Farmers' knowledge and perception of grain legume pests and their management in the Eastern province of Kenya

Grain legumes play an important role in community livelihood and in the national economy in Kenya. Unfortunately, in many African countries, production doesn't satisfy the demand in grains due to various constrains. Understanding farmers practices and behavior in the management of grain legume pests is a crucial step in the development of sustainable management strategies. A total of 216 farmers were surveyed in eight districts of eastern Kenya to evaluate farmers' knowledge and perceptions of grain legume pests; to examine current pest management practices, and to identify other production constraints. Grain legumes are grown by a wide age-group of farmers, with both genders equally represented. Chemical control remains the main pest management strategy, and, to ensure pesticide effectiveness, farmers also use increased application rates, chemical alternation, frequent application and mixtures of chemicals. While farmers used other control measures, they showed only limited interest in biological control. The majority of the farmers had experience in grain legume farming and were able to identify the major pests, which were the legume flower thrips Megalurothrips sjostedti Trybom, the cowpea aphid Aphis craccivora Koch and the legume pod borer Maruca vitrata Fabricius. Our survey revealed that education and proximity to extension services contributed significantly to farmers' knowledge of grain legume pests, suggesting the need to provide continuous training and capacity building on integrated pest management in grain legume farming. The study also suggests integration of other pest management strategies such as the use of early maturing varieties, biopesticides and biofertilizer to reduce the use of chemical for sustainable pest management.     

Phenolic content,anthocyanins and antiradical capacity of diverse purple bran rice genotypes as compared to other bran colors

Anthocyanins are flavonoids, a subgroup of phenolic compounds in bran of purple rice that have shown health benefits in animal studies and human clinical trials. We studied the genetic diversity of the concentrations of total phenolics, flavonoids and anthocyanins, and, antiradical capacity in diverse purple rice brans. More than 13-, 12-, 25- and 8-fold variations were found for these respective traits. Cyanidin-3-glucoside and peonidin-3-glucoside were the major anthocyanins identified. The color parameter b* of whole grain rice was correlated with anthocyanins and can be used as a non-destructive quick screening tool. Purple brans that accumulated both anthocyanins and proanthocyanidins had the highest total phenolics, total flavonoids, and oxygen radical absorbance capacity among all color brans. Purple brans had the widest genotypic diversity of these chemical traits, followed by red, brown, light brown, and white. In terms of antioxidant properties of total flavonoid compounds in the sample extracts, purple and red brans had similar reducing capacity per unit of total flavonoids; while purple bran had higher oxygen radical absorbance capacity per unit of total flavonoids. In conclusion, new rice cultivars with colored bran having specific amounts and types of phenolic compounds can be developed using traditional breeding.     

Effect of green-belly stink bug,Dichelops furcatus (F.) on wheat yield and development

The green belly stink bug, Dichelops furcatus (F.) (Hemiptera: Heteroptera: Pentatomidae) is a pest of corn and soybean in southern Brazil. It also occurs on wheat, but information on its damage to this crop is limited. To determine the need for sustainable IPM programs, the impact of this bug on wheat production should be determined. Studies were conducted in the screenhouse with 1, 2 and 4 bugs caged for 16 days on single plants, cv. ‘BRS Parrudo’. During the vegetative period (plants ca. 25 cm tall), all infestation levels significantly reduced plant height and ear head length, but did not reduce grain yield. Feeding damage caused tissue necrosis on leaves. During the booting stage, grain yield was significantly reduced with 2 and 4 bugs per plant; ear heads were small, discolored and abnormally developed. In 2013 and 2014 field trials, plants were infested for 18 days with 2, 4 and 8 bugs per m² at vegetative, booting, and milky grain stage. At these infestation levels, there was no significant reduction in grain yield. There was a significant decrease in the number of normal seedlings resulting from seeds exposed to 8 bugs per m² at the milky grain stage. Results suggest that, in general, there is no need to control D. furcatus on wheat, unless numbers are ≥8 bugs per m² during reproductive period.     

Use of the response of two growth stages of cowpea to different population densities of the coreid bug, Clavigralla tomentosicollis (Stål.) to determine action threshold levels

The effects of increasing the population density of the cowpea coreid, Clavigralla tomentosicollis Stål., up to a maximum of 32 pairs of insects per cage, infested on cowpea at either early flowering or mid pod-fill, were studied in potted plants and field cages. Overall, the results show that increasing insect density resulted in a corresponding increase in damage to the crop (measured as abscission of fruiting bodies and as damage to pods and seeds). Yield reduction was approximately proportional to the bug population when low, with highly significant correlation coefficients. Damage to the crop and yield reduction were more drastic when infestation was made during flowering as opposed to infestation at podding; although there was some compensation of damage to fruiting bodies during the former growth phase, this was not sustained with increasing pest density. Suggested pest densities at which control measures should be initiated are two insects (fourth instar and over) per 10 plants at flowering and four insects at podding. Further studies on damage thresholds in multiple pest scenarios are suggested.     

