Can polycultural manipulation effectively control rice planthoppers in rice-based ecosystems?

Rice planthoppers (mainly Nilaparvata lugens (Stål) and Sogatella furcifera Horvath) are the most destructive rice pests throughout southeastern and eastern Asia. Planthopper feeding often causes “hopper burn” and reduces rice yields. Currently, insecticide use is the sole pest management option available to most Chinese farmers. Because pesticide use may have undesirable effects, environmentally sound and sustainable management alternatives are urgently needed. In a two-year field study at the Wuyishan Experimental Station of the Institute of Applied Ecology (IAE), Fujian Agriculture and Forestry University (FAFU), we evaluated the effects of polycultural manipulation on the abundance, sexual differentiation and wing dimorphism of rice planthoppers. The polycultural manipulation was arranged in mosaic patterns of paddy plots intercropped with non-paddy plots including chili pepper, ginger, maize and peanut plants. Monocultural fields of paddy plants were used as controls. Polycultural manipulation significantly reduced the abundance of total planthoppers and nymphs of N. lugens and S. furcifera. The number of overall planthoppers decreased on average by 49% and 55% in 2007 and 2008, respectively. However, polycultural manipulation had no impact on the proportions of female or macropterous planthoppers. The resource concentration and associational resistance hypotheses may explain these results. In polycultural fields, non-rice species may mask the chemical or visual attractants of rice, making them less apparent, and microhabitat differences in the levels of secondary compounds or in plant quality may also disrupt planthopper orientation.     

Feeding behaviour of whitebacked planthopper, Sogatella furcifera (Horvath), on resistant and susceptible rice varieties

Feeding behaviour of the whitebacked planthopper Sogatella furcifera (Horvath) was studied on 30-, 45- and 60-day-old plants of seven resistant varieties and one susceptible variety of rice. The preference or otherwise of the hoppers to different varieties was studied in terms of the feeding marks made and the amount of honeydew excreted. The insect made more feeding marks and excreted less honeydew on resistant varieties than on the susceptible TN 1. The number of feeding marks increased with the increase in the plant age of varieties, while the honeydew excretion decreased.     

Sequential sampling: planthoppers in rice

A sequential sampling plan was developed for the brown planthopper, Nilaparvata lugens Stal, and the whitebacked planthopper, Sogatella furcifera Horváth in rice. The plan was tested in several different areas in the Philippines and compared with a more intensive sampling technique. Results showed a 100% agreement between the two techniques in decision-making, and an 80% saving in time was realized using the sequential sampling plan.     

Transmission characteristics of Southern rice black-streaked dwarf virus by rice planthoppers

Southern rice black-streaked dwarf virus (SRBSDV) is a recently proposed distinct species in the genus Fijivirus, family Reoviridae. During the past decade, SRBSDV has spread throughout southern China and northern Vietnam, and has become one of the greatest threats to rice production in these regions. We evaluated three common planthopper species affecting rice: white-backed planthopper (WBPH, Sogatella furcifera), brown planthopper (BPH, Nilaparvata lugens) and small brown planthopper (SBPH, Laodelphax striatellus) to determine their virus transmission abilities. It was confirmed that WBPH was an efficient persistent-transmitting vector for SRBSDV. Neither BPH nor SBPH were viral vectors, although a small proportion (3.7%) of tested SBPH acquired the virus from diseased rice. We characterized the virus transmission properties of WBPH. 83% of the tested insects fed on virus-infected rice plants became viruliferous. The minimum virus acquisition and inoculation access periods were 5 and 30 min, respectively, for both WBPH nymphs and adults. The circulative transmission periods of the virus in WBPH ranged from 6 to 14 days, and most viruliferous individuals transmitted the virus in intermittent periods ranging from 2 to 6 days. A single individual of WBPH could infect 8–25 rice plants with the virus in a 5-day period. WBPH could transmit SRBSDV from rice to maize seedlings, but it was barely able to acquire the virus from infected maize. These results improve our understanding of the epidemiology of SRBSDV, and will be useful for development of disease control strategies.     

Varietal resistance in rice against Sogatella furcifera (Horváth)

The whitebacked planthopper, Sogatella furcifera (Horváth) (Homoptera: Delphacidae), is emerging as a serious pest of rice in many countries. Because of the increased economic importance of the insect and the difficulty of controlling it with insecticides, incorporation of natural resistance to S. furcifera has become a major objective of the rice improvement programme at the International Rice Research Institute. Several research centres in national rice improvement programmes in India, Indonesia and Korea are also currently screening germplasm for resistance to S. furcifera. Literature documenting the status of research on varietal resistance and the current strategy in germplasm evaluation and breeding programme is reviewed. Rice varieties resistant in various countries and sources of resistance used in breeding are listed. Varieties with multiple resistance to different leafhopper and planthopper pests are also listed. The mechanism and the inheritance of resistance in rice varieties are reviewed. The possibility of biotype development is discussed and future strategies in such an eventuality are pointed out.     

