Bt Rice Expressing Cry2Aa Does Not Harm Cyrtorhinus lividipennis,a Main Predator of the Nontarget Herbivore Nilapavarta lugens

T2A-1 is a newly developed transgenic rice that expresses a synthesized cry2Aa gene driven by the maize ubiquitin promoter. T2A-1 exhibits high resistance against lepidopteran pests of rice. The brown planthopper, Nilapavarta lugens (Stål), is a main nontarget sap-sucking insect pest of rice, and Cyrtorhinus lividipennis (Reuter) is the major predator of the eggs and young nymphs of planthoppers. As C. lividipennis may expose to the Cry2Aa protein via N. lugens, it is therefore essential to assess the potential effects of transgenic cry2Aa rice on this predator. In the present study, three experiments were conducted to evaluate the ecological risk of transgenic cry2Aa rice to C. lividipennis: (1) a direct feeding experiment in which C. lividipennis was fed an artificial diet containing Cry2Aa at the dose of 10-time higher than that it may encounter in the realistic field condition; (2) a tritrophic experiment in which the Cry2Aa protein was delivered to C. lividipennis indirectly through prey eggs or nymphs; (3) a realistic field experiment in which the population dynamics of C. lividipennis were investigated using vacuum-suction. Both direct exposure to elevated doses of the Cry2Aa protein and prey-mediated exposure to realistic doses of the protein did not result in significant detrimental effects on the development, survival, female ratio and body weight of C. lividipennis. No significant differences in population density and population dynamics were observed between C. lividipennis in transgenic cry2Aa and nontransgenic rice fields. It may be concluded that transgenic cry2Aa rice had no detrimental effects on C. lividipennis. This study represents the first report of an assessment continuum for the effects of transgenic cry2Aa rice on C. lividipennis.     

Role of different habitats for the functional response of Crytorrhinus lividipennis (Hemiptera: Miridae) on Nilaparvata lugens (Hemiptera: Delphacidae)

The functional response of a predator, Cyrtorrhinus lividipennis, on the brown planthopper, Nilaparvata lugens, was investigated in two different experimental habitats: a piece of tiller in a petri dish (5.5?cm in diameter) and a rice plant in a net cage (5.5?cm diameter?×?43?cm height) for 24?h at room temperature. In the petri dish experiment, 2nd–5th instar nymphs, adult male, and female C. lividipennis were introduced in separate experiments to eggs of N. lugens at densities of five, 10, 20, 30, and 40 eggs per piece of rice. In the rice plant experiment, each C. lividipennis was introduced to a cage with a rice plant containing N. lugens eggs. After 24?h, the number of dead eggs and remaining eggs were counted and data fitted to three functional response models. Among the three types of functional responses, Type II best described the predator response to host densities in N. lugens in both experimental habitats, according to the logistic regression analysis value. The results showed that C. lividipennis was a more effective predator in the rice plant experiment compared to the disc experiment. Additionally, the searching efficiency and handling time parameters were different in the two different experimental habitats. This may cause errors when applying the functional response to biological control and predator–prey models. Different habitats and other environmental conditions from the experiment and natural rice field have to be considered.     

Early season natural control of the brown planthopper, Nilaparvata lugens: the contribution and interaction of two spider species and a predatory bug

