施氮水平对普通大蓟马繁殖及子代性比的影响

Effects of nitrogen fertilization on reproduction and offspring sex ratio in Megalurothrips usitatus(Bagrall)(Thysanoptera:Thripidae)

为了评价施氮(N)水平对普通大蓟马(Megalurothrips usitatus)繁殖及其性比的影响,采用盆栽法种植豇豆(Vigna unguiculata),分别按低N(0 kg·hm^(-2))、中N(160 kg·hm^(-2))和高N(320 kg·hm^(-2))水平于苗前土施尿素,用叶盘法在室内单头饲喂已交配的1日龄雌虫,以嫩豇豆荚饲养其子代,观察亲代雌虫的繁殖与存活状况、子代的数量与性别。结果显示:与低N和中N处理相比,高N显著延长亲代雌虫的存活天数和产卵期,缩短产卵前期,提高产卵量和日产卵量。低N、中N和高N处理的子代雄性比分别为0.70、0.59和0.45,彼此之间差异显著。子代雌虫数量随施N水平的提高而增加,高N处理的子代成虫数显著大于低N和中N。施N对子代存活率没有影响。以上结果表明,施N水平能影响普通大蓟马的生长繁殖和性比,偏施N肥有利于普通大蓟马的繁殖,促使子代性比偏雌。

In order to evaluate the influences of nitrogen fertilization on reproduction and sex ratio of Megalurothrips usitatus(Bagrall),an economically important pest of legumes,the 1-day-old mated females were provided daily with leaf disks cut from the first leaves of potted cowpea at the age of 13 to 15 days,which were fertilized as a single pre-plant application with three different levels of urea at rates of 0,160,and 320 N kg·hm^(-2),respectively.After being checked the number of eggs,each leaf disk was transferred into a glass tube containing a section of young bean pod of cowpea,which was harvested from the field plants.Oviposition days of the focal females were recorded,and their offspring adult were sexed and counted.Sex ratios of offspring were calculated as proportion of males.The results showed that the females reared on leaf disks from plants fertilized with high N had significantly prolonged survival duration and oviposition duration,and shortened pre-oviposition period,and significantly greater oviposition rate and daily oviposition rate,compared to low N and medium N treatments.Offspring sex ratios for low N,medium N and high N treatments were 0.70,0.59,and 0.45,respectively,which were significantly different among each other.The number of offspring females produced by the females increased as N application rate increased.The number of offspring adults for high N treatment was significantly higher than those for low N and medium N treatments.N application level had no effect on immature survival of the offspring.In conclusion,nitrogen fertilization impacts on development,reproduction,and sex ratio of M.usitatus.Nitrogen overfertilization increases offspring production of this thrips,with a female-biased sex ratio.