Effect of Intercropping Pattern on Stem Borer Infestation in Pearl Millet (<em>Pennisetum glaucum</em>L.) Grown in the Nigerian Sudan Savannah

Fields experiments were conducted at the Department of Crop Protection, Faculty of Agriculture, University of Maiduguri Teaching and Research Farm, Maiduguri during 2010 and 2011 cropping seasons to investigate the effects of intercropping pattern on stem borer pest infestation in pearl millet (Pennisetum glaucum L.) intercropped with ground nut (Arachis hypogea L.). A split-plot design was used to test the intercrop pattern of 1:0 ratio (sole millet), 1:1 ratio (1 millet row to 1 ground nut row), 2:1 ratio (2 millet rows to 1 ground nut row) and 1:2 ratio (1 millet row to 2 ground nut rows). The results obtained showed that the intercrop pattern of 1:2 ratio and 1:1 ratio yielded less stem borer infestation and abundance in pearl millet, and as well supported high panicle weight and grain yield. In addition to recommending either of these two intercropping patterns to pearl millet farmers for more effective stem borer pest management, results further show the need for identification of effective intercropping patterns in other cropping systems.

Molecular diagnosis and direct quantification of cereal cyst nematode(Heterodera filipjevi) from field soil using TaqMan real-time PCR

Heterodera filipjevi continues to be a major threat to wheat production worldwide.Rapid detection and quantification of cyst nematodes are essential for more effective control against this nematode disease.In the present study,a TaqManminor groove binder(TaqMan-MGB)probe-based fluorescence quantitative real-time PCR(qPCR)was successfully developed and used for quantifying H.filipjevi from DNA extracts of soil.The primers and probe designed from the obtained RAPD-SCAR marker fragments of H.filipjevi showed high specificity to H.filipjevi using DNA from isolatesconfirmed species of 23 Heterodera spp.,1 Globodera spp.and 3 Pratylenchus spp.The qPCR assay is highly sensitive and provides improved H.filipjevi detection sensitivity of as low as 4^(-3) single second-stage juvenile(J2)DNAs,10^(-3) female DNAs,and 0.01μgμL^(-1) genomic DNAs.A standard curve relating to the threshold cycle and log values of nematode numbers was generated and validated from artificially infested soils and was used to quantify H.filipjevi in naturally infested field soils.There was a high correlation between the H.filipjevi numbers estimated from 32 naturally infested field soils by both conventional methods and the numbers quantified using the qPCR assay.qPCR potentially provides a useful platform for the efficient detection and quantification of H.filipjevi directly from field soils and to quantify this species directly from DNA extracts of field soils.

杂草种类、叶龄及药后降水时间对烟嘧磺隆药效的影响

温室盆栽条件下研究了反枝苋 Amaranthus retroflexus、马唐 Digitaria sanguinalis、稗草Echinochloa crus- galli、牛筋草 Eleusine indica和苘麻 Abutilon theophrasti5种杂草对烟嘧磺隆的敏感性。结果表明 :反枝苋和稗草对该药剂最敏感 ,而苘麻对烟嘧磺隆的耐药性最高。药液中添加2 .5 m L/ L的有机硅助剂 Silwet L- 77提高了对除马唐以外的所有草种的防除效果 ,表明在作用于马唐时 Silwet L- 77与烟嘧磺隆之间存在拮抗作用。杂草叶龄对烟嘧磺隆的药效有明显的影响 ,3～5叶期施药 ,防效高达 89.9%以上 ,而 7叶期的防效只有 75 %。药后 1.5 h和 3.0 h降水 3mm降低了烟嘧磺隆的防效 ,但药后 6 .0 h降雨对药效无显著影响。烟嘧磺隆与 Silwet L- 77混用 ,可提高药剂对反枝苋的抗雨水冲刷能力 ,但对马唐的效果没有提高。

杂草种子空间扩散模型的建立

为通过模型分析和模拟来制定控制杂草的优化策略,我们设计并完成了一个杂草种子风扩散的室内实验。本文根据实验获得的数据建立了杂草种子扩散的空间模型。结果表明:杂草种子在任意方向上的扩散服从近似的高斯分布;在实验条件下,杂草种子扩散的空间分布型随风速的变化而变化。著名的Howard等〔5〕的杂草扩散模型是本文所建模型的特例。据此,我们推断Howard等〔5〕的模型所表示的分布型与一定高度的杂草种子在中等风速条件下扩散的分布型相似。