Nilaparvata lugens St?l, the Brown Planthopper (BPH), is a major pest in rice. The lycosid Pardosa pseudoannulata (B?senberg & Strand) and the linyphiid Atypena formosana (Oi) are the early dominant predators in irrigated rice. Later, predatory bugs, including the mirid Cyrtorhinus lividipennis Reuter, become dominant. In unsprayed rice, BPH numbers normally remain low. While P. pseudoannulata is known to be a key natural enemy of BPH, the contribution to BPH reduction by the smaller A. formosana is less well known. Due to the size difference, A. formosana may also be an intraguild prey of P. pseudoannulata. To investigate predation on BPH by the two spider species alone, together and in combination with C. lividipennis, two cage experiments were conducted, the first with adult spiders, the second with immature/unmated spiders. In the latter, spiders were introduced with a delay to allow a better establishment of C. lividipennis. In both experiments, BPH numbers were lowest in treatments with more than one predator species present. Intermediate BPH reduction was obtained with P. pseudoannulata followed by A. formosana and C. lividipennis. While P. pseudoannulata can prey upon large nymphs and adult BPH, A. formosana favour early instar BPH, leading to a more even control across instars in treatments with both spider species. Pardosa pseudoannulata numbers increased more with A. formosana or A. formosana and C. lividipennis present. In contrast, P. pseudoannulata reduced A. formosana and C. lividipennis numbers. The presence of C. lividipennis apparently lessened intraguild predation on A. formosana and may be an intraguild prey of A. formosana. Competition for prey may have added to the antagonistic interactions found. From a biological control perspective, the presence of both spiders in early rice is an advantage for the biological control of BPH in rice. In early rice, results show that A. formosana is an important predator of BPH and, like C. lividipennis, can complement control by P. pseudoannulata and serve as intraguild prey for the latter species.     

Behavioral response of Nilaparvata lugens (Stål), Cyrtorhinus lividipennis Reuter and Paederus fuscipes Curtis to three synthetic volatile chemical compounds

Plant essential oils (EOs) and a wide range of chemicals affect insect pests in many ways, such as via stimulatory, deterrent, toxic and hormonal effects. Three different compounds ((E)-β-caryophyllene (E-β-C), D-limonene (D-lime) and trans-2-dodecenol (T-2-D)) were tested against Nilaparvata lugens, Cyrtorhinus lividipennis and Paederus fuscipes, and their behavioral response was assessed. The results showed that on average, more N. lugens nymphs were repelled by E-β-C and T-2-D than by D-lime. More C. lividipennis nymphs were attracted to T-2-D and D-lime than to E-β-C. However, P. fuscipes displayed no significant response to the three chemical compounds. The results also demonstrated that T-2-D has exerted significant repellency against N. lugens and a significant attraction for C. lividipennis, while E-β-C and D-lime have no significant effect on any tested insect. T-2-D was selected and tested in a greenhouse under semi-field conditions, where the observations confirmed the results of the laboratory experiments. From the results, it can be concluded that T-2-D at a concentration of 0.06 g/L is an effective synthetic volatile chemical compound and is the strongest repellent of N. lugens and the strongest attractant for C. lividipennis. This synthetic chemical compound can be used as a pest management tool in rice agroecosystems.     

Laboratory screening supports the selection of sesame (Sesamum indicum) to enhance Anagrus spp. parasitoids (Hymenoptera: Mymaridae) of rice planthoppers

Planthopper (Delphacidae) pests have broken out frequently in Asia over the last decade leading to interest in enhancing the impact of natural enemies by growing nectar plants on the bunds that border rice fields. Such targeted use of plant diversity is popular in other crop systems but there is a marked lack of information on the scope for its use in rice, particularly the important aspect of which plant species to use. This study used Y-tube olfactometer assays to measure the response of two important parasitoids of delphacid pests to candidate nectar plants. Anagrus optabilis exhibited significant attraction to the air from six of the seven plant species whilst Anagrus nilaparvatae appeared more selective, exhibiting attraction to only seven of the 23 plants screened and repulsion to one. Sesamum indicum, Emilia sonchifolia, and Impatiens balsamena were the only three plants attractive to both parasitoids. Laboratory longevity of adult female A. nilaparvatae and A. optabilis with access to sesame flowers was significantly greater than with access to sesame from which the flowers were removed plus water. Similarly, both parasitoids parasitized significantly more brown planthopper (Nilaparvatae lugens) eggs in the presence of sesame flowers. Handling time of A. nilaparvatae was reduced from 31.29 to 18.36 min by access to sesame nectar. Findings show that sesame has a marked beneficial effect on key parameters of Anagrus spp. and justifies further evaluation of its utility as a nectar plant to improve biological control in Asian rice systems.     

