Role of biodiversity in integrated fruit production in eastern North American orchards

• 1 Diversifying agricultural ecosystems to enhance biological control is a promising way of promoting sustainable pest management.
• 2 In the present study, monoculture apple and peach with standard insecticide treatments were compared with three biodiverse treatments (polyculure, monoculture with companion plants and polyculture with companion plants) with reduced standard insecticide use.
• 3 Abundance of insect predators was increased by both the presence of companion plants and extrafloral nectar but parasitism of the leafroller Platynota idaeusalis was not affected.
• 4 There were no consistent effects of biodiversity treatment on either tree growth or fruit yield. Insect injury to Empire apple and peach fruit was not consistently affected by the biodiversity treatments. Granny Smith apples were harvested later than Empire and had more fruit injury in the biodiverse treatments than the standard insecticide control.
• 5 A reduction in pesticides with added biodiversity proved to be a viable alternative to standard chemical insecticide management for temperate tree fruit. Increases in the natural control of pests resulting from increased plant diversity has promise for reducing the reliance on chemical insecticides for pest suppression.

     

Increased temperature induces leaffolder outbreak in rice field

The rice leaffolder, Cnaphalocrosis medinalis Güenée (Lepidoptera: Crambidae), has emerged as a serious pest with significant outbreaks over the last decade in several rice‐growing countries, including China and Bangladesh and resulting in heavy rice yield losses. Climate changes (particularly high temperatures in late winter in Bangladesh) coincide with upsurge in outbreaks of this pest. We generated a statistical model using more than two decades of data to show that increased temperatures associate with this upsurge. Over the 22‐year model period, leaffolder populations in November increased significantly, corresponding to significant monthly temperature trends (but not rainfall) over the same period. Utilizing a linear model, we find that increasing temperature interacts with the amount of rainfall. With the variable month as a proxy for all seasonal effects affecting leaffolder abundance, the model reveals a significant correspondence with climate variations compared to average conditions; specifically, the model predicts that increasing maximum temperatures will lead to more leaffolder, while more rain will decrease their abundance. This study suggests that warmer environment contributed to recent outbreaks of leaffolder in rice‐growing countries; thus, climate change increases rice yield losses by increasing pest population in the field.     

Effectiveness in the field of Bt rice lines against target pests under various cultural regimes

China has a long history of rice cultivation, incorporating several cultural practices known to influence damage by insect pests. Transgenic Bt rice expresses lepidopteran‐specific insecticidal proteins that primarily target lepidopteran insect pests. However, the effectiveness of Bt rice against target insect pests under different cultural regimes has not been evaluated. In this study, the effectiveness of Bt rice lines against rice leaffolder, Cnaphalocrocis medinalis (Guenée) (Lepidoptera: Pyralidae), and striped stem borer, Chilo suppressalis Walker (Lepidoptera: Crambidae), was evaluated under various transplanting densities, crop establishment methods, and planting times. The results showed that Bt rice lines (T2A‐1 and T1C‐19, containing Cry2A and Cry1C, respectively) could prevent damage by these target pests under a range of cultural practices. Injury by C. medinalis or C. suppressalis on rice did not differ with the rice lines under various transplanting densities. Direct‐seeded non‐Bt rice MH63 suffered heavier injury by C. medinalis and C. suppressalis than it did with transplanting, whereas injury to the two Bt rice lines did not differ with planting methods. Planting time significantly affected injury by C. medinalis or C. suppressalis on non‐Bt rice, whereas injury to Bt rice lines did not differ with planting time. These results suggest that transplanting density, planting method, and planting time did not significantly affect the resistance of two Bt rice lines, due to their high insecticidal activity against target insects.     