Cowpea seed treatment with carbosulfan: potential for control of seedling pests

Results from three field trials and a screenhouse study conducted in 1985 and 1986 using carbosulfan (Marshal 25 ST) insecticide dust formulation at 0, 10, 20, 30 and 40 g/kg cowpea seed indicated that infestation and/or damage by aphids, foliage beetles and leafhoppers was satisfactorily reduced with treatment levels above 20 g carbosulfan/kg seed. The period of activity of the different treatments ranged from 15 to 23 days for various pests in the screenhouse, and slightly longer in field trials. Post-flowering pests were, however, not controlled at any of the rates tested. The ease of application and high dermal LD₅₀ (> 2000 mg/kg rabbit) make Marshal 25 ST a very attractive option for use by small-scale farmers as a component of an integrated pest management strategy in locations where these pests are important and adequate levels of genetic resistance are not available.     

Evaluation of Bt (Bacillus thuringiensis) rice varieties against stem borer (Chilo suppressalis)

Three transgenic rice varieties namely Khazar, Neda and Nemat, all containing a cry1Ab gene, were evaluated through PCR analysis and field examinations for their resistance at natural infestation of insect pests during 2007. The results showed that all transgenic varieties produced 1.2 kb PCR product derived from application of cry1Ab gene. In field conditions, transgenic varieties exhibited high levels of resistance against natural infestation of stem borer and the damaged plants based on dead heart or white heat for them were less than 1%. Moreover, in stem-cut bioassay 100% of released larvae died within four days after infestation. These results demonstrate that expression of cry1Ab gene in the genome of transgenic varieties provided season-long protection from the natural infestation of lepidopteran insects.     

Phase II-Inducing,Polyphenols Content and Antioxidant Capacity of Corn (<Emphasis Type="Italic">Zea mays</Emphasis> L.) from Phenotypes of White,Blue, Red and Purple Colors Processed into Masa and Tortillas

White, blue, red and purple corns (Zea mays L.) were lime-cooked to obtain masa for tortillas. The total phenolics and anthocyanins content, antioxidant activity expressed as total reducing power (TRP), peroxyl radical bleaching (PRAC), total antioxidant activity (TAA) and quinone reductase (QR) induction in the murine hepatoma (Hepa 1 c1c7 cell line) as a biological marker for phase II detoxification enzymes were investigated. Among the extracts prepared from raw corn varieties the highest concentration of total phenolics, anthocyanins, antioxidant index and induction of QR-inducing activity were found in the Veracruz 42 (Ver 42) genotype. The nixtamalization process (masa) reduced total phenolics, anthocyanins and antioxidant activities and the ability for QR induction when was compared to raw grain. Processing masa into tortillas also negatively affected total phenolics, anthocyanin concentration, antioxidant activities, and QR induction in the colored corn varieties. The blue variety and its corresponding masa and tortillas did not induce QR. Ver 42 genotype and their products (masa and tortilla) showed the greatest antioxidant activity and capacity to induce QR     

Farmers’ perceptions and management practices of insect pests on stored sorghum in southwestern Ethiopia

Surveys were undertaken in six districts of southwestern Ethiopia from July to October 2003 to investigate farmers’ perceptions and management practices of insect pests on traditionally stored sorghum. The survey involved 138 randomly selected farmers who were interviewed using a semi-structured questionnaire. Storage insect pests were perceived as the major insect pests of sorghum. The majority of the farmers estimated sorghum yield losses of up to 50% due to insect damage during storage. High temperature and lack of storage hygiene were cited as the major factors resulting in insect infestation of stored sorghum. Infestations of stored sorghum insect pests were common on different forms of sorghum, which stored in various types of farm storage. Farmers classified sorghum varieties according to the level of resistance to stored sorghum insect pests. Only about 32% of the farmers had access to chemical insecticides for the control of stored sorghum insect pests, while the majority of them used cultural practices and locally available plant materials as storage protectants.     

