甘肃环县两种沙打旺蛀秆害虫数量随季节、年份和草地年龄的变化动态

沙打旺是我国北方主要的豆科牧草和水土保持植物,害虫是其生产的限制因素之一,其中沙打旺小食心虫（Crapholita shadawana）（卷蛾科）和沙打旺黑潜蝇（Melanagromyza adsurgenis）（潜蝇科）为重要的蛀秆害虫。本研究于2004年、2005年和2006年8月或9月以及在2005年5月（返青后期）、6月（拔节期）和8月（开花初期）调查了甘肃环县4个年份（1998年、2000年、2002年和2003年）建植的沙打旺草地上此两虫的发生规律,发现其发生与年份、草地年龄和季节有关,两虫分别为害3龄以上（含3龄）和8龄以下（含8龄）沙打旺,植株被害率分别为20.0%~100.0%和52.0%~100.0%,其中2005年发生最普遍,植株被害率均为100%。虫口数量随年份变化,其中在年龄最大（1998年建植）和最小（2003年建植）的草地上,沙打旺小食心虫在2006年时的百枝虫量均显著（P<0.05）低于其他两年,而在其他年龄的草地上则均显著（P<0.05）高于其他两年,3年中最高达65.8头·百枝-1（即65.8%的枝条受害,1998年建植2004年数据）;沙打旺黑潜蝇在2006年时在年龄最小草地上显著（P<0.05）高于其他年份,在年龄最大草地上则显著低于（P<0.05）其他年份,3年中最高达38.8头·百枝-1（即38.8%的枝条受害,2000年建植2004年数据）。基于4个年度建植的草地在调查年份中年龄与百枝虫量的关系可知,总体上,两虫的虫口数量均随着草地年龄的增加而增加（年度有波动）,分别于7龄和8龄时达到高峰,此后随着草地的衰退而急剧下降。在同一年份的不同生长季节,两虫均于6月开始为害（5月时未见发生）,但沙打旺小食心在6月时仅出现在年龄最大草地,在各龄草地上8月的百枝虫量显著（P<0.05）高于6月,而沙打旺黑潜蝇6月时百枝虫量已达最大值,除年龄最小草地外均显著（P<0.05）高于8月。在同一枝中未发现2种害虫,也未发现2头或2头以上的同一害虫。受害枝条外观与未危害枝条无明显差异,故剖茎观察虫体、虫洞和虫粪是判别枝条是否受害的主要方法。甘肃省为此两虫的新分布省份。     

Seasonality of Eurytoma sp.—a parasitoid on okra petiole maggot,Melanagromyza hibisci Spencer

Abstract

Studies on the seasonal abundance of Eurytoma sp. a parasitoid on okra petiole maggot, Melanagromyza hibisci Spencer were conducted for one year. Per cent parasitism ranged from 10 to 68 during the study period. However, there was no significant relationship between percentage parasitism on host density. Data further revealed that parasitoid response to host density was weak.     

Soybean stem fly,Melanagromyza sojae (Diptera: Agromyzidae), on Sumatra: Seasonal incidence and the role of parasitism

Abstract

The density of M. sojae and percentage parasitism was studied in unsprayed soybean at 18 farmers’ field sites in Aceh, North Sumatra and West Sumatra provinces, Indonesia, during 1992 and 1993. M. sojae generally infested soybean throughout the season; infestation was initially low, reached its peak from the fifth till the eighth week after planting and declined towards the end of the season. A complex of seven hymenopterous parasiloids had a high impact on the pest. Parasitism levels built up alongside with host density and remained high until just before harvest. The eucoilid Gronotoma sp. was the most prevalent species during the early and mid‐season; a complex of pteromalids became dominant towards the end of the season. In soybean planted successively at 2‐week intervals, the parasitism level in the first‐planted crop built up slowly, whereas the parasitism level in the third‐planted crop was high from the early crop stage onwards, which suggests that the third‐planted crop benefited from parasitism build‐up in the earlier‐planted crops. The role of parasitoids in controlling beanflies in unsprayed soybean is discussed.     

Physico-chemical traits of Cajanus cajan (L.) Millsp. pod wall affecting Melanagromyza obtusa (Malloch) damage

Pigeonpea [Cajanus cajan (L.) Millsp.] is an important legume crop in the semi-arid tropics, and pod fly [Melanagromyza obtusa (Malloch)] is an important emerging constraint to increase the production and productivity of this crop under subsistence farming conditions. Host plant resistance can be used as an important tool for the management of this pest. Therefore, a set of ten pigeonpea genotypes from a diverse array of plant growth types and maturity groups including two appropriate commercial checks, was evaluated for resistance to pod fly under field conditions, and characterized for physico-chemical pod traits. The non-determinate type GP 75 (extra early maturing) and GP 118 (early maturing), and determinate type GP 233 (extra early maturing) and GP 253 (early maturing) genotypes had significantly lower pod and seed damage as compared to determinate (Prabhat) and non-determinate (Manak) early maturing checks, suggesting that resistance to pod fly is not linked to plant growth type and maturity period of the genotype in pigeonpea. Pod wall thickness, trichome density, reducing and non-reducing sugars, total phenols, tannins, and crude fiber were found to be negatively associated (r = −0.83** to −0.97**), while total protein positively associated (r = 0.88** to 0.97**) with pod fly infestation. Therefore, these traits particularly total phenols, tannins, crude fiber, trichome density, and pod wall thickness, can be used as physico-chemical markers to identify pigeonpea genotypes with resistance to M. obtusa, and use in pod fly resistant breeding program in pigeonpea.     

Weeds and Shifting Cultivation

Abstract

Traditional labour-intensive methods of weed control which are normally associated with shifting cultivation are evaluated and compared with the use of herbicides and improved cultural practices. Problems occurring in shifting cultivation, such as weed seed dormancy, erosion and changing weed population; and methods of reducing the weed problem are discussed.     

晋南夏播大豆豆秆黑潜蝇发生规律及防治技术研究

山西南部危害夏播大豆的豆秆黑潜蝇基本上有三个世代，豆秆黑潜蝇的防治方法是从7月初开始喷药，每隔10天喷一次，连续喷四次，防效比较好。     

大豆抗豆秆黑潜蝇性能的研究 Ⅳ.豆秆蝇各虫态历期和不同日龄幼虫的特征与蛀害习性

应用软X射线拍摄结合人工接种和系统剥查方法,查明豆秆黑潜蝇在7月下旬至8月份发生期间的各虫态历期,幼虫蛀入主茎的节位与途径,各日龄幼虫为害主茎的虫道长度与形状以及各日龄幼虫的特征。所有这些可供大豆品种抗蝇性鉴定之用。