Experimental field studies on predation and egg parasitism of rice brown planthopper in Indonesia

• 1 Egg parasitism and general predation are known to be important mortality factors in the population dynamics of rice brown planthopper (BPH) Nilaparvata lugens in tropical Asia, but previous studies have not attempted to quantify and compare them.
• 2 Field experiments in Java, Indonesia, are reported for 1993 and 1994. Plants previously infested with BPH eggs were put out in field cage‐enclosures, which, by means of different size mesh gauze covering, allowed either: (1) free access to all natural enemies, (2) access only to egg parasitoids, or (3) no access to any natural enemies.
• 3 After one BPH generation (30 days), numbers of adults and gravid females were counted for each treatment. In addition, plants were dissected to determine the numbers of eggs laid.
• 4 An additional treatment in which all natural enemies were excluded, but lycosid spiders were added, was used in 1994 experiments in an attempt to assess the effects of predators in the absence of egg parasitoids.
• 5 Numbers of BPH adults and eggs laid were highest when natural enemies were excluded and lowest when they had free access. Mortality due to egg parasitoids in the absence of predators was intermediate and significantly different to the two other treatments.
• 6 The effects of added predators in the absence of egg parasitoids gave variable results, but again clearly demonstrated the significance of egg parasitism in overall BPH mortality.
• 7 The conservation of BPH egg parasitoids should form an important element of any rice pest management programme in tropical Asia.

     

Chromosome-level genome assembly of an agricultural pest,the rice leaffolder Cnaphalocrocis exigua (Crambidae,Lepidoptera)

The rice leaffolder Cnaphalocrocis exigua (Crambidae, Lepidoptera) is an important agricultural pest that damages rice crops and other members of related grass families. C. exigua exhibits a very similar morphological phenotype and feeding behaviour to C. medinalis, another species of rice leaffolder whose genome was recently reported. However, genomic information for C. exigua remains extremely limited. Here, we used a hybrid strategy combining different sequencing technologies, including Illumina, PacBio, 10× Genomics, and Hi – C scaffolding, to generate a high-quality chromosome-level genome assembly of C. exigua. We initially obtained a 798.8 Mb assembly with a contig N50 size of 2.9 Mb, and the N50 size was subsequently increased to 25.7 Mb using Hi – C technology to anchor 1413 scaffolds to 32 chromosomes. We detected a total of 97.7% Benchmarking Universal Single-Copy Orthologues (BUSCO) in the genome assembly, which was comprised of ~52% repetitive sequence and annotated 14,922 protein-coding genes. Of note, the Z and W sex chromosomes were assembled and identified. A comparative genomic analysis demonstrated that despite the high synteny observed between the two rice leaffolders, the species have distinct genomic features associated with expansion and contraction of gene families and selection pressure. In summary, our chromosome-level genome assembly and comparative genomic analysis of C. exigua provide novel insights into the evolution and ecology of this rice insect pests and offer useful information for pest control.     

Enhancing rape pollen beetle parasitism within sown flower fields along a landscape complexity gradient

• 1 Sown flower habitats not only are employed in agri‐environment schemes in the European Union to enhance pollinators and birds, such as partridges, but also are hypothesized to contribute to the biological control of pests such as the rape pollen beetle Meligethes aeneus Fabr. by improving habitat and resource availability for its specialized parasitoids.
• 2 In the present study, we selected 20 sown flower fields that included one of the pollen beetles' host plants Sinapis alba L., each centred in a landscape of varying complexity, to test the influence of the surrounding landscape structure on parasitism rate and herbivory by M. aeneus. Additionally, plant cover of S. alba plants within the sown flower fields and numbers of S. alba flowers were also included in the analyses.
• 3 Landscapes with high proportions of semi‐natural habitats supported higher parasitism rates, and sown flower fields with dense S. alba plant cover hosted more parasitoids and suffered from less herbivory.
• 4 We conclude that sown flower fields are not only important for pollinators and birds, but also are long‐term undisturbed, unploughed, insecticide‐free habitats with rich food (nectar/pollen) and host resources for parasitoids, contributing to the build‐up and maintenance of large parasitoid populations, which are important biocontrol agents of rape pollen beetles.

