Infestation Of Wheat Research Articles

Biological control of broad-leaved dock infestation in wheat using plant antagonistic bacteria under field conditions.

Conventional weed management systems have produced many harmful effects on weed ecology, human health and environment. Biological control of invasive weeds may be helpful to minimize these harmful effects and economic losses incurred to crops by weeds. In our earlier studies, plant antagonistic bacteria were obtained after screening a large number of rhizobacteria for production of phytotoxic substances and effects on wheat and its associated weeds under laboratory conditions. In this study, five efficient strains inhibitory to broad-leaved dock and non-inhibitory to wheat were selected and applied to broad-leaved dock co-seeded with wheat both in pot trial and chronically infested field trial. Effects of plant antagonistic bacteria on the weed and infested wheat were studied at tillering, booting and harvesting stage of wheat. The applied strains significantly inhibited the germination and growth of the weed to variable extent. Similarly, variable recovery in losses of grain and straw yield of infested wheat from 11.6 to 68 and 13 to 72.6% was obtained in pot trial while from 17.3 to 62.9 and 22.4 to 71.3% was obtained in field trial, respectively. Effects of plant antagonistic bacteria were also evident from the improvement in physiology and nutrient contents of infested wheat. This study suggests the use of these plant antagonistic bacteria to biologically control infestation of broad-leaved dock in wheat under field conditions.

Green Manure Comparison between Winter Wheat and Corn: Weeds, Yields, and Economics

Red clover (Trifolium pratense L.) and hairy vetch (Vicia villosa Roth) are leguminous crops (“green manure” hereafter), widely studied for their N2‐fixing contributions to cropping systems. Under certain circumstances they can provide weed control in cash crops. This study compared weed control, crop yields, herbicide use, and economic performance of these green manures in a no‐till winter cereal–green manure–corn (Zea mays L.) silage cropping sequence in central Pennsylvania. Red clover was interseeded into winter wheat (Triticum aestivum L.) or rye (Secale cereale L.), while hairy vetch and triticale (X Triticosecale) were planted after winter cereal harvest. Compared to hairy vetch, red clover provided continuous soil cover between the winter cereal and corn and two herbicide applications could not be applied (one in wheat and one prior to seeding hairy vetch) to the red clover, reducing herbicide active ingredient use by 28%. Weed infestation in wheat and corn did not differ between green manure systems, but corn yield following red clover averaged 3320 kg ha−1more, and 2012 wheat yield was 180 kg ha−1 greater in the red clover sequence. Corn after hairy vetch–triticale had lower corn plant population in 2012–2013. Yield differences in corn in 2012 probably resulted from population differences. Primarily because of red clover forage value, the red clover system resulted in greater net returns to management by US$1360 ha−1, and even without the forage harvest, the red clover system would have been more profitable due to lower production costs.Core Ideas As a green manure, red clover provided multiple benefits over hairy vetch and triticale. Red clover underseeded in winter grain, produced continuous cover, forage, and higher corn yield. Compared to hairy vetch and triticale, red clover controlled weeds with less herbicide. Red clover was more profitable than hairy vetch.

Life Cycle and Digestive Physiology ofTrogoderma granarium(Coleoptera: Dermestidae) on Various Wheat Cultivars

The Khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae), is known as one of the world's most damaging pests of wheat and other stored products. The life cycle, nutritional indices, and digestive enzymatic activity of T. granarium in response to feeding on six wheat cultivars (Arg, Morvarid, Nai 60, Parsi, Pishtaz, and Shanghai) were evaluated under laboratory conditions (33 ± 1°C, 65 ± 5% relative humidity, and a photoperiod of 14:10 [L:D] h). In this research, delayed developmental time of T. granarium immature stages was detected on cultivars Parsi and Morvarid. The highest survival rate of immature stages was on cultivar Arg, and the lowest was on cultivars Morvarid and Parsi. Moreover, the highest mean larval weight and weight gain of larvae were on cultivar Arg, while the lowest ones were on cultivars Parsi and Morvarid. In addition, the lowest values of relative growth rate and proteolytic activity were detected when larvae were fed with cultivars Morvarid and Parsi. Based on the obtained results, it can be concluded that cultivars Parsi and Morvarid were the most unsuitable cultivars for the development and feeding of T. granarium . The resistant cultivars can be recommended to be grown in areas where the damage of T. granarium is high for protecting or at least delaying wheat infestation by this pest.

