Nematicidal Potential of the Neem Tree Azadirachta indica (A. Juss)

Plant products are receiving greater attention as prophylactics against several species of plant-parasitic nematodes. Numerous experiments have shown the potential nematicidal value of plant parts and their by-products when incorporated into soil or when the plants themselves are interplanted as seedlings among crop plants. Various products (oils, cakes, extracts, etc.) prepared from the leaves and seeds of the neem plant (Azadirachta indica A. Juss) (Family Meliaceae) have been reported as effective protectants against nematode pests when used as root-dips and seed treatments. Nemato-toxic compounds of the neem plant, especially the azadirachtins, are released through volatilization, exudation, leaching and decomposition. The modes of action of these compounds are complex, and a number of mechanisms in relation to nematode management are yet to be fully explored. This review critically assesses the potential of these products in the management of nematodes in tropical agriculture.     

Effects of clarified neem oil on growth and aflatoxin B1 formation in submerged and plate cultures of aflatoxigenicAspergillus spp.

An increase of 11–31% of dry mycelial mass was observed along with a slight decrease (5–10%) in aflatoxin Bi production in 5-day-old aflatoxigenicAspergillus spp. submerged cultures containing either 0.5 ml or 1.0 ml clarified neem oil (CNO) in 0.1 % Triton solution. Fungal growth and aflatoxin B₁ production were also determined in potato-dextrose-agar petri plate cultures inoculated with aflatoxigenicAspergillus spp. containing an atmosphere of volatiles emitted from 0.25 ml, 0.5 ml, and 1.0 ml CNO added to the plates. After 5 days’ incubation, fungal radial growth was reduced by 7–29% and aflatoxin B₁ production by 0–67%. GC/MS analysis of the head space volatiles of the CNO indicated that the reduction of fungal growth and aflatoxin B₁ was probably due to low molecular weight hydrocarbons, aldehydes, alcohols, and sulfur compounds emitted at 30°C in the dry culture. These results suggest that volatiles emitted from CNO at 30° C in plate cultures were more fungistatic and consequently inhibited aflatoxin production more than neem oil added in liquid cultures.     

Efficacy of new EC formulations of neem oil and pungam oil for the management of sheath rot disease of rice

Neem oil (NO) and pungam oil (PO) based emulsifiable concentrate (EC) formulations,viz., neem oil 60 EC (acetic acid) [NO 60 EC(A)], neem oil 60 EC (citric acid) [NO 60 EC(C] and neem oil + pungam oil 60 EC (citric acid) [NO+PO 60 EC(C)], which had been developed at Tamil Nadu Agricultural University, were evaluated for their efficacy against sheath rot of rice. All three formulations effectively inhibited the mycelial growth of the pathogen,Sarocladium oryzae, underin vitro conditions. There was no significant difference between efficacy of the freshly prepared and stored formulations in arresting the growth ofS. oryzae; efficacy was maintained even after 9 months of storage. These formulations effectively controlled rice sheath rot and led to increased yield in five field trials. Among the various treatments, the formulation NO 60 EC(A) achieved the highest grain yield in four out of five field trials, with a pooled mean grain yield of 4684 kg/havs 3882 kg/ha in the control. NO 60 EC(A) achieved the maximum cost-benefit ratio of 1:4.8, followed by NO+PO 60 EC(C), with 1:3.3.     

Powdered neem seed and cake for management of the banana weevil,cosmopolites sordidus, and parasitic nematodes

Field trials were conducted in Kenya with ‘Nakyetengu’, an East African highland banana cultivar (AAA-EA), highly susceptible to banana pests. Regardless of soil fertility levels, incorporation around the plant base of powdered neem(Azadirachta indica A. Juss.) seed or cake at 60-100 g/mat at 4-month intervals, gave better control of the banana weevil,Cosmopolites sordidus (Germar), and of parasitic nematodes, than that achieved with soil application of Furadan 5G (carbofuran) at 60 g/mat at 6-month intervals. Compared with untreated control, fruit yield in most of the neem treatments was significantly higher, particularly during the second cycle of crop production. Neem application conferred a net economic gain, whereas Furadan application proved uneconomical. Application of powdered neem seed or cake at higher rates (200–400 g/mat) at 6-month intervals caused phytotoxicity, resulting in drying up of banana plants before fruiting, or in ‘chokethroat’,i.e., inflorescence emergence failure.     