Evaluation of rice accessions for resistance to the whitebacked planthopper Sogatella furcifera (Horváth) (Homoptera: Delphacidae)

Rice, Oryza sativa L., and wild rice accessions from the world collection were evaluated for resistance to the whitebacked planthopper, Sogatella furcifera (Horváth). Of 48554 O. sativa accessions from 96 countries, 401 (0·8%) were selected for resistance and 351 (88%) of these were from Nepal, India, and Pakistan where S. furcifera is a serious pest. However, some resistant accessions originated from regions beyond the distribution of S. furcifera. Many of the wild rice accessions, consisting of 28 species primarily from the O. minuta Presl., O. nivara Sharma et Shastry and O. officinalis Wall groups, were resistant. Although no S. furcifera-resistant commercial cultivars have been released, advanced breeding lines with resistance to S. furcifera and other major insect pests have been developed.     

烯效唑对稻飞虱取食和产卵行为的影响

烯效唑对稻飞虱取食和产卵行为的影响刘光杰,赵伟春（中国水稻研究所,杭州３１０００６;浙江农业大学,杭州３１００２９）关键词：烯效唑;白背飞虱;褐飞虱;取食产卵;抗虫性ＩｎｆｌｕｅｎｃｅｓｏｆＵｎｉｃｏｎａｚｏｌｅｏｎｔｈｅＦｅｅｄｉｎｇａｎｄＯｖｉｐ...     

Relative toxicity of insecticides to rice planthoppers and leafhoppers and their predators

The relative toxicity of 20 rice insecticides to the brown planthopper Nilaparvata lugens (Stål), whitebacked planthopper Sogatella furcifera (Horváth), green leafhopper Nephotettix virescens (Distant) and their predators, the wolf spider Lycosa pseudoannulata (Boes et Str.) and the mirid bug Cyrtorhinus lividipennis (Reuter) was determined by the topical application method. Relative toxicity was based on the LD₅₀ value for each chemical, using the predator divided by the LD₅₀ value obtained using the hoppers. Relative toxicity ratios of the insecticides varied greatly, depending upon the predator:pest combination. Deltamethrin was highly toxic to L. pseudoannulata and C. lividipennis whereas ethylan was 65 and 21 times more toxic to N. lugens than to the two predators, respectively. Overall, ethylan had the highest relative toxicity ratio of the 20 insecticides, being safest to the two natural enemy species.     

中国杂交稻组合汕优63上白背飞虱多发生的成因探讨

以汕优63及其亲本、常规稻春江11为材料,研究了白背飞虱在中国杂交稻品种汕优63上大量发生的主要原因.从杂交稻汕优63和常规粳稻春江11上白背飞虱的发生情况来看,白背飞虱长翅型雌成虫的迁入密度和产卵数没有明显差异,种群的变化也一致.但汕优63的卵孵化率较高,若虫种群密度也明显较高.从汕优63及其亲本对白背飞虱的反应来看,汕优63的恢复系明恢63抑制白背飞虱的繁殖,但不育系珍汕97A和保持系珍汕97B对白背飞虱繁殖有促进作用.珍汕97A和汕优63的稻-飞虱间的干物质转化率基本相同,但汕优63具有较高的干物质生产能力,可能使白背飞虱繁殖密度较高.日平均蜜露分泌量,以珍汕97A和珍汕97B最多,明恢63最少,汕优63居中.珍汕97A的筛管液中大部分是主要氨基酸,浓度高于汕优63和明恢63.汕优63与明恢63的筛管液中氨基酸的总浓度基本相同,但微量氨基酸浓度高于明恢63.总的来看,汕优63的白背飞虱繁殖率较高,主要原因在于不育系珍汕97A的高感虫性和杂种优势的高干物质转化能力产生的耐受性,而不是珍汕97A的白背飞虱感虫性和细胞质不育导致的.     