Prey preference of the wolf spider,Pardosa pseudoannulata (Boesenberg et Strand)

Functional responses of the wolf spider, Pardosa pseudoannulata (Boesenberg et Strand) attacking the rice brown planthopper, Nilaparvata lugens (Stål.), and the mirid predator Cyrtorhinus lividipennis Reuter were both those of Holling Type II. The attack rate was higher and handling time lower for C. lividipennis. However, when caged with the two prey, the wolf spider showed a significant preference for N. lugens at a lower prey proportion. Proportions of prey attacked were significantly different from the expected ratios of prey available as well as from the predicted preferences derived from the functional response parameters. As proportions of N. lugens attacked changed from greater to less than expected as the proportions of N. lugens available increased, a “reverse switch” behaviour seems to be evident.     

稻田氮肥施用量对黑肩绿盲蝽捕食功能的影响

在实验室条件下研究了黑肩绿盲蝽Cyrtorhinuslividipennis Reuter在不同含氮量稻株上对褐飞虱Nilaparvata lugens Stal卵和低龄若虫的捕食能力、对褐飞虱卵的捕食功能反应以及褐飞虱蜜露和水稻伤流液对其捕食 能力的影响。结果表明,黑肩绿盲蝽对褐飞虱卵和若虫的捕食量均与寄主植物的含氮量呈显著 负相关。黑肩绿盲蝽在相同氮肥施用量的稻株上连续饲养2代后对褐飞虱卵的捕食能力没有改变 。黑肩绿盲蝽对褐飞虱卵的功能反应呈Holling Ⅱ型方程,其参数瞬时发现率(a)和处置时间(T_h)只与寄主含氮量有关,而与黑肩绿盲蝽种群和褐飞虱卵的来源无关。 在高氮量稻株上黑肩绿盲蝽种群对褐飞虱卵的瞬时发现率(a)下降导致了功能反应的减弱, 而在相同含氮量稻株上黑肩绿盲蝽种群之间的捕食功能没有明显差异。黑肩绿盲蝽成虫取食水 稻伤流液和褐飞虱蜜露时寿命明显延长,取食高氮稻株的褐飞虱分泌的蜜露对延长黑肩绿盲蝽 雌成虫寿命的作用最大。但是,在高氮稻株上褐飞虱蜜露显著降低黑肩绿盲蝽的捕食能力。这 些结果表明黑肩绿盲蝽对褐飞虱自然控制作用的下降是稻田过量施用氮肥后褐飞虱种群增加的 主要原因之一。     

Reciprocal intraguild predation between two mirid predators,Cyrtorhinus lividipennis and Tytthus chinensis (Hemiptera: Miridae)

Interactions between predator species shape ecological communities and are crucial in the relationship between biodiversity and ecosystem functioning. They contribute to improving the natural biological control. Cyrtorhinus lividipennis Reuter and Tytthus chinensis Stål (Hemiptera: Miridae) are important natural enemies of brown planthopper, Nilaparvata lugens Stål (Hemiptera: Delphacidae), the most destructive rice pest in Asia. Comparative functional responses of both sexes of the two mirids at different development stages were estimated and the direction, symmetry, as well as intensity of intraguild predation (IGP) were studied in the laboratory. Prey preferences of the two mirid species and the influence of alternative prey on functional responses were also evaluated. The mirids exhibited reciprocal IGP in addition to consuming eggs of BPH. All predator–prey combinations exhibited a type II functional response. Females and fourth instar nymphs of C. lividipennis showed greater voracity for eggs of BPH than of T. chinensis. The two mirids were more voracious to intraguild prey than to extraguild prey. Alternative prey released the functional responses of C. lividipennis to both intra- and extraguild prey. In contrast, alternative prey had no effect on the functional response of T. chinensis. RIGP was symmetrical in the absence of extraguild prey. And in the presence of extraguild prey that was common in the field, resulted in different responses by the mirids.     