     

Behavioral and physiological responses of rice leaffolder Cnaphalocrocis medinalis to selected wild rices

Of four wild rices evaluated, Oryza perennis and O. punctata showed resistance to rice leaffolder, Cnaphalocrocis medinalis (Guenée), whereas O. australiensis and O. nivara were moderately resistant. C. medinalis larvae showed a strong nonpreference for settling and feeding on Oryza australiensis, O. perennis and O. nivara as compared to susceptible IR36 rice variety. Among wild rices tested, however, only O. australiensis, was more preferred for larval settling and feeding than resistant TKM6 plants. The growth index of C. medinalis on all wild rices, except O. punctata was significantly lower than on IR36 and TKM6 plants. First-instar larvae caged on O. perennis showed significantly lower larval and pupal weights than those on other wild rices. Incorporation of dry leaf powder of O. punctata and O. perennis wild rices in an artificial diet caused high larval mortality. Ovipositing gravid females showed less preference for wild rices than for IR36 and TKM6 plants.Based at the International Rice Research Institute (IRRI), P.O. Box 933, Manila, Philippines     

Effect of Stocked Fish on Rice Leaffolder Cnaphalocrocis medinalis and Rice Caseworm Nymphula depunctalis Populations in Intensive Rice Culture

It is often claimed that fish stocked in rice fields have a significant impact on the rice pest population. However, there is little experimental evidence for this. We used the data of six experiments to find out whether a polyculture of silver barb Barbodes gonionotus (Bleeker), common carp Cyprinus carpio (L.) and Nile tilapia Oreochromis niloticus (L.) has any effect on the population of rice leaffolders Cnaphalocrocis medinalis (Guenée) and rice caseworms Nymphula depunctalis (Guenée), two common pests in intensively cultured rice fields. Fish had no effect on the rice leaffolder population, but significantly lowered the number of rice caseworm adults and larvae. We concluded that fish have some effect on the arthropod pest population in rice fields, although, most probably, only on sluggish pests living in the water or on the water surface.     

Development and characterization of microsatellite markers for rice leaffolder, Cnaphalocrocis medinalis (Guenée) and cross-species amplification in other Pyralididae

Rice leaffolder, Cnaphalocrocis medinalis (Guenée), is a destructive and widespread pest on rice. In this study, 20 microsatellite markers were isolated and characterized from C. medinalis partial genomic libraries using the method of fast isolation by AFLP of sequence containing repeats. Of these markers, 18 markers displayed polymorphisms. Polymorphisms were evaluated in 48 individuals from two natural populations. The number of alleles per locus ranged from 2 to 15, and the expected and observed heterozygosities ranged from 0.324 to 0.934 and from 0.304 to 0.917, respectively. Cross-species amplification was also performed to test the transferability of the 20 microsatellite markers and a moderate level of cross amplication was observed across the three species of Pyralididae (26.67 %). These microsatellite loci would facilitate the future study on population genetics and molecular genetics of rice leaffolder and would also be useful for study in Chilo suppressalis, Scirpophaga incertulas and Pyrausta nubilalis.     

The abundance and diversity of gut bacteria of rice leaffolder Cnaphalocrocis medinalis (Guenée) across life stages

The bacterial community living in the insect gut may play an important role in nutrition, immunity and protection, detoxification of toxins, and inter- and intra-specific communication. Rice leaffolder Cnaphalocrocis medinalis (Guenée) (Lepidoptera: Crambidae) is a notorious pest in rice, and the diversity of the gut bacteria of C. medinalis across life stages are not well understood. Here, the diversity and abundance of the gut bacterial community in C. medinalis through life stages were investigated using Illumina Miseq technology. A total of 22 bacterial phyla, 42 classes, 100 orders, 179 families, 350 genera and 395 species were identified across the different life stages of C. medinalis. Proteobacteria and Firmicutes phyla were the dominant bacterial taxa. Members of the genera Enterococcus, unclassified Enterobacteriaceae, Wolbachia, Acinetobacter, Stenotrophomonas, Microbacterium, Bacillus, Corynebacterium, Lampropedia, and Sphingobacterium were found at all life stages. Enterococcus and unclassified Enterobacteriaceae occupied higher relative abundance among bacteria community in the 2nd to 5th instar larvae, pupae and adults. The structure of bacterial community differed across the life stages of C. medinalis. Our findings will enrich the understanding of gut bacteria in C. medinalis, and will provide foundation and assistance for the development of novel pest management strategies through utilization of microbiota.     

