Toxicity of Acorus calamus rhizome powder from Eastern Nepal to Sitophilus granarius (L.) and Sitophilus oryzae (L.) (Coleoptera, Curculionidae)

Powders prepared from sweetflag Acorus calamus rhizomes collected at both high (1700 m) and low (900 m) altitude in Eastern Nepal were admixed with wheat at concentrations in the range 0.05–2% w/w and the wheat infested with Sitophilus oryzae or S. granarius adults. Following a 7 day incubation, the mortality of both species was significantly lower at 20 °C than at 30 °C, and the material collected from high altitude was slightly less toxic than that from low altitude. The moisture content of the wheat (14 or 17%) and the part of the rhizome used to prepare the powder (young or mature growth) had no apparent effect on the toxicity of the preparation. Sitophilus granarius (L.) adults were more tolerant of the material than S. oryzae (L.), while the converse was true for larvae developing in treated grain. An admixture rate of approximately 2% w/w admixed rhizome powder was required to give complete kill of adults of both species following 7 days exposure at 20 °C, while a concentration of 1% w/w either prevented the emergence of adults or killed them rapidly following emergence when wheat containing eggs of either species was incubated for 7–8 weeks at 30 °C.

The β-asarone content of the rhizome powders was determined by GC-MS as 6.4 and 4.7% w/w (mature section of rhizomes collected at high and low altitudes, respectively) and 3.6 and 4.0% w/w (young sections of rhizomes collected at high and low altitudes, respectively). It is anticipated that, under field conditions and in the temperature range 20–30 °C, the initial residue of approximately 1300 mg/kg β-asarone required to disinfest wheat containing these weevil species would decline rapidly due to evaporation.     

Damage Potential,Effect on Germination,and Development of Sitophilus oryzae (Coleoptera: Curculionidae) on Wheat Grains in Northwestern Himalayas

The present investigation was carried out to study the biological parameters and orientation of Sitophilus oryzae (L.) toward wheat cultivar HPW-236 and mixed grains of different cultivars (HPW-155, HPW-236, HPW-249, HPW-349, HPW-360, HS-490, and VL-892). The incubation period, larval period, pupal period, and total life cycle period of S. oryzae was longer when fed on mixed grains as compared to HPW-236. Also, the weevils were more oriented toward HPW-236 and lower germination rates were observed from HPW-236 than mixed cultivars when exposed to S. oryzae. We also evaluated quantitative losses caused by S. oryzae in different cultivars of wheat recommended in the northwestern Himalayas under free-choice conditions. The weevil inflicted greater damage and weight loss in grains of HPW-236 while it was negligible in the case of HPW-360 and HPW-249. HPW-236 which is the most cultivated variety of wheat in northwestern Himalayas proved to be highly susceptible to the weevil and provided a more suitable environment for weevil’s development. Therefore, this particular cultivar can be avoided for prolong storage and the farmers should prefer cultivars such as HPW-360 and HPW-249, which proved to be least affected the weevil.     

玉米花粉生活力研究进展

Grain numbers produced per ear is one of the most important factors affecting grain yield of maize and is determined in a large extent by pollination process.In this paper the research advanced on pollen grain viability and pollination capability of pollen grains,and effects of environmental factors including temperature,humidity,and water content of pollen grain and mineral elements on these characteristics in maize(Zea Mays L.) were reviewed.Measuring of pollen grain viability was also discussed.     

普通玉米3个子粒性状的基因效应分析

为了研究与产量和商品品质有关的子粒性状的遗传机制,利用子粒性状差异明显的6个自交系在加性-显性模型下对子粒长度、子粒容重、HKWI3个子粒性状进行了遗传分析。结果表明,3个子粒性状在多数组合中不符合加性-显性模型,存在上位性效应,其加性效应和显性效应均显著存在,加性效应除子粒长度在多数组合中表现为减效,其余性状为增效;3个子粒性状的显性效应均为增效,且显性效应大于加性效应;上位性效应因材料而异。根据3个子粒性状的遗传特性,通过自交系的选育对其进行选择应该是有效的,一般应在较高世代进行单株选择,同时还应重视亲本间的组配。     

Temperature during grain ripening affects the ratio of type-II/type-I protein body and starch pasting properties of rice (Oryza sativa L.)