Seasonal abundance of the mirids, Lygus lucorum and Adelphocoris spp. (Hemiptera: Miridae) on Bt cotton in northern China

Lygus lucorum Meyer-Dür, Adelphocoris fasciaticollis Reuter and Adelphocoris lineolatus (Goeze) (Hemiptera: Miridae) are important secondary insect pests in cotton fields in northern China. The seasonal dynamics of their mixed populations on a transgenic variety expressing the insecticidal Bt protein Cry1A, and a cotton line expressing proteins of Cry1A and CpTI (cowpea trypsin inhibitor gene) were compared to seasonal dynamics on similar but non-transgenic varieties from 1998 to 2001. No significant differences were detected between population densities of these bugs on unsprayed normal cotton and unsprayed transgenic cotton. However, mirid damage on unsprayed transgenic cotton was significantly higher due to a reduced number of insecticide sprays against Helicoverpa armigera compared with the number of sprays in the normal cotton. This suggests that the mirids have become key insect pests in transgenic cotton fields, and that their damage to cotton could increase further with the expansion of the area planted to transgenic cotton if no additional control measures are adopted.     

Effects of infestation on the nutrient content and physiocochemical properties of two cowpea ( Vigna unguiculata) varieties

Two cowpea varieties (Ife-brown and Kano-white varieties) were used for the study. The effects of insect infestation on the chemical composition and physicochemical properties of these cowpea seeds were studied. The proximate composition, mineral content, total starch, total soluble sugars, bulk density, fat and water absorption capacities, viscosity, gelation capacity and emulsion properties of infested cowpea varieties were compared with those of uninfested cowpeas. Effects of infestation on nitrogen solubulity and on the protein fractions were also determined. lnfestation depleted the protein, starch and soluble sugar contents of cowpeas. Oil and water absorption capacities were increased while emulsification, foam and viscosity properties were reduced. The nitrogen solubility pattern was altered. Uninfested Kano-white cowpeas (UKW) possessed better foam properties than uninfested Ife-brown cowpeas (UFB). On the other hand, UFB had better emulsification properties than UKW.     

Fractionated Extracts From Gnidia kraussiana (Malvales: Thymeleaceae) as Bioactive Phytochemicals for Effective Management of Callosobruchus maculatus (Coleoptera: Chrysomelidae) in Stored Vigna unguiculata (Fabales: Fabaceae) Seeds

One of the most important global problems is protecting food from insect pests. The negative effects of synthetic insecticides on human health led to a resurgence of interest in botanical insecticides due to their minimal ecological side effects. Therefore, the insecticidal potential of hexane, acetone, and methanol extracts of Gnidia kraussiana Meisn roots at 1 and 5g/kg, and neem seed oil (NSO), used as standard insecticide, were evaluated. Ovicidal and larvicidal toxicity was tested by treating freshly laid eggs and larvae at different immature stages of Callosobruchus maculatus (F.). Cowpea (Vigna unguiculata) (L.) Walp seed damage and weight loss were assessed after a storage period of 4 mo. Repellency effects were detected in choice test using a linear olfactometer. All the fractions were toxic to C. maculatus; however, their bioactivities were inversely correlated with products polarity. Extracts proved to be more toxic than the commercial NSO. The acetone extract was more effective against immature stages of C. maculatus than the methanol extract; eggs, first-, and second-instar larvae being the more susceptible. No cowpea seed damage and weight loss were recorded from the seeds treated with hexane and acetone extracts at the dosage of 5 g/kg, after 4 mo of storage. Extracts evoked stronger repellency effects compared with the tested standard insecticide. According to the above, hexane and acetone extracts are good candidates for incorporation in integrated pest management programs for the control of C. maculatus in stored cowpea seeds.     

影响丹东地区水稻产量水平的因素及解决对策

土壤肥力降低,渗透性差;水稻生育时期降雨偏多,低温寡照;品种抗性不足,品种多乱杂;病虫鼠害严重等因素限制了丹东地区水稻产量的提高。针对影响丹东地区水稻农业生产的限制性因子,提出增加农业投入;改良土壤,培肥地力;改革品种布局;综合防治病虫鼠害;加强新品种的引进和开发等相应对策,以提高水稻产量。     

Disease and pest resistance in grains of sorghum and millets

In this review available information on the mechanisms of resistance to insect pests and fungal pathogens in sorghum and millets is discussed. The primary source of resistance lies in the chemical and physical make up of the grain. Phenolic compounds such as ferulic acid and tannins present in some sorghums are potent inhibitors of pests and pathogens. Grain hardness is a major deterrent to infection and infestation in low tannin grains. The prolamins, the grain storage proteins of sorghum, are organized into protein bodies and provide a physical and a nutritional barrier since they are resistant to digestion by insect and fungal proteases. A plethora of proteins that belong to the ‘pathogenesis related protein’ group are distributed in various parts of the grain. Some of them are located in protein bodies. Notwithstanding, sorghum is still susceptible to insect pests and fungal pathogens. An understanding of the natural mechanisms of resistance in the grain is paramount for the development of durable resistance against pests and pathogens. The pyramiding of resistance genes and the development of transgenic lines based on this understanding are two sources of hope for the future protection of sorghum and millets.     