The antifeedant effect of neem seed kernel extract and azadirachtin on nymphs ofEyprepocnemis plorans

Acridids belonging to different species and families exhibit large differences in their response to neem components. In this context the antifeedant effect of a methanolic neem seed kernel extract (NSKE) and of azadirachtin (AZA) on fourth-instar nymphs of the acrididEyprepocnemis plorans Charpentier (Saltatoria:Acrididae) was investigated. Nymphs were offered either saccharose-impregnated filter paper disks or leaves of broad beans, treated with neem components. The amount of substrate consumed was determined by weighing the filter paper or by measuring the leaf area. On filter paper both NSKE and AZA were highly active down to the 10⁻⁴% treatment. In the leaf treatment, however, AZA was definitely more active than NSKE, with 100% deterrence at 10⁻⁴% and 10⁻²%, respectively. The methanolic NSKE was somewhat more active than the commercial preparation ‘Neemark’.     

Antifeedant activity of fruit and seed extracts ofMelia azedarach andazadirachta indica on larvae ofSesamia nonagrioides

Methanolic extracts of seeds and fruits of the chinaberry tree,Melia azedarach L. (Meliaceae), showed strong antifeedant activity against 2nd instar larvae ofSesamia nonagrioides Lefèbvre (Lepidoptera: Noctuidae), a very serious pest of maize(Zea mays L.) in Mediterranean countries. Extracts were applied in an artificial diet at concentrations of 1000 and 2000 ppm. The parameters used to evaluate the activity were larval growth rates; quantity of food ingested; phagodepression/phagostimulation index; quantity of frass produced; quantity of material ingested; duration of larval development; and cumulative mortality. Seed extract showed high bioactivity at both doses, while fruit extract proved to be less active, and only at the higher dose used (2000 ppm) did it display a slight antifeedant activity. The activity of theM. azedarach seed extract at the higher dose (2000 ppm) was comparable to that of pure azadirachtin applied at a dose of 1.25 ppm, or to ‘Mubel’, a commercial extract ofAzadirachta indica A. Juss. (Meliaceae), applied at a dose of 75 ppm.     

Biology and integrated pest management for the banana weevil Cosmopolites sordidus (Germar) (Coleoptera: Curculionidae)

The banana weevil Cosmopolites sordidus (Germar) is the most important insect pest of bananas and plantains (Musa spp.). The larvae bore in the corm, reducing nutrient uptake and weakening the stability of the plant. Attack in newly planted banana stands can lead to crop failure. In established fields, weevil damage can result in reduced bunch weights, mat die-out and shortened stand life. Damage and yield losses tend to increase with time. This paper reviews the research on the taxonomy, distribution, biology, pest status, sampling methods, and integrated pest management (IPM) of banana weevil. Salient features of the weevil's biology include nocturnal activity, long life span, limited mobility, low fecundity, and slow population growth. The adults are free living and most often associated with banana mats and cut residues. They are attracted to their hosts by volatiles, especially following damage to the plant corm. Males produce an aggregation pheromone that is attractive to both sexes. Eggs are laid in the corm or lower pseudostem. The immature stages are all passed within the host plant, mostly in the corm. The weevil's biology creates sampling problems and makes its control difficult. Most commonly, weevils are monitored by trapping adults, mark and recapture methods and damage assessment to harvested or dead plants. Weevil pest status and control options reflect the type of banana being grown and the production system. Plantains and highland bananas are more susceptible to the weevil than dessert or brewing bananas. Banana production systems range from kitchen gardens and small, low-input stands to large-scale export plantations. IPM options for banana weevils include habitat management (cultural controls), biological control, host plant resistance, botanicals, and (in some cases) chemical control. Cultural controls have been widely recommended but data demonstrating their efficacy are limited. The most important are clean planting material in new stands, crop sanitation (especially destruction of residues), agronomic methods to improve plant vigour and tolerance to weevil attack and, possibly, trapping. Tissue culture plantlets, where available, assure the farmer with weevil-free material. Suckers may be cleaned by paring, hot water treatment and/or the applications of entomopathogens, neem, or pesticides. None of these methods assure elimination of weevils. Adult weevils may also invade from nearby plantations. As a result, the benefits of clean planting material may be limited to a few crop cycles. Field surveys suggest that reduced weevil populations may be associated with high levels of crop sanitation, yet definitive studies on residue management and weevil pest status are wanting. Trapping of adult weevils with pseudostem or corm traps can reduce weevil populations, but material and labour requirements may be beyond the resources of many farmers. The use of enhanced trapping with pheromones and kairomones is currently under study. A combination of clean planting material, sanitation, and trapping is likely to provide at least partial control of banana weevil.Classical biological control of banana weevil, using natural enemies from Asia, has so far been unsuccessful. Most known arthropod natural enemies are opportunistic, generalist predators with limited efficacy. Myrmicine ants have been reported to help control the weevil in Cuba, but their effects elsewhere are unknown. Microbial control, using entomopathogenic fungi and nematodes tend to be more promising. Effective strains of microbial agents are known but economic mass production and delivery systems need further development.     