The starch and protein properties of rice grain are important factors for sake brewing and these properties are reported to be influenced by temperatures during grain ripening. Amylose content, nitrogen content, protein composition, pasting properties measured by a Rapid Visco Analyser (RVA), and their relationship to temperatures during ripening were investigated in a rice cultivar, Yamadanishiki, which was grown under various conditions in the same experimental field. The average temperature after heading was significantly correlated with amylose content and RVA properties, but not with nitrogen content. Under high temperatures during ripening, a decrease in prolamin, which accumulated in type I protein body (PB-I), and an increase in glutelin, which deposits in type II PB (PB-II), were recognized. The ratio of PB-II/PB-I and RVA pasting temperatures were distinctly increased as the temperature became higher. High temperatures during grain ripening would lead to difficulties in digesting steamed rice grains by Aspergillus oryzae, together with ease in digesting rice protein. The average temperature of 11–20 days after heading showed a higher correlation coefficient than that of 1–10 or 21–30 days, implying that temperatures during the middle stage of grain development would be important in determining the rice component that relates to brewing properties.     

银合欢豆象生物学特性及其防治

银合欢豆象[Acanthoscelides macrophthalmus(Schaeffer,1907)]是银合欢属Leucae植物种子上的重要害虫,除银合欢外,也可蛀食南洋楹(Falcataria moluccana)种子。在75%RH及20~35℃的条件下,卵期为4～12 d。幼虫期为18～37 d,蛹期为5～11 d。成虫寿命17~31 d,雌雄性别比约为1∶1。在75%RH及26℃条件下,银合欢豆象完成1个世代需要44～48 d。在野外,银合欢豆象在幼龄阶段常被一种姬小蜂科(Eulophidae)的柄腹姬小蜂属(Pediobius Walker)寄生。在75%~80%RH及25～30℃条件下,使用56%磷化铝片剂对银合欢豆象进行熏蒸,用药量7~9 g/m3,熏蒸时间48~72 h,成虫、幼虫及蛹死亡率100%。     

下层土壤容重对玉米生育后期叶片衰老的生理效应

采用桶栽法研究了下层土壤容重对玉米生育后期叶片衰老的生理效应。结果表明,随着下层土壤容重的增加,玉米单株叶面积下降;容重越大,叶面积指数下降幅度越大,玉米生育后期叶片衰老速度越快,SOD酶活性降低越多,MDA含量增加越多。     

Influence of treatment of soil with carbofuran on the subsequent performance of insecticides against cabbage root fly (Delia radicum) and carrot fly (Psila rosae)

A sandy loam soil was treated with 2·5 kg carbofuran/ha on each of five occasions between May and October 1984. In 1985, the field performance of benfuracarb, carbofuran, carbosulfan, chlorfenvinphos and furathiocarb against cabbage root fly (Delia radicum) and carrot fly (Psila rosae) was studied in this soil and in identical but previously untreated soil by applying exponentially increasing doses of granular formulations to radish and carrots at drilling. Chlorfenvinphos reduced numbers of larvae of both pests by >90% in both soils but the performance of all the carbamates was significantly worse in the previously treated soil than in the previously untreated soil. Dazomet, a partial soil sterilant, was applied to part of the experimental area in October 1985 and the performance of aldicarb, carbofuran, carbosulfan, chlorfenvinphos and thiofanox against cabbage root fly was assessed in 1986. The efficiency of aldicarb and chlorfenvinphos was not affected by any of the pre-treatments but that of carbofuran and carbosulfan was reduced in all the pre-treated soils, including the soil treated with dazomet. Carbofuran residues in radish were detectable only in plants grown in previously untreated soil. In laboratory incubations, a dustless base formulation of carbofuran was degraded more quickly in pre-treated than in untreated soils but a granular formulation was degraded more slowly and at a similar rate in both soils.     