探讨使用野外随机取样推断随机变量概率分布的数学方法——杂草研究作为一个例子1

我们在生态学研究中涉及到的大多数变量呈现出随机性,因而可以认为它们就是随机变量。概率分布是研究随机变量变化规律的基础,如何利用野外取样来推断检验随机变量的分布是本文要解决的主要问题。本文扩展了回归方法的应用,使其能用来推断一个随机变量的分布函数,并且该推断还能被统计检验。作为一个应用实例,该方法被用于确定杂草种子在特定条件下扩散的分布函数。在此条件下,该杂草种子扩散为近似的高斯(正态)分布。

Efficacy of aqueous leaf extracts and synthetic insecticide on pod-sucking bugs infestation of cowpea (Vigna unguiculata (L.) Walp) in the Guinea Sa-vanna Region of Nigeria

Pod-sucking bugs (PSBs) infestation by Ano-plocnemissp./ Riptortussp./Clavigrallasp./Nezaraviridula( Linnaeus) greatly limits cowpea (Vignaunguiculata (L.) Walp) production throughout sub-Saharan Africa. The efficacy of aqueous leaf extracts (ALEs) (5 percent weight/volume concentration) of three botanicals and one synthetic insecticide against PSBs infestation was thus evaluated. The botanicals tested include Aza- dirachtaindicaA. Juss, Chromolaenaodorata (L.) and Ricinuscommunis (L.), whilst the synthetic insecticide was Uppercot 500 EC ( Lambda cyhalothrin 30 g + Dimethoate 250 g ). The effects of these treatments on the number of PSBs/ pods/seeds, pod/seed weight and grain yield were assessed during 2008 and 2009 rainy seasons in Bayo, Borno State, Guinea Savanna region, Nigeria. The number of PSBs was lower on crops treated with Uppercot 500 EC (0.00 - 0.31). This was followed by crops treated with the ALEs ofA.indica/C.odorata (0.31 - 1.33) and R.communis (0.72 - 3.72) than the untreated (3.06 - 5.64) ones.The number of pods/pod weight per plant, seeds/seed weight per pod and total grain yield were generally higher on cowpea crops treated with Uppercot 500 EC (26/17 g, 14/19 g and 1618 kg). This was followed bycrops treated with the ALEs of A.indica/C.odorata (23 - 25/14 - 15 g, 12 - 13/15 g and 1268 - 1310 kg) and R.communis( 21/13 g, 11/14 g and 972 kg) than the untreated (16/9 g, 7/10 g and 312 kg) ones. Although Uppercot 500 EC was most effective inprotecting cowpea against PSBs attack, theALEs of A.indica and C.odorata appreciably protected treated crops against infestation, giving relatively high total grain yield. Both botanical scan thus serve as alternatives to synthetic insecticides for managing PSBs attack on cowpea.

Stabilisation of Pb in Pb Smelting Slag-Contaminated Soil by Compost-Modified Biochars and Their Effects on Maize Plant Growth

Compost has been used to stabilise lead (Pb) in soil. However, compost contains a high level of dissolved organic matter (DOM) which may make Pb bioavailable in plant and thereby limiting its effectiveness and application. Addition of biochar to compost can reduce this effect. Rice husk (RH) and Cashew nut shell (CNS) biochars and compost-modified biochars were used in comparison to compost for stabilizing Pb in lead smelting slag (LSS)-contaminated soil (Pb = 18,300 mg/kg) in Nigeria. Efficiency of Pb stabilisation in control and amended soils was assessed using CaCl2 batch leaching experiment and plant performance. In pot experiments, maize plant was grown on the contaminated soil and on soil treated with minimum and optimum doses of the amendments singly and in combination for 6 weeks. Agronomical and chemical parameters of the plants were measured. CaCl2-extractable Pb in the untreated soil was reduced from 60 mg/kg to 0.55 mg/kg in RHB amended soils and non-detectable in other amended soils. RH-biochar/compost increased plant height, number of leaf and leaf area more than the others. Similarly, at minimum rate, it reduced root and shoot Pb by 91% and 86.0% respectively. Compost-modified rice husk biocharstabilised Pb in lead smelting slag contaminated soil reduced Pb plant uptake and improved plant growth. Lead stabilisation through the use of rice husk biochar with compost may be a green method for remediation of lead smelting slag-contaminated soil.