Density,Demography, and Influential Environmental Factors on Overwintering Populations of Sogatella furcifera (Hemiptera: Delphacidae) in Southern Yunnan,China

Sogatella furcifera (Horváth) (Hemiptera: Delphacidae) is the most serious pest on rice in southwestern China. Yunnan province is within this region and is a major overwintering area for S. furcifera in China. This field study was carried out over 4 yr (2010–2013) and focused on S. furcifera distribution, population density, and demography, as well as the relationship between various environmental factors and the distribution and density of overwintering S. furcifera in Yunnan. Our study demonstrated that overwintering populations of S. furcifera mainly occurred in valleys and lowlands below 25.02°N and 1,680 m above sea level (a.s.l.), where ratooning rice was present. The overwintering range of S. furcifera has expanded in Yunnan compared with 20 yr ago, and regional climate change is believed to be the main contributing cause for this expansion. Environmental factor analysis showed that the mean air temperature of the coldest quarter and precipitation of the coldest quarter were two key factors that were strongly linked to the overwintering distribution and density of S. furcifera in Yunnan. Wintertime temperature was the principal influencing factor to determine the distribution and density of S. furcifera, while the effect of precipitation was indirect in that it influenced the insect’s distribution via its host. This study documented the major overwintering areas of S. furcifera in Yunnan, which can be used to predict outbreak potential in the following spring. Hence, key climatic factors, overwintering distribution, and density of S. furcifera should be used when forecasting outbreaks in spring.     

Characterization of 12 Novel Microsatellite Markers of Sogatella furcifera (Hemiptera: Delphacidae) Identified From Next-Generation Sequence Data

The white-backed planthopper, Sogatella furcifera (Horváth) (Hemiptera: Delphacidae), is a major pest of rice and has long-range migratory behavior in Asia. Microsatellite markers (simple sequence repeats) have been widely used to determine the origins and genetic diversity of insect pests. We identified novel microsatellite loci for S. furcifera samples collected from Laos, Vietnam, and three localities in Bangladesh from next-generation Roche 454 pyrosequencing data. Size polymorphism at 12 microsatellite loci was verified for 40 adult individuals collected from Shinan, South Korea. The average number of alleles per locus was 7.92. The mean values of observed (H_o) and expected heterozygosities (H_E) were 0.615 and 0.757, respectively. These new microsatellite markers will be a resource for future ecological genetic studies of S. furcifera samples across more broad geographic regions in Asia and may assist in estimations of genetic differentiation and gene flow among populations for implementation of more effective management strategies to control this serious rice pest.     

Insecticide-induced resurgence of the whitebacked planthopper Sogatella furcifera (Horvath) (Hemiptera: Delphacidae) on rice varieties with different levels of resistance

The influences of the insecticides quinalphos, chlorpyriphos, methyl parathion, endosulfan, imidacloprid and deltamethrin applied three times at 10 days intervals at half of their recommended field concentrations to potted plants of a planthopper-susceptible and a planthopper-resistant rice variety, on reproduction and survival of whitebacked planthopper, Sogatella furcifera (Horvath), and on the chemistry of its host plant, were investigated. Methyl parathion, deltamethrin and quinalphos enhanced the fecundity of the hopper (164-211 vs. 131 for the control) and consequently the resurgence ratio (increased up to 1.75 fold). Methyl parathion and deltamethrin significantly increased nymphal survival (59.3 vs. 52.2% for the control) and the growth index (4.8 vs. 4.2 for the control) of the hopper. The sex ratios of adults emerging on methyl parathion- and deltamethrin-treated rice plants increased in favour of females (1.51 vs. 1.15 for the control) on the susceptible variety but was not altered on the resistant variety. Biochemical analyses of the rice leaves revealed significantly higher quantities of reducing sugars, proteins and amino acids, but lower amounts of total phenols in leaf sheaths and blades of methyl parathion-, deltamethrin- and quinalphos-treated plants of the two varieties. The leaf sheaths and blades of the resistant variety contained more than twice the total phenols present in those of the susceptible variety. The results showed a positive correlation between increased levels of reducing sugars, amino acids and proteins in the rice plants and the fecundity of S. furcifera and a negative correlation between phenol contents of the rice plants and fecundity.     

Field evolution of insecticide resistance in the brown planthopper (Nilaparvata lugens Stål) in China