控制大田和自然大田稻纵卷叶螟危害水稻生理生态参数估算模型

为了准确监测和客观评估稻纵卷叶螟对水稻生长发育和产量形成的危害,利用ASD Field Spec3地物波谱仪和SPAD-502叶绿素仪分别采集控制大田试验（2015年和2019年）和自然大田试验（2020年）在各生育期（拔节期、孕穗期、灌浆期、成熟期）水稻的冠层高光谱数据和SPAD值,调查采集样点的虫量和水稻卷叶率,对比分析两种试验中稻纵卷叶螟的虫害发生特征、水稻冠层光谱特征和水稻生理生态参数特征,建立基于高光谱参数的水稻受稻纵卷叶螟危害的生理生态参数估算模型。结果表明,（1）两种试验的水稻SPAD值和冠层的红边至近红外波段的反射率均随着稻纵卷叶螟虫害程度的加重而降低,而可见光波段的反射率则相反;（2）自然大田试验的SPAD值和红光至近红外波段的冠层反射率在水稻生长发育前期要显著低于控制大田试验,而到了后期则反而要略高于控制大田试验;（3）综合分析筛选出自然大田试验和控制大田试验中的多个虫害特征参数和植被指数分别构建出了SPAD的单因子和多因子估算模型,各模型均达到了较好的估算效果,在单因子模型中EVI的二项式函数模拟效果最好,而多因子线性回归估测模型的模拟效果优于所有的单因子模型;（4）通过2021年对这些模型的应用检验发现：这些模型中基于虫量、卷叶率、OSAVI、EVI和DVI的单因子估算模型的SPAD估算值与实测值拟合度很高,其R_v²均超过了0.8,达到了比较理想的估算效果,这为稻纵卷叶螟危害下的水稻SPAD值估测提供了一种精度较高且可行的估算方法。     

The usefulness of destructive host feeding parasitoids in classical biological control: theory and observation conflict

Abstract.

• 1 We examine the conventional wisdom among biological control practitioners that destructive host feeding is a desirable attribute in parasitoids employed for classical biological control, using both the predictions of population dynamics theory and historical data on biological control introductions of Hymenoptera against Homoptera.
• 2 Population dynamics theory predicts that destructive host feeders, compared with other parasitoids, are (a) either just as likely or more likely to become established, and (b) unable to depress host equilibria as strongly.
• 3 Analyses of the B IOC AT database suggest that among parasitoids of Homoptera destructive host feeders are superior to other parasitoids with respect to both establishment rate and success rate.
• 4 We present likely explanations for the disparity between the predictions of population dynamics theory and the results of database analysis. A partial explanation for the mismatch between theory and observation with respect to the degree of pest suppression may be that females of destructive host feeding parasitoids rely less upon hosts as a food source when alternative foods such as honeydew and nectar are plentiful.
• 5 We conclude that, despite the predictions of population dynamics theory, destructive host feeders are probably better biological control agents than other parasitoids, and certainly no worse, but that it would imprudent to use destructive host feeding as the sole, or even primary, selection criterion when seeking agents for classical biological control.

     

Targeted sugar provision promotes parasitism of the cereal leaf beetle Oulema melanopus

• 1 Parasitoids may often lack access to sugar (e.g. floral nectar) in agricultural settings. Strategically timed spraying of host plants with sugar solution may provide one means of enhancing parasitism at the same time as minimizing nontarget effects (e.g. benefiting the pest itself).
• 2 Sucrose was sprayed in wheat fields of northern Utah (U.S.A.) to assess the effects on parasitism of the cereal leaf beetle Oulema melanopus by the larval parasitoid Tetrastichus julis.
• 3 Early‐season sugar provisioning, when larvae of the pest were first hatching and parasitoid adults were newly emerged, did not affect the numbers of cereal leaf beetle larvae that matured in treated plots but increased parasitism rates of beetle larvae by four‐fold in 2006 and by seven‐fold in 2007.
• 4 No net influx of adult parasitoids into plots was detected after the application of sugar. Locally‐emerging parasitoids may have spent less time searching for their own food needs versus hosts. A laboratory experiment also confirmed that access to sucrose significantly increased parasitoid longevity.
• 5 The field experimental results obtained demonstrate that applications of sugar, implemented to target a key time of the growing season when benefits are maximized for parasitoids and minimized for their hosts, can strongly promote parasitism of the cereal leaf beetle in wheat fields.