Mutagenic Effects of Gamma Radiation on Eight Accessions of Cowpea (Vigna unguiculata [L.] Walp.)

Mutagenesis is used for creating new genetic variability in cultivar improvement. Optimal mutagenic treatment is required for effective mutation induction in crop species. Therefore, radio-sensitivity of cowpea accessions to gamma irradiation was investigated. Seeds of eight cowpea accessions were irradiated with 60Co gamma radiation doses of 100, 200, 300, 400 and 500 Gy. The seeds were sown in pots to evaluate the treatment effects on seed germination (SG), seedling survival (SS) and growth habits of M1 generation. Data were analyzed using descriptive statistics. Low rates of SG (10% - 45%) were recorded at higher doses (500 - 400 Gy) in Ife Brown (IB) and its derivatives, whereas high SG rates (74% - 94%) were observed in IT90K-284-2 across all treatments. Percentage SS was inversely related to gamma dosage. A wide range of LD50 for SG (329 - 1054 Gy) and SS (149 - 620 Gy) were observed across the cowpea accessions. Low LD50 scores for SG (329 - 516 Gy) and SS (149 - 357 Gy) were observed among cowpea with rough seed coat, whereas cowpea with smooth seed coat recorded higher LD50 for SG (521 and 1054 Gy) and SS (449 and 620 Gy). Seed germination LD50 and SS LD50 were highly correlated with mean coat thickness (0.899 and 0.937) than mean seed weight (0.621 and 0.678). Gamma irradiation of cowpea seed at low dosage (100 Gy) increased the vigor of M1 seedlings with respect to primary leaf area, terminal leaflet area, seedling height and plant height at six weeks. Doses of 200 Gy and above resulted in a progressive reduction in vigor of plant and seed setting of cowpea. Radio-sensitivity varied with cowpea genotype and was associated with seed testa texture, thickness and seed weight. Low gamma irradiation treatment (100 Gy) may be used to enhance seedling vigor, vegetative growth and yield of cowpea at M1 generation.

Effects of Initial Infestation Levels of Callosobruchus maculatus (F.)(Coleoptera: Chrysomelidae) on Cowpea and Use of Nicotiana tabacum L.Aqueous Extract as Grain Protectant

This study determined the effects of initial infestation of cowpea seeds （Ife brown variety） with different insect densities （0, 2, 4 and 6 pairs per 50 g seeds） of Callosobruchus maculatus （F.） and evaluated the effects of aqueous leaf extract of Nicotiana tabacum L. on C. maculatus in the laboratory. It was observed that adult beetle population increased significantly （p〈0.05） with increase in insect density. The increase in population of beetles and corresponding weight loss of the seeds in different levels of infestation showed that the cowpea variety was susceptible to beetle infestation, emergence and survival of progeny. Significantly more adults emerged on higher infestation compared to lower and no infestation. In Nigeria, Nicotiana tabacum L. is a locally available plant, with known insecticidal properties. The plant leaf extract was easily extracted with water and confirmed its effectiveness as a protective agent for stored cowpea seeds. Experiment was conducted to assess the effects of aqueous extracts ofN. tabacum at 0, 0.1, 0.2 and 0.3 mL＂ 50 g-1 cowpea seeds on C. maculatus. Data was recorded and showed varying levels of effectiveness against C. maculatus. Result showed that seed appearance was dependent on levels of insect population, while N. tabacum aqueous extract exerted effects on survival of C. maculatus. Aqueous leaf extract of N. tabacum probably contained some insecticidal properties which might have significantly conferred beetle mortality and reduced beetle emergence leading to a decrease in seed weight loss.