The brown planthopper (Nilaparvata lugens Stål) is one of the most destructive pests of rice crops in Asian countries including China, Vietnam, Thailand, etc. Evolution of resistance in this pest insect to isoprocarb, buprofezin, pymetrozine, imidacloprid and other neonicotinoid insecticides has been reported. In order to investigate the current status of resistance to commonly used insecticides, nine field populations of N. lugens were collected from Central China, East China and South China, and resistance to insecticides was monitored from 2009 to 2012. All the 9 field populations collected in 2012 had developed extremely high resistance to imidacloprid, with resistance ratios (RR) ranging from 209.3 to 616.6. Resistance to imidacloprid was much higher in 2012 than in 2009. The RR of thiamethoxam varied from 17.4 to 47.1, and the RR of nitenpyram varied from 1.4 to 3.7 in 2012. Of the 9 field populations, six populations showed higher resistance to nitenpyram in 2012 than in 2011. RR for buprofezin varied from 110.1 to 221.6 in 2012 whereas resistance was at a medium level (RR 20.4 ∼ 39.4-fold) in 2009. RR for pymetrozine ranged from 34.9 to 46.8 in 2012. As for isoprocarb, RR ranged from 21.7 to 38.1 in 2012. The obvious increase in resistance to widely applied insecticides indicates that insecticide resistance management strategies are urgently needed to prevent or delay further increase of insecticide resistance in N. lugens.     

High Temperature Modifies Resistance Performances of Rice Varieties to Brown Planthopper,Nilaparvata lugens(Stl)

To investigate the effect of temperature on the resistance characteristics of rice varieties with different resistance genes to brown planthopper(BPH),Nilaparvata lugens(Stl),the resistances of IR26(Bph1)and IR36(bph2)to BPH population in Hangzhou,China were monitored in greenhouse during September in 2007 and 2008 by using the standard seedling screening techniques(SSST)developed by the International Rice Research Institute(IRRI).Furthermore,the changes in resistance of IR26 and IR36 to BPH,soluble sugar and oxalic acid contents in 25-day-old rice plants of susceptible variety TN1 and resistant varieties IR26 and IR36 were detected at five temperatures(22℃,25℃,28℃,31℃ and 34℃).IR26 completely lost resistance both in greenhouse and at the five tested temperatures.IR36 still had moderate resistance at natural temperature,but its resistance decreased gradually when the temperature increased from 25℃ to 34℃,and fully lost its resistance at 31℃ and 34℃.The highest durable resistance of IR26 and IR36 were recorded at 25℃.The soluble sugar content in plants of the three tested rice varieties increased with temperature increase,and the oxalic acid content increased with the temperature increase at first,maximized at 25℃,and then declined.Two-way ANOVA indicated significant effects of temperature and rice variety on contents of soluble sugar and oxalic acid in rice plants.     

中国粳稻品种春江06的抗白背飞虱机理

与感虫杂交稻汕优63相比较,研究了具有抗性的中国粳稻春江06对白背飞虱的抗性.结果表明,春江06高抗白背飞虱.迁入的白背飞虱拒绝在春江06上着陆,也不能在其上繁殖种群;而白背飞虱更趋向于在汕优63上定居,并繁殖良好.在自由选择的试验条件下,选择春江06的白背飞虱数量显著地低于选择汕优63的.白背飞虱在春江06上平均每天每只雌成虫分泌的蜜露量仅为4.8 mg,而在汕优63上为17.4 mg,表明春江06明显抑制白背飞虱的取食活动.如果让刚羽化的白背飞虱在春江06上连续取食和产卵的话,其产卵能力和卵孵化能力明显降低.白背飞虱在春江06和汕优63上的平均产卵量分别为每只雌成虫42.4个和133.6个,孵化率分别为20.1%和64.5%;在春江06上孵化出的若虫数量只有在汕优63上的10%左右.白背飞虱卵在春江06的水渍状产卵部位有很高的死亡率.在卵孵化之前,水渍状褐变部位迅速形成坏死症状.卵死亡出现在产卵后的1～2 d内.这样的水渍状褐变则极少发生在卵孵化正常的汕优63上.根据以上的发现,可总结出在春江06对白背飞虱的抗性中,抑制取食和杀卵作用是关键的因素.这些作用分别与对迁入白背飞虱的忌避性机理、与居留型白背飞虱产卵能力和卵孵化能力下降的抗生性机理相关.这种品种抗虫性的双抗机理使得粳稻品种春江06具有了稳定和持久的田间抗虫性.     