Field efficacy of wintertime insecticide applications against greenbugs, Schizaphis graminum (Rondani) (Hemiptera: Aphididae) on winter wheat (Triticumaestivum L.)

Winter wheat producers in Oklahoma often combine an insecticide with a top-dress application of nitrogen during late fall and winter to control existing greenbug populations. We evaluated the efficacy of three classes of insecticides applied in cold weather field conditions ranging from −13.3 to 28.9 °C from 2002 to 2004 for greenbug control in winter wheat in replicated small plots. Insecticides provided control ranging from 0% to 98%, but generally responded similarly to temperature. Percent control of greenbugs resulting from applications of dimethoate, chlorpyrifos and λ-cyhalothrin was correlated with maximum, minimum and average daily temperatures that occurred two days post-treatment. While percent control was unique for each insecticide, a combined regression of percent control against average daily temperature predicted that a 95% level of control would be achieved when post-treatment temperatures exceeded 13.6 °C. Rainfall that occurred post-treatment affected the efficacy of dimethoate but did not affect the other insecticides. Insecticide persistence was extended under cooler temperatures, allowing acceptable control 14 days post-treatment if temperatures warmed. The decision to apply insecticides should be made based on existing treatment thresholds for greenbug, but if treatment with an insecticide is warranted, winter wheat producers can expect reasonable control of greenbugs from insecticides applied during the winter, as long as post-treatment temperatures exceed 13 °C within the following 14 days.     

玉米丝黑穗病菌对寄主防御相关酶活性的影响

玉米丝黑穗病是玉米生产上的一种主要病害,对玉米生产造成了严重损失。研究表明:当丝黑穗病菌侵染玉米后,激活寄主体内相关防御酶系,使PAL、SOD、EST和PPO四种酶活性明显提高,抗病品种新铁10的酶活性升高幅度大于感病品种沈单16;而POD和CAT酶活性却下降,抗病品种新铁10的酶活性下降幅度大于感病品种沈单16。不同品种的成株期抗病性与其相关防御酶活性高低明显相关。     

Soak conditions and temperature following sowing influence the response of maize (Zea mays L.) seeds to on-farm priming (pre-sowing seed soak)

On-farm seed priming of maize (i.e. soaking seed in water overnight, 17 h) in the semi-arid tropics has been shown to improve crop establishment and yield but the benefits can be variable. In previous work, this variation was thought to result from the interaction between primed seeds and conditions in the seedbed following sowing. To investigate this interaction, experiments were carried out under controlled temperature conditions that represented those of seedbeds in the semi-arid tropics. The conditions during seed priming and during subsequent germination and emergence were investigated as potential causes of variable seedling emergence relative to that of untreated seeds. Priming advanced emergence from moist sand cores at 30 °C/20 °C (day/night), reduced emergence at 35 °C/28 °C and delayed and reduced emergence at 40 °C/28 °C. In drier cores (drained 8 days) at 35 °C/28 °C, priming advanced germination time and did not decrease final percentage emergence. These results confirmed earlier field observations that the effect of priming in maize can vary and lead to positive, neutral or negative effects. Priming decreased the optimum and ceiling temperatures for germination, and unlike untreated seeds, the relationship between germination rate and sub-optimal temperature was not linear in all cases. Pre-humidifying seeds did not enhance the effect of priming, but aerating the soak water did. These results indicate that variable results from priming recorded in the field were not due to imbibitional damage, but may result from the negative effects of hypoxia during soaking exacerbated by moist conditions and high temperatures at sowing. These effects differed between seedlots of different cultivars, indicating the importance of selecting more tolerant maize hybrids to reduce variation in response to priming following sowing in the field. The implications of these findings for the use of primed seeds in the field are discussed.     