Host Status of Crotalaria juncea,Sesamum indicum,Dolichos lablab,and Elymus glaucus to Meloidogyne javanica

Reproduction of Meloidogyne javanica on Crotalaria juncea PI 207657 and cv. Tropic Sun, Sesamum indicum, Dolichos lablab, and Elymus glaucus was assessed using a root-gall index, a reproductive index obtained by dividing the final population of juveniles (J2) in soil by the initial J2 population (Pf/Pi), and the number of J2 per gram of root recovered from roots by mist chamber extraction. Lycopersicon esculentum (cv. UC 204 C) was included as a susceptible host. The root-gall index and soil reproductive index were poor indicators of the host status of our test plants as compared with mist chamber extraction of J2 from roots. Lycopersicon esculentum had a mean root-gall index of 7.8. Some plants of S. indicum and E. glaucus had a few galls and other plants had none, with mean root-gall indices of 1.6 and 0.8, respectively. No galls were observed in C. juncea and D. lablab. Lycopersicon esculentum had the highest mean soil Pf/Pi value (mean = 1.93), while in C. juncea and some replicates of S. indicum no soil J2 were found. Even though some replicates had no galls, all replicates supported nematode reproduction. The mean numbers of J2 per gram root after 5 days of mist extraction were 447.7, 223.3, 165.5, 96.9, 42.3, and 41.9 for D. lablab, L. esculentum, E. glaucus, S. indicum, and C. juncea PI 207657 and cv. Tropic Sun, respectively. Accurate assessment of nematode resistance was influenced by sampling time and the nematode extraction technique used. Individual plants of both C. juncea and S. indicum supported nematode reproduction to some extent; however, both C. juncea and S. indicum have potential as cover crops to reduce M. javanica numbers.     

Juvenile hormone-mediated reproduction induced by a sublethal concentration of imidacloprid in Cyrtorhinus lividipennis (Hemiptera: Miridae)

The Hemipteran predator, Cyrtorhinus lividipennis, feeds on the eggs and nymphs of rice planthoppers and leafhoppers. We previously demonstrated that sublethal concentrations of imidacloprid stimulated the reproduction of C. lividipennis. Considering the essential roles of juvenile hormone (JH) in insect reproduction, we speculated that sublethal concentrations of imidacloprid may stimulate the reproduction of C. lividipennis by regulating JH level. To test this, we cloned C. lividipennis JH acid methyl transferase (ClJHAMT) and JH esterase (ClJHE), which are responsible for JH biosynthesis and degradation genes, respectively. We then knocked down ClJHAMT by injecting dsRNA into C. lividipennis nymphs and found that emerging female adults exhibited 88.8% lower expression of the vitellogenin gene (ClVg) and the number of eggs was reduced by 41.5% as compared with controls. Silencing ClJHE increased ClVg mRNA expression by 275.0% but did not affect fecundity. A sublethal concentration of imidacloprid (LC₂₀) increased the JH titer in females by 35.3% and 60.6% at 24 and 48 h post-emergence, respectively. In treatments containing both imidacloprid and dsJHAMT, the silencing of CLJHAMT reduced the number of eggs produced by adult females by 21.4% as compared to the control (imidacloprid + dsGFP). Our results indicated that sublethal concentration of imidacloprid may induce C. lividipennis reproduction by upregulating JH level via JHAMT. The finding could provide valuable information for improved integration of C. lividipennis and insecticides in pest management.     

