物荫蔽下的禾草上越夏。冬麦治虫防病的重点应在秋季麦苗出土前,春季则应在3月中旬左右。冬麦适当推迟播种有利于减少发病率。棉间作麦比平作的病情重六倍而粮麦间作的病情比平作的重九倍。更多还原

【Abstract】 During 1976 to 1977 the percentage of the viruliferous planthoppers(Laode-lphax strietellus)in Hojiazhai,Hobei province was surveyed.In spring it was 31-52%while in autumn 12-35.4%.The percentage varied significantly in the coll-ections from various localities but not from the same locality,A correlationwas demonstrated between the indices of effective transmission(number of plant-hopper collected x % of viruliferous individuals)and % diseased plants.Onbasis of the data obtained during the field surveys during 1975 to 1976,a regressioncurve was plotted and the formula was calculated as Y=4.12x-2.577.Wherethe r=0.976.Therefore the correlation was considered as very significant.If the indices of effective transmission between 0.7-20.9 were employed to cal-culate the % disease plants to develope later in the growing season,an epiphyto-tics would be possible to be forecasted.Inoculation tests revealed thatthe earlier the infection takes place,the more severe will be the disease develop-ment.Infections took place in the early seedling stage of wheat plants usuallyled to the death of the plants,Therefore the early autumnal infections mightresult as high as 95.6% of death while the spring infections caused no deathof plants and a lowr disease index 57.6。There were two migration peakes ofthe insect vectors.The one was in the early part of november when he winter wheatwere in at state of emergence or just at the early seedlihg stage.This infectionled to a peak of disease development in the later of november.The other peakof migration was in the mid of april when the wheat was just after overwinter-ing.This spring infection led to another peak of disease development in May,however it caused less damage.The length of incubation period of the virus(NCMV)in the winter wheat plants varied with the time of infection,especia-lly with the growth activities of the wheat plants.It ranged from 5-8 daysand 30-40 days.If the infection took place just before overwintering of thewheat plants,the symptoms did not appear unitl the next spring.The insect vectorstided over winters in the form of 3-4 star nymphs of the 5th generation underthe winter wheat plants or ofe ggs on grasses.They oversummered in fields of sum-mer crops.Although they were able to oviposit on corn plants yet they couldnot subsist on it.The disease became more prevalent where the intercroppingsystem of winter wheat and-corn or sorghum or cotton had been practiced,since the grass weeds under the summer crops provided a favorable ground forthe insect vectors as well as the virus to multiply.更多还原