Abundance of Sitona lineatus L. (Col., Curculionidae) in peas (Pisum sativum L.): Effects on yield parameters and nitrogen balance

In a four-year study, we investigated the relationship between the damage to root nodules of organically produced pea (Pisum sativum L.) by the larvae of the pea leaf weevil (Sitona lineatus L.) and the abundance of adult weevils. In addition to studying natural infestations, we established artificial infestations within cages to assess the impact of different weevil densities on yield parameters and determinants of the nitrogen balance. Densities of 0.2 adult S. lineatus per plant (20 individuals per m²) reduced the number of seeds and pods per plant by 18% and 15%, respectively; seeds per pod and thousand-seed weight remained unaffected. A three-fold or five-fold increase in weevil abundance (13–40 or 20 to 100 individuals per m²) did not result in an additional reduction in yield. Moreover, the higher weevil abundance did not adversely affect the N-harvest index or soil nitrogen content. We suspect that the impact of adult S. lineatus on yield and nitrogen parameters is limited by the density-dependent mortality of the larvae. Survival of larvae in turn depends on the nodulation of the plants, which is largely regulated by the supply of water. The assumption that organic cropping systems are at specific risk from the pea leaf weevil was confirmed by increasing population densities during the study period. However, yield losses were independent of adult attack within a wide range of weevil abundance, which indicates the complexity of assessing larval damage based on adult infestation level. An enhanced intraspecific competition among larvae may account for the absence of linear relationships, considering that especially young instars failed to establish in root nodules at higher densities. We found that adult densities of 0.2 individuals per plant and subsequent larval densities of 7 individuals per plant resulted in destruction of 37% of the root nodules on primary roots, which was much below destruction values reported in other studies. In conclusion, we recommend an early monitoring of weevils and early initiation of control strategies because yield losses were caused by even low weevil densities. Finally, the tolerance of P. sativum to S. lineatus was influenced by the yield level, i.e., tolerance to S. lineatus decreased as yield increased.     

Phenolic compounds in raw and cooked rice (Oryza sativa L.) and their inhibitory effect on the activity of angiotensin I-converting enzyme

Whole rice has been widely studied due to the abundance of bioactive compounds in its pericarp. Some of the beneficial effects of these compounds on human health have been attributed to their antioxidant and other biological activities, such as enzyme inhibition. In this work, we evaluated the contents of total, soluble and insoluble phenolic compounds of 6 red and 10 non-pigmented genotypes of whole rice as well as their inhibitory effect on the activity of angiotensin I-converting enzyme (ACE). The effects of cooking on phenolics and their inhibitory activities were also investigated. Red genotypes showed high content of phenolics, mainly soluble compounds, at an average of 409.7 mg ferulic acid eq./100 g, whereas overall lower average levels (99.4 mg ferulic acid eq./100 g) at an approximate soluble/insoluble compound ratio of 1:1 were observed in non-pigmented rice. Pigmented rice displayed a greater inhibitory effect on ACE than non-pigmented rice. In fact, a significant correlation between the content of soluble phenolics and ACE inhibition was observed (r = 0.8985, p < 0.05). In addition to significantly reducing the levels of total phenolics and ACE inhibition, cooking altered the soluble/insoluble compound ratio, especially among red rice genotypes.     