Evaluation of Insecticidal Potential of Capsicum chinense Jacq. and Aframomum melegueta K. Schum. Against Trogoderma granarium Everts(Coleoptera: Dermestidae) in Groundnut

The insecticidal potential of seed powders of Capsicum chinense Jacq. （Solanaceae） and Aframomum melegueta K. Schum. （Zingiberaceae） was tested against Trogoderma granarium （Coleoptera： Dermestidae） in the laboratory at （28±2）℃ and 70%± 5% relative humidity. The seed powders were tested at the rates of 0.0%, 0.5%, 1.0% and 1.5% （w/w） of groundnut seeds replicated three times. At the highest rate of treatment, C. chinense caused 56.7% and 76.8% larval mortality at 3 and 7 days post treatment （DPT） respectively while A. melegueta exerted 53.4% and 73.8% larval mortality at 3 and 7 DPT, respectively. Results showed that insecticidal potential of the seed powders against adult mortality of T. granarium and seed damage followed similar trend. The various rates of C. chinense seed powder performed better than .4. melegueta seed powder in causing larval and adult mortality and in reducing seed damage. The activity of the seed powders on mortality of the insect, seed weight loss and seed damage were exposure time and rate dependent. A significant reduction （p〈0.05） in seed weight loss and seed damage was recorded among the treatments and maximum reduction was observed in the seeds treated with the highest rate of C. chinense seed powder. Percentage seed damage significantly （p〈0.05） decreased with increase in the rate of treatment while the highest seed weight loss and seed damage were obtained in the control. The study showed that C. chinense seed powder had higher activity against the test insect pest than .4. melegueta seed powder. The two seed powders had high bio-activity against the insect and therefore could be used in formulating environment friendly plant-derived insecticide.

Laboratory Assessment of Susceptibility of Maize Varieties to Post-harvest Infestation By Sitophilus zeamais(Mostchulsky)(Coleoptera: Curculionidae)

A study was carried out to determine the relative susceptibility of six maize(Zea mays L.) varieties to maize weevil,Sitophilus zeamais Motschulsky(Coleoptera: Curculionidae). It was conducted at Department of Crop Protection Laboratory,University of Ilorin, Nigeria at ambient temperature of 28±2℃ and 68%±3% relative humidity. Samples of the varieties were infestedwith five pairs of S. zeamais adults in their respective containers arranged in completely randomized design with three replications.Data were collected on moisture content, adult mortality, adult emergence, grain loss and grain damage. The index of susceptibilityand means of damage parameters were used to determine susceptibility of the maize varieties. The results showed that 2008 SYNEE W DT STR was highly resistant and 2004 TZE-W POP STR C4 was moderately resistant, while 2004 TZE-Y-POP STR C4,99 TZEE-Y-STR, EV99 QPM and TZE-Y-POP DT STR QPM C_0S1 were susceptible. Under artificial infestation, the weevils hadsignificantly longer survival period in the susceptible varieties than those in the resistant genotype. It could be concluded that thesusceptible varieties already released to farmers should be protected from maize weevil damage.

Efficacy of Botanical Insecticides in Control of Flea Beetle (Phyllotreta cruciferae) on Cabbage (Brassica oleracea Linn) on Field

An investigation of effect of Latana camara, Tephrosia vogelii and Zingiber officinale applied at 5%, 10% and 25% concentrations on flea beetle of cabbage was conducted on the Teaching and Research Farm of the Ladoke Akintola University of Technology Ogbomoso in the early seasons of 2011 and 2012. The experiment consisted of 11 treatments laid in a Randomized Complete Block Design （RCBD） with three replications. Data were subjected to analysis of variance and significant means were compared using the Least Significant Difference （LSD） at p〈0.05. All the tested plant extracts exhibited moderate efficacy in the control of flea beetle. The treatment plant extracts performed as well as synthetic insecticides （0.76±0.05 and 0.76±0.05, respectively）. It was discovered that 25% w/v of Z. officinale gave the best yield of 0.50 kg · hm-2. The result showed that extract of T. vogelii （0.71±0.00） and L. camara （0.96±0.23） could suppress flea beetle population at different hours of spraying, while Z. officinale showed an effect at 48 HAS （0.71±0.00） and 72 HAS （0.76±0.05） alter spraying.