Neem seed extract spray applications as low-cost inputs for management of the flower thrips in the cowpea crop

In field trials conducted at the Experiment Station and in a farmer’s field at Mbita near the shores of Lake Victoria, Kenya, applications of 2% or 3% neem seed extract (NSE) @ 200 l/ha with a knapsack sprayer at 38, 47 and 51 days after emergence (DE) of the cowpea crop or 5%, 10% or 20% NSE sprayed @ 10 l/ha with an ultra-low-volume applicator at 31, 39 and 49 DE often significantly reduced the number of larvae of the flower thrips,Megalumthrips sjostedti (Trybom), in cowpea flowers recorded 2 days after each treatment. Also fewer adults occurred in flowers at 51 DE in plots sprayed with 5%, 10% or 20% NSE. Cowpea grain yield was significantly higher in plots sprayed with 20% NSE than in untreated control plots and was comparable to the grain yield obtained in plots sprayed thrice with cypermethrin. Because of the low cost of NSE treatment, the net gain was often more when the crop was sprayed with NSE than with cypermethin. Also, grain quality was superior in neem-treated plots than in untreated or cypermethrin-treated plots.     

香豆素类化合物对朱砂叶螨的触杀活性及定量构效关系研究

采用玻片浸渍法,测定并筛选了25种具有代表性的香豆素类化合物对朱砂叶螨Tetranychus cinnabarinus雌成螨的触杀活性,并构建了一个预测能力较强的定量构效关系(QSAR)模型。结果表明:所有供试化合物对朱砂叶螨均具有触杀活性,且随着处理时间的延长活性升高。处理48 h后,LC50值低于1000 mg/L的化合物有8个,分别是3-(2-苯并咪唑)-7-(二乙氨基)香豆素(1)、3-(2-苯并噻唑)-7-(二乙氨基)香豆素(2)、3-氨基香豆素(3)、3-乙酰基香豆素(4)、4-甲氧基香豆素(5)、6-硝基香豆素(8)、6,7-二甲氧基香豆素(13)和7,8-二羟基香豆素(21),其中化合物1、2、3、5和13的杀螨活性优于药剂对照螺螨酯或与其活性相当;活性最好的化合物为13,处理48 h和72 h后LC50值分别为284.8和122.2 mg/L,其毒力约为螺螨酯的2倍。通过计算得到25种香豆素类化合物的34种物化参数,以此为描述子,经过SPSS相关性剔除、逐步回归分析和校正,得到一个以扭转力、取向力、总能量和分子半径为自变量的QSAR模型,该模型复相关系数R达到0.987,复判定系数R2也达到0.967,通过F检验证明上述模型具有较高的预测能力。     

Effects of margosan-o™, azatin™ and RD9-repelin® on spiders,and on predacious and phytophagous mites

The effects of Margosan-O^TM, Azatin^TM and RD9-Repelin on the phytophagous miteTetranychus cinnabarinus (Boisd.), the predacious miteTyphlodromus athiasae, and the predatory spiderChiracanthium mildei were studied and compared in laboratory experimentsr.-No toxic effect of any of these neem formulations was observed onC. mildei. Margosan-O and Azatin were not toxic to eitherT. cinnabarinus orT. athiasae, but RD9-Repelin was highly toxic to both the phytophagous and the predacious mite.     