The Bio-Functional Properties of Pigmented Cereals may Involve Synergies among Different Bioactive Species

This study was aimed at characterizing the anthocyanins and phenolics profile in different varieties of pigmented corn and wheat and in some of their milling fractions. Acid/ethanol extracts were used to assess total anthocyanins, overall antioxidant activity, the overall polyphenol profile, and for evaluating the inhibition of pancreatic α-amylase and of intestinal α-glucosidase. Both enzymes were inhibited in a dose-dependent manner by all extracts, but individual extracts had specific effects on each enzyme. Anti-inflammatory response was evaluated by using acid-free extracts and Caco-2 cells transiently transfected with a luciferase reporter gene responding to cytokine stimulation. The immune response of interleukin-stimulated cells decreased significantly in a dose-dependent manner in the presence of 20–50 μM/l anthocyanins from all grains extracts, again with a different efficiency. The inhibitory ability and the anti-inflammatory capability of these extracts are in most cases higher than in similar extracts from other sources, suggesting that activities in each extract may imply specific synergies between anthocyanins and other phenolics.

     

Effects of an insect–nematode–fungus pest complex on grain yield and composition of specialty low linolenic acid soybean

Linolenic acid is a precursor to components in plant defense responses to pests and pathogens. Soybean cultivars with altered seed linolenic acid contents have been developed for improved oil qualities, specifically reduced fatty acid content with increased stability. We examined how three common soybean pests, the soybean cyst nematode (SCN, Heterodera glycines), brown stem rot (BSR) caused by Cadophora gregata and the soybean aphid (SBA; Aphis glycines), affect yield and seed linolenic acid percentage of low linolenic acid cultivars. In a micro-plot field experiment, soybean cultivars with varying concentrations of linolenic acid in the seed (ultra-low or low) and resistance to SCN (susceptible or resistant) were grown at a central Iowa research farm. Plots were kept free of pests (control) or artificially infested with a single pest (SCN, BSR or SBA) or the combination of all three pests (multiple pest). The use of resistant cultivars (SCN and BSR) or an insecticide at an economic threshold (SBA) was analyzed to determine the efficacy of current management recommendations for low linolenic acid soybean production. Seed was collected at the end of the season to measure yield and grain composition. All three pests alone or in combination were capable of reducing yield, but only the three pests in combination were capable of affecting seed linolenic acid percentages, increasing linolenic acid percentages by 11.7% in SCN-susceptible cultivars. For all three pests, current management recommendations (resistant cultivars or economic thresholds) provided protection of both yield and grain composition, indicating no changes in management are necessary for altered linolenic acid soybean cultivars.     

中国杂交稻的"超感虫性"研究概况

介绍了高度感虫的中国杂交稻推广带来水稻害虫生态地位发生的变化.褐飞虱和白背飞虱上升为杂交稻上最突出的极易爆发成灾的重要害虫.20世纪70年代以前,白背飞虱只是水稻上的次要害虫,但80年代以来其种群大大增加.由于它从中国南部杂交稻种植区大范围迁飞,白背飞虱也成为中国中部地区粳稻上的重要害虫.由于种植具有抗褐飞虱基因Bph1的杂交稻组合,褐飞虱种群曾得到暂时的控制.然而,抗虫性的杂交稻在中国中部和南部稻飞虱迁飞区推广以后,褐飞虱生物型发生了改变,对抗虫品种产生了适应性.1990年以后,以前表现抗虫的杂交稻变得高感褐飞虱.缺乏抗虫性主基因不是中国杂交稻对稻飞虱超感性的充分理由,杂交稻旺盛生长的杂种优势可能是稻飞虱生殖力提高的部分原因.中国杂交稻对稻飞虱的超感虫性是从不育系遗传而来的.因此,杂交稻抗虫性的提高有赖于不育系的改良.利用持久抗性和多抗性的IR品种如IR64作为恢复系是改善中国杂交稻的超感虫性的一种有效方法.杂交稻上二化螟和三化螟为害也有所增加.与常规稻相比,杂交稻是一种更有利的食料植物且耐虫性更强.进行水稻产量损失的估计,尤其是水稻本身对螟虫为害的补偿能力,以及螟虫和杂交稻之间的生态学关系的研究有助于评价杂交稻对螟虫田间抗性的实际影响.     