Projecting Distribution of the Overwintering Population of Sogatella furcifera (Hemiptera: Delphacidae), in Yunnan,China With Analysis on Key Influencing Climatic Factors

Sogatella furcifera (Horváth) is the most threatening migratory rice pest in Yunnan, China. S. furcifera overwinters in low- altitude basins and valleys in southern Yunnan and migrates northward in spring and summer of the following year, causing serious damage during migration. The overwintering distribution, areas, and spatial pattern of S. furcifera are relevant to the migration and outbreak of this pest. Based on a 4-yr field survey (2010–2013), this study projected areas suitable for S. furcifera to overwinter using a species distribution model, and analyzed the key influencing climatic factors using principal component analysis (PCA) and ecological niche factor analysis (ENFA). Our field survey showed that the northern latitudinal- and upper elevation limits of overwintering S. furcifera was 25.4° N and 1,608 m in western Yunnan and 24.2° N and 1,563 m in eastern Yunnan. The species distribution model produced a fragmented distribution pattern, with most of which in western Yunnan and only a few in eastern Yunnan. The PCA and ENFA analyses showed that the mean temperature of the driest quarter and the precipitation of the coldest quarter significantly influenced the distribution of S. furcifera in winter. The results suggested that the complex topography, spatial differences in winter temperatures, and host availability altogether determined the distribution of overwintering S. furcifera . Compared with previous surveys, the northern latitudinal- and upper elevation limits of overwintering S. furcifera were higher, while the population became rarer in some suitable areas due to change of farmland utilization in winter and possibly climate change.     

水稻品种对稻飞虱抗性鉴定方法的比较研究

采用苗期群体筛选、苗期单株鉴定、分蘖盛期单株鉴定、蜜露量测定和若虫发育历期测定5种方法,分别测定了6个新近育成的、不同类型的水稻优质、高产新品种对褐飞虱和白背飞虱的抗性反应。多数品种在苗期接虫鉴定情况下的抗性表现都是一致或十分接近的,而且与品种的类型和抗感性无关。但少数品种随着苗龄的增大,其抗虫性有不同程度的提高。蜜露斑面积测定结果与分蘖盛期接虫鉴定结果基本吻合,初步将蜜露斑面积与抗性级别的关系拟定为：蜜露斑面积［mm2/(雌虫·d)］ 0～100.0≈ 0～3级,100.1～200.0≈5级,>200.1 ≈ 7～9级。综合多项测定指标,认为分蘖盛期接虫鉴定较苗期鉴定更能准确地反映水稻品种成株期的抗性水平;苗期群体筛选和蜜露量测定是水稻抗飞虱的两个快速、便捷、准确的鉴定方法。     

Leersia hexandra, a weed host of the rice brown planthopper, Nilaparvata lugens (Stål)

A population of the rice brown planthopper, Nilaparvata lugens (Stål) (Homoptera: Delphacidae), was abundant on a weed, Leersia hexandra, growing in irrigation canals near rice fields in the Philippines. When individuals of this population were placed on rice, Oryza sativa, feeding was low and they could not survive. Conversely, L. hexandra was not a host for the N. lugens population maintained on rice. Although the two N. lugens populations differed in feeding behaviour, under ‘no choice’ conditions in the greenhouse they interbred and produced progeny which could utilize both L. hexandra and O. sativa as a host. The Leersia population is important in the management of N. lugens on rice as it is attacked by the same predators, parasites and pathogens as the rice population.     

Enhancing the parasitism of insect herbivores through diversification of habitat in Philippine rice fields

The diversification of farming landscapes is proposed as a method to increase farm productivity while at the same time enhancing pest regulation services provided by the natural enemies of insect herbivores. In this study, areas of diversified and conventional rice fields (with 2–14 fields per area?=?0.42–1.31 ha) were established at three sites in the Philippines. The diversified areas had a series (>?40 per hectare) of small (<?2 m²) vegetable patches interspersed along rice bunds (levees). The abundance of planthopper and lepidopteran pests in these areas was monitored during two consecutive cropping seasons using sweep nets with rice yield and damage recorded at the end of each season. Mortality of brown planthopper (Nilaparvata lugens) and yellow stemborer (Scirpophaga incertulas) eggs was monitored through field exposures of infested rice plants. There were no differences in rice yields between the conventional and diversified areas; however, a range of vegetables were produced as a supplementary product from the diversified rice areas. Diversification had no effect on planthopper or leaffolder (Cnaphalocrocis medinalis) abundance at the sites. Adult stemborers (Scirpophaga incertulas) were more abundant in the diversified areas; however, stemborer damage was similar between area treatments in both years. Vegetable patches did not increase parasitism of planthopper eggs; however, egg parasitism was highest close to the vegetable patches, suggesting that egg parasitoids interacted with the patches. Mortality of stemborer eggs was higher in the diversified areas than in the conventional areas. Parasitism due to Trichogramma japonicum and other egg parasitoids was also higher in the diversified areas. These results indicate the potential for vegetable patches to enhance the biological control services provided by egg parasitoids in rice fields; however, the study also indicates a need to carefully select vegetable crops that avoid any potential benefits for rice pests. We discuss the need for further research into diversified farms as a means of achieving sustainable rice production in Asia.