Evaluation of Botanicals for Management of Piercing–Sucking Pests and the Effect on Beneficial Arthropod Populations in Tea Trees Camellia sinensis (L.) O. Kuntze (Theaceae)

The tea green leafhopper Empoasca onukii Matsuda (Hemiptera: Cicadellidae), the orange spiny whitefly, Aleurocanthus spiniferus (Quaintanca) (Hemiptera: Aleyrodidae), and the green plant bugs Apolygus lucorum Meyer-Dür (Hemiptera: Miridae) are the important piercing–sucking herbivores in tea trees Camellia sinensis (L.) O. Kuntze (Theaceae). The goal of this study was to evaluate the laboratory toxicities and field control efficacies of botanical insecticides including matrine, azadirachtin, veratrine, and pyrethrin to three tea pests. Via leaf-dip bioassay, toxicity tests with botanical insecticides indicated that there were significant differences between the LC₅₀ values for botanical insecticides within the same insect species. Matrine had the highest toxicity to E. onukii, A. spiniferus, and A. lucorum with the LC₅₀ values of 2.35, 13.10, and 44.88 mg/liter, respectively. Field tests showed that, among four botanical insecticides, matrine at dose of 9 g a.i. ha⁻¹ can significantly reduce the numbers of E. onukii and A. spiniferus and the infestation of A. lucorum on the tea plants. Furthermore, botanical insecticides matrine and azadirachtin had no obvious influence on the coccinellids, spiders, and parasitoids densities in tea plantations. The results of this study indicated that use of botanical insecticides, such as matrine, has the potential to manipulate the population of E. onukii, A. spiniferus, and A. lucorum and will be an effective and environmentally compatible strategy for the control of tea pests.     

Aerial treatment of the migratory locust, Locusta migratoria (L.) (Orthoptera: Acrididae) with Metarhizium anisopliae (Deuteromycotina: Hyphomycetes) in Australia

Between November 1998 and March 1999, bands of nymphs of Locusta migratoria were aerially treated using a ULV oil formulation of strain FI-985 of Metarhizium anisopliae var. acridum. At a dose of 3–4×10¹² conidia/ha, there was <10% survival of locusts in treated sorghum crops, open grassland or open woodland with grass. Decline was less at lower doses or in dense woodland. During the first week after treatment, bands showed little change in numbers, but then rapidly declined in size and rate of movement. The decline was slower where vegetation was tall or dense, or where bands were large and moved out of the treated area a few days after spraying. In areas where bands were treated with Metarhizium, populations were suppressed in that few adult swarms formed. Adjacent untreated areas had many adult swarms which had to be controlled using chemical insecticides. Preventive locust control, as currently practised in Australia, involves beginning treatment when areas of band and swarm are small and the potential for direct damage limited. The clear demonstration that Metarhizium can suppress small local populations of L. migratoria indicate that it could be a valuable component of preventive control programmes against this species. The delay in mortality when treating with Metarhizium would be no impediment to its use in such programmes.     

Effect of pre-emergence herbicide mixtures on cowpea (Vigna unguiculata (L.) Walp) at Samaru, in northern Nigeria

Field experiments were conducted in the wet seasons of 2005 and 2006 to evaluate the effect of pre-emergence application of herbicides on cowpea. A mixture of metolachlor and prometryn at 1.25+0.08 kg a.i./ha was consistent in better growth and seed yield. However, application of mixtures of metolachlor and terbutryn at 0.99+0.50 kg a.i./ha and ametryn and terbutryn at 1.60+1.00 kg a.i./ha gave lower vigour score of the crop, higher crop injury, smaller canopy spread and lower seed yield. It can be concluded that the metolachlor and prometryn mixture gave good selective weed control and can be used instead of hand weeding in cowpea in northern Nigeria.     

Effect of herbicides and annual weeds on the yield and seed quality of lathyrus (Lathyrus sativus L.)

Field research conducted over six location years has indicated that lathyrus (Lathyrus sativus L.) is a poor competitor with annual weed species. Failure to control annual weeds reduced lathyrus seed yields by 54–95%, depending on the weed species present and their density. Weed competition also reduced thousand-seed weight. Preplant soil-incorporated applications of trifluralin and postemergence applications of sethoxydim controlled wild oat (Avena fatua L.) and green foxtail (Setaria viridis (L.) Beav.). Trifluralin failed to control wild mustard (Sinapis arvensis L.), an important broad-leaved weed in western Canada, but this weed was controlled by both preplant soil-incorporated and postemergence applications of metribuzin. Lathyrus exhibited excellent tolerance to these herbicides, which are currently registered for use on high-acreage crops in Canada.     