Functional Invertebrate Prey Groups Reflect Dietary Responses to Phenology and Farming Activity and Pest Control Services in Three Sympatric Species of Aerially Foraging Insectivorous Birds

Farming activity severely impacts the invertebrate food resources of farmland birds, with direct mortality to populations of above-ground arthropods thorough mechanical damage during crop harvests. In this study we assessed the effects of phenological periods, including the timing of harvest, on the composition and biomass of prey consumed by three species of aerial insectivorous birds. Common Swifts Apus apus, Barn Swallows Hirundo rustica and House Martins Delichon urbica breed sympatrically and most of their diet is obtained from agricultural sources of invertebrate prey, especially from oil-seed rape crops. We categorized invertebrate prey into six functional groups, including oil-seed rape pests; pests of other arable crops; other crop-provisioned taxa; coprophilous taxa; and taxa living in non-crop and mixed crop/non-crop habitats. Seasonality impacted functional groups differently, but the general direction of change (increase/decrease) of all groups was consistent as indexed by prey composition of the three aerial insectivores studied here. After the oil-seed rape crop harvest (mid July), all three species exhibited a dietary shift from oil-seed rape insect pests to other aerial invertebrate prey groups. However, Common Switfts also consumed a relative large quantity of oil-seed rape insect pests in the late summer (August), suggesting that they could reduce pest insect emigration beyond the host plant/crop. Since these aerially foraging insectivorous birds operate in specific conditions and feed on specific pest resources unavailable to foliage/ground foraging avian predators, our results suggest that in some crops like oil-seed rape cultivations, the potential integration of the insectivory of aerial foraging birds into pest management schemes might provide economic benefits. We advise further research into the origin of airborne insects and the role of aerial insectivores as agents of the biological control of crop insect pests, especially the determination of depredation rates and the cascading effects of insectivory on crop damage and yield.     

黑肩绿盲蝽耐饥饿能力的研究

【目的】为早期释放黑肩绿盲蝽Cyrtorhinus lividipennis提供理论依据,研究了黑肩绿盲蝽不同虫态耐受饥饿及低温的能力。【方法】室内条件下,比较了稻苗+水、无苗有水和无苗无水三种食物条件下黑肩绿盲蝽耐饥力大小。【结果】适温(26℃)下,黑肩绿盲蝽3龄若虫、5龄若虫和成虫在稻苗+水的存活时间显著高于无苗有水,无苗有水时的存活时间又显著高于无苗无水,表明稻苗对于黑肩绿盲蝽有营养作用,取食稻苗有助于提高黑肩绿盲蝽的耐饥力。黑肩绿盲蝽成虫耐饥力最强,3龄若虫和5龄若虫接近,有苗有水时,3龄若虫、5龄若虫和成虫的平均存活时间分别为2.10、2.22和4.25 d。在低温(15℃)下,水稻苗对黑肩绿盲蝽成虫的存活不利,有苗有水时雌雄成虫的存活时间均低于无苗有水处理,其中雌成虫两处理间的差异显著(P=0.001)。【结论】黑肩绿盲蝽对饥饿和低温有较强的耐受性,以成虫最强,水稻生长前期田间释放时以成虫为宜。     

转Cry1Ab和Cry1Ac融合基因型抗虫水稻对田间二化螟和大螟种群发生动态的影响

以Bt水稻华恢1号(Cry1Ac和CryAb融合基因;简称HH1)及其对照亲本明恢63(简称MH63)稻田靶标害虫二化螟Chilosuppressalis和次靶标害虫大螟Sesamia inferens为研究对象,研究了转基因抗虫水稻大田螟虫发生规律及其靶标和次靶标害虫致害力差异。结果表明,Bt水稻及其对照亲本上二化螟或大螟的卵块数量差异不显著,同时,对照亲本上二化螟与大螟的落卵量差异不显著,但Bt水稻上二化螟的落卵量显著大于大螟。与对照亲本相比,Bt水稻上二化螟幼虫发生量显著降低,降幅高达84.9%—100%,但大螟发生量差异不显著;此外,对照亲本上二化螟幼虫发生量显著高于大螟,但Bt水稻上两者差异不显著。同时,Bt水稻上二化螟导致的枯心/白穗率和受害丛率都显著低于其在对照亲本上的致害程度,降幅分别为30.8%—98.3%和11.4%—96.6%,而大螟差异不显著。可见,Bt水稻对靶标害虫二化螟具有较高抗性,而对次靶标害虫大螟的抗性不明显。另一方面,Bt水稻和对照亲本上二化螟导致的枯心/白穗率和受害从率都显著高于大螟。可见,二化螟仍是当前非转基因水稻上的主要害虫,而Bt水稻对二化螟幼虫发生的显著抑制作用以及对大螟幼虫发生的不显著影响,使得其大面积商业化种植下靶标害虫二化螟和次靶标害虫大螟间的竞争替代成为可能。     