     

Disruptive Sublethal Effects of Insecticides on Biological Control: Altered Foraging Ability and Life Span of a Parasitoid after Feeding on Extrafloral Nectar of Cotton Treated with Systemic Insecticides

Predictions in integrated pest management on the compatibility of an insecticide with biological control often are based on incomplete screening tests. While measuring levels of mortality from direct insecticide exposure is a very common screening method, possible sublethal effects as a result of either direct or indirect insecticide exposure remain relatively unknown. The impact of sublethal effects on the success of biological control can be as deleterious as mortality. Here, we report the reduced host foraging ability and longevity of the parasitoid Microplitis croceipes Cresson (Hymenoptera: Braconidae) after feeding on extrafloral nectar from cotton (Gossypium hirsutum L., Malvaceae) plants that were treated with systemic insecticides. The insecticides used in this study are regularly applied in cotton-growing areas in the United States. For all tested insecticides, longevity of M. croceipes females that fed on nectar from cotton was affected for at least 10 days after plants were treated with insecticides. Moreover, the parasitoid's host foraging ability was severely affected for periods ranging from 2 days (imidacloprid) to 18 days (aldicarb) after insecticide application. The consequences of these sublethal effects on the success of biological control are discussed.     

Basic components of the program of ecological integrated management of lepidopterous rice pests (Lepidoptera,Pyralidae) in the Red River Delta in North Vietnam: V. General manual

A general technological scheme of integrated ecological management of lepidopterous rice pests is proposed. The suggested algorithm comprises the following principal elements: (1) two-level economic threshold of damage (TETD) for the rice leaffolder (Chaphalocrocis medinalis); (2) TETD for the yellow stemborer (Scirpophaga incertulas); (3) monitoring of the population dynamics of lepidopterous pests and their natural enemies; (4) decision-making based on standard sampling procedures; (5) the level of entomophage efficiency, characterizing ecological stability of the paddy agroecosystem, which can be used to correct the TETD values; (6) the apparatus and tactics of lepidopterous pest population management.     

Nectar exploitation by herbivores and their parasitoids is a function of flower species and relative humidity

In conservation biological control, diversification of the agro ecosystem with flowering vegetation is seen as an important tool to support the broad range of predators and parasitoids that require nectar and pollen sources to survive and reproduce. In order to identify flowering plants that provide suitable food sources for natural enemies without supporting the pest species, we analyzed the exploitation of 19 flowering plants by two important lepidopteran cabbage pests, Pieris rapae and Plutella xylostella, and their hymenopteran parasitoids, Cotesia glomerata and Diadegma semiclausum. The experiments were conducted at 90% r.h., while Pieris rapae was tested both at 45% r.h. and at 90% r.h. At 45 ± 5% r.h., corresponding with field conditions at which P. rapae is predominantly active, the butterfly was unable to feed on a number of exposed floral nectar sources whose nectar was successfully exploited at 90% r.h. The broader nectar exploitation by P. rapae at the high humidity is presumably explained by the resulting decrease in nectar viscosity. When comparing D. semiclausum and its herbivorous host P. xylostella, the herbivore exploited a broader range of plants. However, those plants that benefited both the parasitoid and the herbivore had a much stronger effect on the longevity of the parasitoid. The results from the accessibility bioassay suggest that flowers where nectar is not accessible can have a negative impact on insect survival presumably by stimulating foraging without providing accessible nectar. Our results underline the importance of considering species-specific environmental conditions when fine-tuning the choice of nectar sources to be used in conservation biological control programs.     

