A prediction model for strike in the sheep nasal fly, Oestrus ovis, in Namibia

A model was developed for predicting outbreaks of Oestrus ovis throughout the main sheep farming areas of Namibia. Pupal developmental periods were studied, concomitant air and soil temperatures enabling degree-day calculations to be made for prediction of adult fly strike. Monitoring of larval infection established seasonal incidence of O. ovis infestation and acted as verification of predictions. The establishment of relevant isothermal maps for Namibia made possible extrapolation from the several study sites to the entire sheep farming area. Retrospective and actual predictions of the important first peak after winter were considered accurate enough to recommend timing of control measures. No evidence of overwintering of first stage instars was found, the strategy used instead being extended pupation. Adult fly energy reserves were determined.     

X-ray Imaging of Stored Dates to Detect Infestation by Saw-Toothed Beetles

The objective of this study was to investigate the capability of X-ray imaging in detecting internal infestations caused by the saw-toothed beetle (Oryzaephilus surinamensis L.) in stored dates. Un-infested and infested dates were x-rayed for different life stages (egg, larvae, pupae, and adult) of O. surinamensis. An algorithm was developed to extract 44 features from the X-ray images. Linear discriminant analysis (LDA) was used to discriminate the un-infested and infested dates using extracted features. Overall accuracy of X-ray imaging system was 80% for un-infested and beetle-infested dates. X-ray imaging system yielded around 97% accuracy in detecting internal infestation of dates with an adult beetle while using a pairwise classification method. Further studies are required to investigate the effects of moisture content and hardness of dates in the discrimination between the un-infested and infested dates.     

Alternate crop and weed host plant oviposition preferences by the Mexican rice borer (Lepidoptera: Crambidae)

The Mexican rice borer, Eoreuma loftini (Dyar), is the key pest of sugarcane, Saccharum hybrids, in south Texas, having largely displaced the sugarcane borer, Diatraea saccharalis (F.), and it is moving into rice- and sugarcane-growing areas of east Texas and Louisiana. While a number of alternative weed and crop hosts have been reported, the extent to which they might support Mexican rice borer populations is unknown. This study involved choice assays that compared oviposition preference for and larval infestations of five mature graminaceous weed species. Levels of infestation between sugarcane and corn, Zea mays L., crop hosts and between corn and sorghum, Sorghum bicolor (L.) Moench, were also assessed. We determined that the average number of larval entry holes in sudangrass stems was ≥2.5-fold more than for any of the other four weed host plants, that corn had ≥5.9-fold more larval entry holes than sorghum and ≥8.2-fold more than sugarcane. Greater oviposition and infestation of one non-crop host over another was not related to numbers of stems per plant, but was associated with the greater stem diameter and abundance of dry leaf tissue found in Sudangrass, Sorghum bicolor (L.) Moench ssp. drummondi (Nees ex Steud.) de Wet & Harlan, johnsongrass, S. halepense (L.) and barnyardgrass, Echinochloa crus-galli (L.) P. Beauv.; relative to the other weed species in this study. In terms of the crop plants, stalk diameter and quantity of dry leaf tissue were not associated with numbers of eggs or larval entry holes in the choice assays between corn and sorghum, and between sugarcane and corn. While corn has been known as a host of the Mexican rice borer for at least 84 yr, its role in area-wide population dynamics and control efforts has likely been greatly underestimated.     

The distribution of <Emphasis Type="Italic">Obolodiplosis robiniae</Emphasis> on black locust in Slovakia

For the first time during October 2006, the occurrence of Obolodiplosis robiniae (Haldeman 1847) (Diptera: Cecidomyiidae) was recorded on the black locust (Robinia pseudoacacia L.) in Slovakia. During 2007, field surveys were undertaken to determine the distribution of the species and the infestation ratio at different locations. One year after its first discovery, O. robiniae was found throughout southern Slovakia. The gall midge was observed in 148 out of 161 checked locations. The infestation ratio of single leaves varied from 4 to 100%. The infestation ratio of the black locust tree was evaluated during May–June, July–August, and September–October, and accounted for 15–39, 9–53, and 6–49%, respectively. The most frequent infestation ratio fluctuated from 10 to 30% (115 locations). The highest infestation was recorded during July–August. Greater infestation was prevalent in the larger settlements than it was in the countryside. The gall midge was also recorded on R. viscosa Vent. Although the results show that O. robiniae is nowadays an usual insect with high potential to become an important pest of ornamental black locust or biological control agent against weedy black locust in southern Slovakia, the species do not appear to have reached pest status until now.     

The effect of artificial light treatment and depth on the infestation of the sea louse Lepeophtheirus salmonis on Atlantic salmon (Salmo salar L.) culture

Two field studies were carried out with farmed Atlantic salmon (Salmo salarL.) in sea cages to examine various effects of artificial light (AL) and the vertical distribution of salmon on lice infestation.