Effect of salicylic acid on winter wheat infestation by fungal diseasesWpływ kwasu salicylowego na porażenie pszenicy ozimej przez patogeny grzybowe

A field experiment was carried out in 2011–2013 to evaluate the effect of foliar application of UPP-208 200 SL formulation containing salicylic acid (SA; 200 g/l) and surface acting agents on infestation of fungal diseases occurring in winter wheat. Wheat plants were treated with a single spray of UPP-208 200 SL at a growth stage of BBCH 26 or BBCH 32 and the split doses of 0.5, 1.0 and 2.0 l/ha applied at BBCH 26 and BBCH 32. Salicylic acid partially decreased wheat infestation by Blumeria graminis, Mycosphaerella graminicola and Pyrenophora tritici-repentis. However, the level of disease control varied according to the experimental year, salicylic acid application time and rate. Generally, the use of split applications of salicylic acid resulted in a better protection against wheat diseases than the use of single applications.

Efficient detection of internal infestation in wheat based on biophotonics

In the process of grain storage, there are many losses of grain quantity and quality for the sake of insects. As a result, it is necessary to find a rapid and economical method for detecting insects in the grain. The paper innovatively proposes a model of detecting internal infestation in wheat by combining pattern recognition and BioPhoton Analytical Technology (BPAT). In this model, the spontaneous ultraweak photons emitted from normal and insect-contaminated wheat are firstly measured respectively. Then, position, distribution and morphological characteristics can be extracted from the measuring data to construct wheat feature vector. Backpropagation (BP) neural network based on genetic algorithm is employed to take decision on whether wheat kernel has contaminated by insects. The experimental results show that the proposed model can differentiate the normal wheat from the insect-contaminated one at an average accuracy of 95%. The model can also offer a novel thought for detecting internal infestation in the wheat.

CEREALS ASSESSMENT TOWARDS CONTAMINATION OF PHYTOPATHOGENIC FUNGI IN FOREST-STEPPE AREA OF UKRAINE

The usage of high-quality seed, not affected by pathogens and fungi promote the high and stable yields. The condition of seeds determines their germination, seedling damage and adult plants, which ultimately affects the yield and on their quality. The significant risk of seed infection was registered in years with high humidity in the pre-harvest and harvest period. Therefore, along with the traditional seed control it is necessary to conduct phytopahtology expertise, allowing to identify the species composition of the microflora of seeds and the degree of infection with different pathogens. Smut disease - a solid and loose smut of wheat, hard and loose smut of barley - cause crop losses are clear - in the form of the destruction of the ear, and hidden - in the form of a reduction in seed germination, reduce winter hardiness, plant growth inhibition. Pathogens root rot causing blight, Fusarium and Helminthosporium that insignificantly demand on environmental conditions and extremely plastic. They have large set of enzymes that can exist on a variety of substrates, and therefore are widely distributed in nature and cause considerable damage to crops. Especially significant losses occur if the humidity during the ripening grain observed for several seasons, which leads to accumulation of the infection naturally. The aim of research was to assess the contamination of grain of spring wheat and barley phytopathogenic fungi in one of the main grain regions of Ukraine - the southern forest. The research conducted during the summer 2014 and compared with the results of previous years. Samples were taken from different plots. Seed contamination of samples by various phytopathogenic fungi was determined by the number of infected kernels per 100 seed sample. Frequency of registered species was recorded. For every studied sample we set the percentage of species. Analysis of the grain on the fungal infection and avdelenie in pure culture was performed according to the procedures used a method of washing and centrifugation, seeds, embryos analysis method, biological method based on the stimulation of development and growth of pathogens in the infected seeds during seed germination in nutrient media. We analyzed 200 samples of wheat and barley grain with 8 games on the definition of the infestation and root rot spores solid and smut. In all the samples studied was dominated latent form of infection grains (outwardly healthy, germinating, well executed seeds had normal luster, patina fungus was absent); but sometimes observed apparent lesion (plaque formation, a different degree of deformation of grains). When the microscope isolated fungi was established dominance of species such as fungi of the genera Alternaria, Helmintosporium, Fusarium, smut fungi. The research of cereal seeds showed that all the tested party for the harvest in 2014 were infected with different pathogens in different degrees. On the basis of literature data and our own observations, comparing infection rates average cereal seeds complex fungal diseases, it may be noted that in 2014 the percentage of infestation was higher than in previous years, there is a trend of growth in incidence. The results showed that the overall percentage of infected root rots seeds of spring wheat in 2014 was 55.5 %, the infestation of spring barley was 64.7 %. Compared to previous years the trend increase in the prevalence of fungal diseases on cereals: wheat infestation grew by 12.8 %, barley - 2.13 %. Smut infected - 11.2 % wheat, barley - 37.4 %. Infection bunt was 4.6 %, including 3.3 % of wheat; Barley 17.6 %. The growth and development of root rot during the growing season depended on the presence of soil infection. Infection of grain crops by smut diseases depend on the quality of seed sown. Reducing the prevalence of smut disease is possible at early winter and late spring sowing to prevent the spore germination at low temperature. Keywords: seeds, disease, infection, agents of fungal diseases, spores.