Screening of the susceptibility of newly released genotypes of potato to thrips infestation under field conditions in northwest Iran

Use of host plant resistance is an essential component of integrated management of Thrips tabaci Lindeman. The present research was designed to screen five commercial cultivars of potato, namely Agria, Kondor, Morene, Diamant and Savalan, and two breeding lines 397082-2 and Khavaran for their susceptibility to thrips infestation and for their mean relative plant growth rate (MRGR) and crop yield in an experimental field (not frected with insecticides) and a control field (chlorpyrifos frected) in the Ardabil region of Iran in 2011 and 2012. Thrips populations were assessed by visual inspection on potato leaves. At harvest time, the percentage of leaf area damaged by thrips infestation was assessed on leaves of the tested genotypes. All adults of phytophagous thrips collected in the experimental field were T. tabaci. In both years the mean numbers of thrips adults and larvae were lowest on Savalan cultivar among the tested genotypes. The mean damage index was also lowest on Savalan in both years and the MRGR and the mean yield were greatest in Savalan in the control field. Moreover, in thrips-infested plants, the lowest percentage of MRGR loss and the lowest percentage of yield reduction were observed in Savalan (3.7% and 5.8%, respectively). Of the genotypes tested, Savalan is the most resistant host and has potential for use in the sustainable management of T. tabaci on potato.     

Movento, an innovative ambimobile insecticide for sucking insect pest control in agriculture: Biological profile and field performance

The tetramic acid derivative spirotetramat (brand name Movento^®), has shown an outstanding performance against sucking insect pests in laboratory and greenhouse assays as well as in semi-field and field trials. The product acts as an inhibitor of lipid biosynthesis and affects juvenile stages with additional effects on adult fecundity. There is no cross-resistance to any other insecticide. After foliar application spirotetramat penetrates through the leaf cuticle and is translocated as spirotetramat-enol via xylem and phloem, up to growing shoots and down to roots. This full ambimobility or two-way systemicity (phloem and xylem transport) ensures the control of hidden and soil living sucking pests after foliar application and protects new shoots. The worldwide field development of spirotetramat in Bayer CropScience AG resulted in numerous uses against many species of whiteflies, aphids, scales (soft and armoured scales), mealy bugs, psyllids and selected thrips species in vegetables, cotton, soybean, pome and stone fruit, grapes, hop, citrus, nut trees and banana. The new mode of action renders spirotetramat as an excellent rotation partner with existing products for the management of aphid, whitefly and psyllid populations, which are frequently resistant to conventional insecticides. Moreover, only low adverse effects have been found on beneficial arthropods, which make the product suitable for modern integrated pest management (IPM) systems. These unique properties contribute to safeguarding the crop yield potential both in quality and quantity. In this paper, the new chemistry is presented, compared with standard insecticides and novel applications in IPM systems are discussed.     

The effect of combined infestation by cereal aphids (Macrosiphum avenae (Fabr.) (Sitobion avenae) and Rhopalosiphum padi (L.)) and cereal leaf beetles (Oulema melanopus (L.)) on their population development and on yield of winter wheat

Previous clarification of the relationships between insect populations and damage by cereal pests has enabled the effect of combined pest infestation on the yield of winter wheat to be analysed more thoroughly. The cereal aphids Macrosiphum avenae (Fabr.) (Sitobion avenae) and Rhopalosiphum padi (L.), each in combination with the cereal leaf beetle Oulema melanopus (L.), were investigated in pot trials which enabled interactions between the combined pest populations to be studied also. Although intraspecific competition was observed for each pest population, there was no interspecific adverse effect of density on population increase. With increasing population densities of the pests in combination, the relative contribution of each species to the combined yield losses decreased. Consequently, there was no summation of individual losses, but a reduction of up to 24·3%. The ability of the cereal plant to compensate for losses may be responsible for this ‘buffering effect’, which apparently is attributable to increased dry-matter production in the presence of large combined pest populations. These results suggest that the existing economic thresholds relating to the effects of cereal aphids and cereal leaf beetle on yields of winter wheat require modification.     

秸秆还田对水稻病虫害及产量影响研究

试验研究了秸秆还田对水稻病虫害发生的影响。结果表明,秸秆还田对水稻有一定的增产作用,但同时秸秆还田也会加重水稻病虫害的危害程度,生产上需综合考虑秸秆还田数量、年限、种植品种等因素,以达到增产同时不加重病害发生。