The use of host resistance in disease management of rust in common bean

Bean rust, caused by Uramyces appendiculatus, is one of the major diseases in dry and snap bean production world-wide. Numerous advancements in disease management have been made to reduce rust losses. Host resistance is an important component of rust management. However, durability of disease resistance has often been short due to the use of single genes for resistance interacting with extremely high virulence diversity of the bean rust fungus. The challenge to increase durability of resistance has led to strategies such as gene pyramiding of race-specific resistance, selection and use of partial resistance, and investigation and discovery of leaf morphological features that may slow the rust epidemic. Germplasm with multiple sources of rust resistance has been developed in specific bean seed classes and released for public and commercial use in intensive production systems such as those in the United States. However, progress to develop rust resistant germplasm for the subsistence agriculture of Latin America and Africa where intercropping and mixed cultivars dominate the production system has been slow. Incorporation of high yielding, disease-resistant components as partial replacement in farmer's mixtures has the potential to reduce severity in the crop and increase yield in the presence of rust. This strategy would not erode the genetic diversity that is historically known to enhance resistance durability and for many years has given stability in production in the subsistent agriculture systems.     

The use of Solacol® (validamycin) as a growth retardant in the isolation of soil fungi

Solacol^®, a formulation of the antibiotic validamycin, at 0.33% in 2% malt extract agar, reduced the spread of fungi on dilution plates drastically and allowed twice as much incubation time before subculturing; this resulted in an elevated number of species isolated. Using pure cultures of 62 common soil fungi, it was shown that all fast-growing species (exceptPythium ultimum) were efficiently inhibited but not completely suppressed. Inhibition was comparable to that by 0.5% oxgall, though, while this substance completely suppressed several species, Solacol very strongly inhibited onlyGaeumannomyces graminis, Gerlachia nivalis, Harzia acremonioides, Verticillium biguttatum andRhizoctonia solani. In a further experiment each separate constituent of Solacol was tested against 22 fungi at equivalent concentrations. Validamycin strongly inhibitedChaetomium globosum and two Basidiomycetes, though hardly more than the non-ionic detergent which mainly inhibited the other fungi. A few species were, however, more inhibited by Solacol than by the detergent alone. Solacol at 0.33% is a suitable aid in dilution plating of soil fungi, by increasing the number of colonies and species observed.Samenvatting Solacol^®, een formulering van het antibioticum validamycine, remde de groei van schimmels in verdunningsplaten met een concentratie van 0.33% in 2% moutagar en maakte het mogelijk de periode tot afenten met een factor 2 te verlengen; daardoor was het aantal geïsoleerde soorten duidelijk toegenomen. Met reincultures van 62 algemene grondschimmelsoorten werd aangetoond, dat alle snelgroeiende soorten (met uitzondering vanPythium ultimum) voldoende geremd, maar niet volkomen onderdrukt werden. Het remmingspercentage was vergelijkbaar met dat van 0.5% ossegal, hoewel dit laatste sommige soorten volkomen onderdrukte; Solacol remde alleenGaeumannomyces graminis, Gerlachia nivalis, Harzia acremonioides, Verticillium biguttatum enRhizoctonia solani zeer sterk. In een volgend experiment werden de componenten van Solacol t.o.v. 22 fungi apart getoetst in concentraties equivalent aan 0.33% Solacol. Validamycine remde alleenChaetomium globosum en twee basidiomyceten behoorlijk, maar nauwelijks meer dan de niet-ionische uitvloeier, die in hoofdzaak de overige remeffecten veroorzaakte. Enkele soorten werden echter door het complete Solacol veel sterker geremd dan door de uitvloeier alleen. Solacol in een verdunning van 0,33% wordt aanbevolen bij verdunningsplaten voor het isoleren van grondschimmels ten einde het aantal kolonies en soorten te verhogen.     