光照对小麦的春化效应及其机制初探

为解析光照对春化过程的影响及其机制,以中麦175为材料,比较了光照春化及暗春化28 d时该品种开花时间的差异,并对春化前、春化7 d、14 d、21 d和28 d时,两种春化条件下小麦叶片中春化及光周期相关基因进行了real-time PCR分析。结果表明,与暗春化相比,光照春化使小麦提前开花19.73 d;与春化、光周期相关的基因（TaVRN1、TaVRN2、TaVER2、TaVIL1、TaVIL2、TaVIL3、TaCO1、TaCO2、TaPPD1、TaGI1、 TaLHY和TaTOC1）在光照春化条件下的表达水平较高,这可能是光照春化导致小麦提早开花的主要原因之一,也说明小麦中可能存在未知的TaVRN1调控因子,这些调控因子同时受到光照和低温条件的调控。     

Effect of nitrogen fertilizer on the growth and survival of Rhopalosiphum padi (L.) and Sitobion avenae (F.) (Homoptera: Aphididae) on different wheat cultivars

Increased nitrogen applications to crops influence plant-insect interactions and potentially increase herbivore population growth. The effect of nitrogen applications on the interactions between a wheat host plant, Triticum aestivum, and its herbivores, Sitobion avenae (Fabricius, 1775) and Rhopalosiphum padi (Linnaeus, 1758) was investigated. Adult body weight, fecundity, maturity rate and longevity of the aphids were measured under different nitrogen application on four wheat varieties, Solstice, Einstein, Deben and Alchemy. Adult body weight of R. padi on Alchemy and of S. avenae on Deben was lowest. Fecundity of R. padi was lesser on Deben and Alchemy while fecundity of S. avenae was least on Alchemy. Days to reach maturity were same on all varieties in S. avenae but in R. padi, Deben positively affected the days to reach maturity. Longevity of S. avenae and R. padi was the same on all varieties. N-fertilizer had a positive effect on the adult weight achieved by S. avenae and R. padi. Fecundity and longevity of both species were also positively correlated with N-fertilizer application. In R. padi, N-fertilizer reduced the time to reach maturity but not in S. avenae.     

Yield response of okra, Abelmoschus esculentus (L.) Moench to leaf damage by the flea beetle, Podagrica uniforma Jacoby (Coleoptera: Chrysomelidae)

Yield-related response of okra plants, Abelmoschus esculentus (L.) Moench, to artificial infestation of the flea beetle (Podagrica uniforma Jac.) at different densities (0, 5, 10, 20, 30, and 40 pairs per cage) was studied in screen house and field experiments. In both experiments, increase in beetle density resulted in a significant reduction (P < 0.05) in fruit production, fruit length, fruit width, fresh fruit weight, number of seeds per fruit, 100 seed weight and fresh fruit yield. In addition, higher densities caused more dry matter accumulation in the seeds than in the husk of okra fruits. Compensation was noticed at the 5- and 10-pair levels of infestation in some of the variables measured. Fresh fruit yield reduction was more than 50% when beetle density was increased beyond 20 pairs per cage in both experiments. The lowest density of P. uniforma at which significant reduction (P < 0.05) occurred in fresh fruit yield per cage, when compared with the control, was the 20-pair level, representing the damage threshold of the beetle at which initiation of control measures would be justified. Regression analysis indicated that flea beetle density was linearly associated with fruit damage and fresh fruit yield. Also, chi-square analysis showed that the models derived from the screen house and field experiments were not significantly different (P < 0.05) from each other, and either could be used for prediction purposes.