Molecular and morphological characterization of stunt nematodes of wheat, maize, and rice in the savannahs of northern Nigeria

Stunt nematodes(Tylenchorhynchus spp.)are obligate migratory root ecto-parasitic nematodes found in the fields of many cultivated crops.These nematodes,with phyto-sanitary potential,are frequently ignored or misdiagnosed as pests,and this may pose a threat to food security.The accuracy of its identification based on a morphological approach has been challenged recently,due to the overlapping of the morphological and morphometric characters of the species.Consequently,the objective of this study is to identify and characterize stunt nematodes present in 54 fields cultivated with cereal crops(wheat,maize and rice)in the savannahs of northern Nigeria,using integrative taxonomy and molecular approaches.The molecular and morphological studies identified and confirmed the presence of T.annulatus as the occurring specie in the savannahs of northern Nigeria.The phylogenetic analysis was carried out using the internal transcribed spacer(ITS)and 28S genes of ribosomal DNA further confirmed the presence of T.annulatus.The first molecular characterization and sequences of the ITS and 28S rDNA gene for T.annulatus from Nigeria were provided by this research.Also,according to our literature search,this is the first report on T.annulatus in wheat,maize and rice in the savannahs of northern Nigeria.Further study to test the pathogenicity of the parasitic nematode species found in this survey is recommended for the prioritization and development of efficient management strategies.

Nutritional Components of Groundnut Seed Varieties and Their Damage by Khapra Beetle,Trogoderma granarium Everts

A laboratory experiment was carried out to determine the response of six groundnut varieties to infestation by larvae of Trogoderma granarium Everts （Coleoptera： Dermestidae） and their nutritional constituents. The improved groundnut varieties used included SAMNUT 10, RMP-91, SAMNUT 19, SAMNUT 23, EX-DAKAR and RRB. The crude fat content varied significantly among the varieties from 32.7% to 53.1% in EX-DAKAR and RRB, respectively. The seed varieties were not significantly different in crude protein, ash and moisture content. The moisture content ranged between 6.6% and 8.9% in EX-DAKAR and SAMNUT 19 varieties, respectively. The crude protein content ranged between 19.7% and 31.3% in SAMNUT 19 and EX-DAKAR, respectively. The ash content varied between 3.0% and 7.4% in RRB and RMP-91 varieties, respectively. The results showed that the seeds were attacked by the 4th instar larvae of T. granarium as indicated by percentage seed weight damage, seed weight loss and dust production. SAMNUT 10 variety had the least seed damage of 33.1%, 41.4% and 43.7% in 1 month, 2 and 3 months post-infestation. In view of the damage, it was evident that SAMNUT 10 variety had the least percent seed damage and loss suggesting the possible inclusion of the variety in breeding programme against the insect pest.

Effect of Infestation of <i>Alabama argillacea</i>(Lepidoptera: Noctuidae) at Different Ages of Cotton Plants in Yield

The cotton leafworm is an important defoliating pest of cotton in Brazil, and occurs in all regions where the crop is cultivated. The purpose of this study was to evaluate the effect of larval densities of A. argillacea after different infestation periods on the yield components of four cotton cultivars. The experiment was carried out in Pindorama, SP, Brazil, in the 2008/2009 growing season. The cultivars IAC-25, DeltaOPAL, Fibermax 966 and Fibermax 993 were artificially infested with A. argillacea larvae at three times (30, 60 and 90 DAE) and four densities (0, 2, 4, and 6 larvae per plant). The average boll weight (g), fiber percentage (%), 100-seed weight (g) and yield (kg·ha-1) were evaluated. With increasing infestation density of A. argillacea, the cotton yield of the cultivars decreased. The presence of larvae significantly reduced the weight of 100 seeds of cultivar Fibermax 966. Initial infestations reduced the boll weight of IAC-25 and DeltaOPAL, while cultivars Fibermax 966 and Fibermax 993 were most affected by late infestations. Early infestation compromised fiber percentage of cultivar DeltaOPAL and late infestations were most harmful to cultivar Fibermax 966. Early A. argillacea infestation reduced the yield of DeltaOPAL, while infestations 60 DAE caused the most damage to IAC-25, and the other cultivars were not affected by the moment of infestation.