六种农药对两种果蝇成虫室内毒力和主要解毒酶活性的影响

为明确田间常用农药对伊米果蝇Drosophila immigrans和海德氏果蝇D. hydei的毒力和解毒机制,采用药膜法在室内测定6种田间常用农药原药对2种果蝇实验种群成虫的LC_(10)、LC_(20)和LC_(50),并研究其中3种农药的亚致死剂量(LC_(10)、LC_(20))对果蝇谷胱甘肽S-转移酶(GST)、羧酸酯酶(CarE)、乙酰胆碱酯酶(AchE)3种主要解毒酶活性的影响。结果表明,乙基多杀菌素对伊米果蝇的毒力最大,LC_(10)、LC_(20)和LC_(50)分别为0.29、0.51和1.51 mg/L;甲维盐对海德氏果蝇的毒力最大,LC_(10)、LC_(20)和LC_(50)分别为0.14、0.36和2.09 mg/L;吡虫啉对2种果蝇的毒力均最低。不同亚致死浓度的乙基多杀菌素处理伊米果蝇24 h后,CarE和AchE活性均显著高于对照,而GST活性在低浓度时显著高于对照;高浓度甲维盐仅对海德氏果蝇AchE活性有显著抑制作用;吡虫啉可抑制伊米果蝇AchE和海德氏果蝇CarE活性。表明伊米果蝇和海德氏果蝇可通过改变3种解毒酶的活性来防御杀虫剂对其造成的影响。     

Fire blight of pears in Israel: infection, prevalence, intensity and efficacy of management actions

The pear production area in Israel is 1500 ha, most of which(ca 1200 ha) is located in the northern part of the country. Fire blight (caused by the bacteriumErwinia amylovora (Burrill) Winslowet al.) was first observed in Israel in that region (in 1985) and the disease has prevailed there since then. In a comprehensive survey conducted in Israel in 1996–1999, data were collected and observations were made yearly in one-third to one-half of the pear production area. The aim was to document the prevalence and intensity of fire blight in commercial orchards and to use the data to evaluate the efficacy of management measures employed for its suppression. Regionwise, a severe fire blight epidemic developed in 1996, moderate epidemics developed in 1998 and 1999, and a mild epidemic developed in 1997. The intensity of fire blight in the preceding season in a specific orchard was more influential on current season severity in a season with a mild epidemic than in a season with a moderate epidemic. Analysis of disease onset records and weather data revealed that only a few (1– 3) infection episodes occurred in individual orchards each year. Comparison of fire blight intensity in orchard-plots treated before green tip with copper hydroxide with nontreated plots revealed that the treatment had no effect on disease intensity during bloom. The efficacy of bactericide sprays applied during bloom was not related to the number of sprays applied but to the timing of spraying. Adequate control was achieved in orchard-plots sprayed soon before or after the occurrence of infection episodes. Contribution no. 508/00 from the Inst. of Plant Protection, ARO, Bet Dagan, Israel.     

Phyllonorycter apparella, a new record and a new pest of trembling aspen (Populus tremula) in Turkey

Phyllonorycter apparella (Herrich-Schäffer, 1855) (Lepidoptera: Gracillariidae) is a new record for the Turkish fauna and a new trembling aspen(Populus tremula L.) pest for Turkey. Its biology, damage and infestation ratio were studied in Sankami?. (Kars), Turkey, during 1996 and 1997.P. apparella has one generation a year. The developmental stages of the pest are described briefly. P.apparella hibernates in the adult stage. At the beginning of June, the adults appear. Females deposit their eggs on both leaf surfaces, generally one by one, 7–10 days after emerging. The early instars (sap-feeding larvae) start to mine mostly from the underside of leaves. Each mine has one larva, and each leaf may have up to 26 mines. The last instar (tissue-feeding larva) begins to pupate in the mine after mid August. The adults emerge from mid September to the beginning of October, and move to the trunks of old pine trees, where they hibernate in bark crevices. The infestation level may be as high as 90% of the leaves on some trees.     