稻纵卷叶螟绒茧蜂对寄主的搜索行为

稻纵卷叶螟绒茧蜂是稻纵卷叶螟幼虫的重要天敌。以Y形嗅觉仪测定了稻纵卷叶螟2—3龄幼虫虫粪、4—5龄幼虫虫粪、健康水稻、稻纵卷叶螟幼虫为害后水稻在纵卷叶螟绒茧蜂对寄主的搜索过程中的作用。结果表明已交配的雌蜂显著趋向稻纵卷叶螟2—3龄幼虫虫粪和4—5龄幼虫虫粪,不趋向健康水稻、稻纵卷叶螟幼虫为害后的水稻。雄蜂、处女雌蜂不显著趋向健康水稻、稻纵卷叶螟幼虫为害后水稻、稻纵卷叶螟2—3龄幼虫虫粪、稻纵卷叶螟4—5龄幼虫虫粪。利用固相微萃取(SPME)及气相色谱/质谱(GC/MS)联用分析稻纵卷叶螟2—3龄幼虫虫粪的化学成分,并通过Y-形嗅觉仪测试已交配雌蜂对稻纵卷叶螟2—3龄幼虫虫粪化学成分标准品的嗅觉反应,结果表明已交配的雌蜂显著趋向1-十一烯和异缬草醛,稻纵卷叶螟幼虫虫粪中的1-十一烯和异缬草醛可能是稻纵卷叶螟绒茧蜂搜索寄主的利他素。     

PHYSIOLOGICAL EFECTS OF PAICHONGDING APPLIED TO RICE ON THE Nilaparvata lugens (STÅ L), THE BROWN PLANTHOPPER

Nilaparvata lugens (Stål) is a major rice pest in Asia. Paichongding is a novel neonicotinoid insecticide developed in 2008. The effects of this insecticide on the activity of detoxification enzymes of N. lugens and on rice resistance to the pest were examined in the laboratory. The results showed that paichongding could significantly decrease the acetylcholinesterase and GSHs transferase activities of N. lugens. The variation tendency of mixed function oxidase (MFO) activity was similar with that of the esterase. After 12 h treatment, there was no significance between the treatment and control. However, the activities of MFO and esterase increased after 24 and 48 h treatment, which suggested that MFO and esterase may play an important role in the detoxification of paichongding for N. lugens. Our results also demonstrated that treated with paichongding, damage levels of rice plants were significantly lower than those of control plants except 15 days after treatment. Compared with the control, injury indices decreased 70.22, 49.12, 34.44, and 23.23% at 3 , 6 , 9, and 12 days after paichongding treatment, respectively. The laboratory results suggested that paichongding may be effective for the control of brown planthopper.     

Development of leaffolder resistant transgenic rice expressing <Emphasis Type="Italic">cry2AX1</Emphasis> gene driven by green tissue-specific <Emphasis Type="Italic">rbcS</Emphasis> promoter

The insecticidal cry genes of Bacillus thuringiensis (Bt) have been successfully used for development of insect resistant transgenic rice plants. In this study, a novel cry2AX1 gene consisting a sequence of cry2Aa and cry2Ac gene driven by rice rbcS promoter was introduced into a rice cultivar, ASD16. Among 27 putative rice transformants, 20 plants were found to be positive for cry2AX1 gene. The expression of Cry2AX1 protein in transgenic rice plants ranged from 5.95 to 122.40 ng/g of fresh leaf tissue. Stable integration of the transgene was confirmed in putative transformants of rice by Southern blot hybridization analysis. Insect bioassay on T₀ transgenic rice plants against rice leaffolder (Cnaphalocrosis medinalis) recorded larval mortality up to 83.33 %. Stable inheritance and expression of cry2AX1 gene in T₁ progenies was demonstrated using Southern and ELISA. The detached leaf bit bioassay with selected T₁ plants showed 83.33–90.00 % mortality against C. medinalis. The whole plant bioassay for T₁ plants with rice leaffolder showed significant level of resistance even at a lower level of Cry2AX1 expression varying from 131 to 158 ng/g fresh leaf tissue during tillering stage.