Cover Cropping Alters the Diet of Arthropods in a Banana Plantation: A Metabarcoding Approach

Plant diversification using cover crops may promote natural regulation of agricultural pests by supporting alternative prey that enable the increase of arthropod predator densities. However, the changes in the specific composition of predator diet induced by cover cropping are poorly understood. Here, we hypothesized that the cover crop can significantly alter the diet of predators in agroecosystems. The cover crop Brachiaria decumbens is increasingly used in banana plantations to control weeds and improve physical soil properties. In this paper, we used a DNA metabarcoding approach for the molecular analysis of the gut contents of predators (based on mini-COI) to identify 1) the DNA sequences of their prey, 2) the predators of Cosmopolites sordidus (a major pest of banana crops), and 3) the difference in the specific composition of predator diets between a bare soil plot (BSP) and a cover cropped plot (CCP) in a banana plantation. The earwig Euborellia caraibea, the carpenter ant Camponotus sexguttatus, and the fire ant Solenopsis geminata were found to contain C. sordidus DNA at frequencies ranging from 1 to 7%. While the frequencies of predators positive for C. sordidus DNA did not significantly differ between BSP and CCP, the frequency at which E. caraibea was positive for Diptera was 26% in BSP and 80% in CCP; the frequency at which C. sexguttatus was positive for Jalysus spinosus was 14% in BSP and 0% in CCP; and the frequency at which S. geminata was positive for Polytus mellerborgi was 21% in BSP and 3% in CCP. E. caraibea, C. sexguttatus and S. geminata were identified as possible biological agents for the regulation of C. sordidus. The detection of the diet changes of these predators when a cover crop is planted indicates the possible negative effects on pest regulation if predators switch to forage on alternative prey.     

Penetration of Crotalaria juncea,Dolichos lablab,and Sesamum indicum Roots by Meloidogyne javanica

Penetration of Crotalaria juncea (PI 207657 and cv. Tropic Sun) Dolichos lablab cv. Highworth, and Sesamum indicum by juveniles (J2) of Meloidogyne javanica was assessed to investigate the mechanism by which these plants may reduce nematode numbers in the field. Growth chamber experiments were conducted at 25 C, with vials containing 90 g sand infested with 450 J2; tomato (UC 204 C) was included as a susceptible host. Fifteen days after inoculation, roots were stained and the nematodes within stained roots were counted. Both C. juncea lines were highly resistant to penetration, as they contained significantly fewer nematodes per cm of root and per root system than the other plants. Although containing more nematodes per cm of root than C. juncea, S. indicum and D. lablab had significantly fewer nematodes per root system and per cm of root than tomato. Roots were significantly longer in the plants with the lowest nematode penetration. Although C. juncea, D. lablab, and S. indicum may have potential utility as cover or rotation crops in soil infested with M. javanica, further quantitative information on the reproduction of M. javanica and other nematodes in these plants is needed.     

稻田穗期主要捕食性天敌对两种盲蝽集团内捕食的初步研究

【目的】集团内捕食是影响农业系统广食性天敌对靶标害虫控制作用的重要因素,全面揭示稻田广食性天敌对稻飞虱重要天敌黑肩绿盲蝽Cyrtorhinus lividipennis Reuter和中华淡翅盲蝽Tytthus chinensis(St?l)(半翅目:盲蝽科)的集团内捕食作用有助于更好地保护利用天敌。【方法】建立以两种盲蝽为猎物对象的种特异性二重定量PCR系统,检测比较不同抗性品种穗期田间主要捕食者对两种盲蝽的集团内捕食作用。【结果】(1)本研究建立的二重定量PCR具有的物种专化性,两种检测靶标灵敏度高且相似,可用于田间捕食者猎物分析;(2)感虫水稻品种上捕食者对盲蝽的捕食强度高于抗性水稻品种;不同种类捕食者对盲蝽的集团内捕食强度有显著差异;捕食者对黑肩绿盲蝽集团内捕食强度显著高于中华淡翅盲蝽。【结论】捕食性盲蝽在稻田生态系统遭遇集团内捕食,其集团内捕食强度与水稻品种抗性、捕食者种类和猎物丰富度有关。     