Phytotoxicity of solanapyrones A and B produced by the chickpea pathogen Ascochyta rabiei(Pass.) Labr. and the apparent metabolism of solanapyrone A by chickpea tissues

When chickpea shoots were placed in solanapyrone A, the compound could not be recovered from the plant and symptoms developed. These consisted of loss of turgor, shrivelling and breakage of stems and flame-shaped, chlorotic zones in leaflets. In similar experiments with solanapyrone B, only 9.4% (22 μ g) of the compound taken up was recovered and stems remained turgid but their leaflets became twisted and chlorotic and some abscized.Cells isolated from leaflets of 12 chickpea cultivars differed by up to five-fold in their sensitivity to solanapyrone A and this compound was 2.6–12.6 times more toxic than solanapyrone B, depending on cultivar.Glutathione reacted with solanapyrone A in vitro reducing its toxicity in a cell assay and forming a conjugate. Measurement of reduced glutathione concentration and glutathione-S-transferase (GST) activity among cultivars showed that the differences of their means were highly significant and both were negatively and significantly correlated with their sensitivity to solanapyrone A. Treatment of shoots with solanapyrone A enhanced total, reduced and oxidized glutathione content as well as GST activity 1.26-, 1.23-, 1.50- and 1.94-fold, respectively. Similarly, treatment of shoots with the safener, dichlormid, also raised total, oxidized and reduced glutathione levels and GST activity 1.42-, 1.07-, 1.43-, 1.42-fold, respectively. Cells isolated from shoots treated with dichlormid at 150 and 300 μ g per shoot were 2.45 and 2.66 times less sensitive to solanapyrone A, with LD₅₀values of 71.5 and 77.8 μ g ml⁻¹, respectively, as compared to 29.2 μ g ml⁻¹for controls.     

牛筋草内生菌砖红链霉菌CSF09杀虫成分鉴定及活性初步研究

为了从微生物中筛选天然杀虫活性化合物,从牛筋草中分离到1株具有杀虫活性的内生放线菌砖红链霉菌Streptomyces lateritius CSF09。采用大孔吸附树脂提取和硅胶柱层析技术,从CSF09菌株发酵液中分离到1个杀虫活性成分,通过质谱和核磁共振波谱鉴定了其化学结构,并初步测定了该化合物对3龄粘虫幼虫和家蝇成虫的杀虫活性。结果表明:该菌株发酵液中的杀虫活性成分为4-甲氧基水杨醛,发酵单位约为13 mg/L;4-甲氧基水杨醛对家蝇和粘虫均表现出一定的触杀活性,其中对家蝇的LD50值为1.51 μg/头,对粘虫毒力较弱,以10 μg/头剂量处理时校正死亡率仅为36.6%;4-甲氧基水杨醛杀虫活性的突出特性是作用迅速,其击倒中时（KT50）大多在5 min以内。研究表明,4-甲氧基水杨醛具有一定的卫生杀虫剂开发应用潜力。     

不同覆膜方式对山旱地菜豆土壤水分及利用效率的影响

以秋季和春季半膜平覆、全膜平覆、全膜双垄沟6种覆膜方式为处理,研究了不同覆膜方式对山旱地菜豆土壤水分及其利用率等的影响.结果表明,秋季全膜双垄沟和秋季全膜平覆较春季全膜双垄沟、秋季半膜平覆、春季全膜平覆和对照春季半膜平覆在播种时0～ 100 cm土层中土壤贮水量分别提高7.62％～14.20％、7.44％～14.02％...     

Accumulation of phytoalexins in leaves of plane tree (Platanus spp.) expressing susceptibility or resistance toCeratocystis fimbriata f. sp.platani

Inoculation of leaves of resistantPlatanus occidentalis and susceptiblePlatanus acerifolia leaves withCeratocystis fimbriata f. sp.platani, the canker stain disease agent, induced foliar necrosis and biosynthesis of two phytoalexins, scopoletin and umbelliferone. Foliar symptoms keep localized and accumulation of coumarin phytoalexins was rapid for incompatible interactions. Necrosis spread widely and accumulation of these phenolic compounds was much later and lower for compatible interactions. The differential response could be used in a genetic improvement program for resistance against canker stain.