The use of AL light caused an overall increase in lice infestation in both experiments. The first study showed that salmon held at 0–4 m depth in cages developed higher infestation than salmon held at greater depths (4–8 and 8–12 m) under both natural light (NL) and AL. In the second study, salmon maintained in 14-m deep sea cages that were exposed to AL with different light intensities. The AL treatments resulted directly in different diel and seasonal patterns of vertical distribution of the salmon and also different temporal patterns in lice infestations. So indirectly the infestation pattern appeared to be correlated with median day-time swimming depth of the salmon.     

褐飞虱和白背飞虱在水稻品种上的为害特性

褐飞虱(Nilaparvata lugens Stal)和白背飞虱(Sogatella furcifera Horvath)均为国内各稻区的主要害虫。国内外有关稻飞虱为害发生的报道大多以单种飞虱为对象,然而这两种飞虱常年混合发生,且在水稻品种上的为害差异较大;因此,弄清这两种飞虱在不同类型水稻品种的为害特性及差异,对预测预报和合理防治稻飞虱具有较大的理论意义。作者于1988～1989年在浙江省农科院养虫室及萧山和桐庐病虫观察圃对两种飞虱在一些已推广和即将推广的水稻品种上的为害和发生特点进行了初步研究。     

Infectivity prospects of both nematodes and bacterial symbionts against cotton leafworm, Spodoptera littoralis (Biosduval) (Lepidoptera: Noctuidae)

A study was made on the susceptibility of the cotton leafworm, Spodoptera littoralis (Biosd.), to the nematode, Steinernema carpocapsae (All) and Heterorhabditis bacteriophora. Three concentrations of each nematode species were used (75, 150, and 300 infective juveniles) for each treatment. The nematode, H. bacteriophora, gave 100% mortality 96, 90, and 48 h, respectively, post-treatment of S. littoralis larvae with 75, 150, and 300 infective juveniles. On the other hand, S. carpocapsae (All) gave 100% mortality 120, 90, and 56 h post-treatment, respectively. Therefore, H. bacteriophora was more potent against cotton leafworm than S. carpocapsae. Studies on the infestation intensity of the nematode species against the cotton leafworm showed the predominance of H. bacteriophora over S. carpocapsae, while in studies of the reproductive rate those of S. carpocapsae predominate. The bacterial symbionts of each nematode species were isolated and tested alone against cotton leafworm at concentrations ranging between 1×10² and 5×10³ bacterial cells/larva. The results showed a higher activity of Photorhabdus luminescens than that of Xenorhabdu nematophilus.     

铃木氏果蝇研究进展

从铃木氏果蝇的分类地位、形态特征、生态习性、入侵及危害、经济损失和防治等几个方面综述了相关研究进展。     

稻纵卷叶螟为害损失率测定及经济阈值初步研究——Ⅲ.不同接虫量单因子试验结果及分析

试验于1982—1983年在湖南常德县蒿子港进行。供试品种“湘矮早9号”,每亩施纯氮10.25公斤,每小区6蔸禾,设6～9个不同接虫量处理,1982年8次重复,1983年6次重复;在幼穗分化第4期(6月13日)接虫。试验结果表明,试虫主要为害倒二、三两叶,基本上未为害剑叶,按每虫一般取食20cm~2计算,1982年每亩8.47万头虫造成2%的产量损失,1983年每亩8.96万头虫造成2%的产量损失,与本文第Ⅰ,Ⅱ报的结果基本一致。     

丹巴腮扁叶蜂生物学特性及为害调查

丹巴腮扁叶蜂(Cephalcia danbaica Xiao),自1987年由肖刚柔教授根据采自四川丹巴(桑地)的标本,定为新蜂种以来,迄今未见有关其生物学和为害的报道。近年来,该虫在青海部分林区为害相当严重,现将其发生情况记述如下。一、生物学特性 (一)寄主主要为害青海云杉(Picea crassifolia Kom.)亦加害华北落叶松(Larixprincipis-rupprechtii Mayr) (二)分布国内发生于四川(丹巴)、甘肃(武威),青海(大通),互助,湟中。大通县东峡林区是丹巴腮扁叶蜂的严重发生地,境内多青海云杉的片状纯林,海拔为2600-2800m。 (三)生活周期和主要习性 1.成虫发生期观察方法是在奇数年份,选择受害的云杉树,在其下用尼龙纱围绕基干扎成裙网,共计5个。在成虫出现前,每日检查一次,捉净网中当日羽化的成虫。这样直至羽化结束。据1989年定位观察,共查得成虫747头,其中雄蜂226头,雌蜂521头;