Crop rotation and residue management effects on carbon sequestration,nitrogen cycling and productivity of irrigated rice systems

The effects of soil aeration, N fertilizer, and crop residue management on crop performance, soil N supply, organic carbon (C) and nitrogen (N) content were evaluated in two annual double-crop systems for a 2-year period (1994–1995). In the maize-rice (M-R) rotation, maize (Zea mays, L.) was grown in aerated soil in the dry season (DS) followed by rice (Oriza sativa, L.) grown in flooded soil in the wet season (WS). In the continuous rice system (R-R), rice was grown in flooded soil in both the DS and WS. Subplot treatments within cropping-system main plots were N fertilizer rates, including a control without applied N. In the second year, sub-subplot treatments with early or late crop residue incorporation were initiated after the 1995 DS maize or rice crop. Soil N supply and plant N uptake of 1995 WS rice were sensitive to the timing of residue incorporation. Early residue corporation improved the congruence between soil N supply and crop demand although the size of this effect was influenced by the amount and quality of incorporated residue. Grain yields were 13-20% greater with early compared to late residue incorporation in R-R treatments without applied N or with moderate rates of applied N. Although substitution of maize for rice in the DS greatly reduced the amount of time soils remained submerged, the direct effects of crop rotation on plant growth and N uptake in the WS rice crops were small. However, replacement of DS rice by maize caused a reduction in soil C and N sequestration due to a 33–41% increase in the estimated amount of mineralized C and less N input from biological N fixation during the DS maize crop. As a result, there was 11–12% more C sequestration and 5–12% more N accumulation in soils continuously cropped with rice than in the M-R rotation with the greater amounts sequestered in N-fertilized treatments. These results document the capacity of continuous, irrigated rice systems to sequester C and N during relatively short time periods. This revised version was published online in June 2006 with corrections to the Cover Date.     

EFFECTS OF AGROCHEMICALS ON BROWN PL THOPPER NILAPARVATA LUGENS (STÅL) AND ITS PREDATORY ENEMIES*

Abstract The effects of agrochemicals on brown planthopper (BPH), Nilaparvata lugens, three predators were studied. The results showed that with recommendatory concentrations of 0. 30preti-lachlor EC could cause high mortalities to adults of BPH, Microvelia horvathi and Cyrtorhinus lividipennis; 0. 50 butachlor EC had significant lethal effects on adults of M. horvathi and C. lividipennis, but had negligible effects on BPH and Erogonidium graminicolum; and 40% acetochlor WP had no obvious killing effect to other insects mentioned above, except C. lividipennis. Effects of 0. 50 quincolorac WP, 0. 10 bensulfuron methyl WP, 0. 10 cyclosulfumuron WP and 0. 20 daofuxing WP on these insects were insignificant. As far as fungicides were concerned, 2nd-3rd instar nymphs of BPH and adults of Microvelia horvathi, and Cyrtorhinus lividipennis were obviously sensitive to 0. 40 IBP EC, but 0. 75 chlorothalonil WP 0. 20 tricyclazol WP, 0. 50 carbendazin WP, 0. 25 yekuling WP, 0. 5 jinggangmycin SL and 0. 20 yeqing shuang WP had no evident effects on them. 0. 4635 urea G had also no obvious insecticidal activity on adults of these insects. The results of toxic regression expression and LC₅₀ of IBP, pretilachlor, butachlor and acetochlor to BPH and its predators were determined.