Effect of Sowing Date and Cultivars on Aphid Infestation in Wheat with Climate Change Adaptation Perspective

Four field experiments, two experiments each during winter season of 2012–2013 and 2013–2014, were conducted to evaluate effect of sowing time and four wheat cultivars on population of wheat aphids. Wheat crop was found infested with Rhopalosiphum padi and Sitobion avenae in various proportions in different experiments. During vegetative crop phase, December (late) sown crop had in general higher aphid population than November (timely) sown crop, while during reproductive crop stage, timely sown crop harboured more aphids on ear heads than late planted one. October (early) and January (very late) sown crop evaded aphid attack on ear heads. Significant differences in peak aphid populations among different plantings indicated that alteration of sowing time might disturb phenological synchrony between aphids and wheat crop, affecting pest population. Aphid population was positively influenced by the temperature. Sowing dates were also found to significantly affect the crop yield. Among varieties, WR-544 was observed to have lower number of aphids than other cultivars during vegetative crop stage. Because alteration in sowing time is deemed to be one of the adaptation strategies to sustain agricultural productivity under climate change, effect of sowing time on aphid population is the need to be heeded while formulating such strategy for effective crop management.

Preliminary study of solid phase micro-extraction (SPME) as a method for detecting insect infestation in wheat grain

In this study, new method was investigated using solid phase microextraction (SPME) for detection of insect infestation in stored wheat. The results show that volatile pheromones isolated from a number of common stored grain insects, can be used to indicate infestation. The amounts of pheromone released varied between species. Rhyzopertha dominica (F.) was the highest volatile pheromone producer among the species investigated, then it was followed by Tribolium castaneum (Herbst), Cryptolestes ferrugineus (Stephens) and Cryptolestes pusillus (Schönherr), respectively. This resulted in different sensitivity when SPME was used for detection. A single specimen of T. castaneum and R. dominica could be successfully detected in 1 kg of wheat, whereas more number of C. ferrugineus and C. pusillus beetles were required for detection in the same quantity of grain.Extraction period and temperature affected the sensitivity of the SPME method. Longer exposure time and higher temperature allowed more analytes to be collected. Consequently, extraction for 4 h at 50 °C appeared to be the optimum condition for extracting pheromones produced by the beetles covered by this study. The method was further adjusted to be more practical and this resulted in changing the sensitivity. Detection of a single R. dominica could still be successfully achieved, even though the time and the temperature were reduced, whereas for the remaining species, the minimum number of insects required had to be increased by about 40–60% in order to detect volatile pheromone in headspace. In conclusion, the SPME technique in detection of infestation is still required further development to be applied to the grain industry. Dynamic headspace may help improve the sensitivity of technique.

Potassium phosphate induces tolerance against the Russian wheat aphid (Diuraphis noxia, Homoptera: Aphididae) in wheat

Diuraphis noxia Kurdjumov is an aphid pest that hampers the global production of wheat (Triticum aestivum L.). Infestation of wheat by D. noxia reduces crop yield and sometimes leads to the death of susceptible cultivars. To date resistant cultivars have been used to control infestations. However, the development of resistance-breaking aphid biotypes is complicating this management strategy. This study aimed to ascertain the effect that 25 mM potassium phosphate (K3PO4) treatment has on inducing resistance in wheat against D. noxia. The effects of potassium phosphate on induced resistance against D. noxia were determined using gene regulation and enzymatic levels of lipoxygenase (EC 1.13.11) and phenylalanine ammonia lyase (EC 4.3.1.24). The results indicated that the treatment of both susceptible (Scheepers) and resistant (Tugela DN) wheat cultivars with potassium phosphate induces genes differentially. A phenotypic study showed delayed development and less severity of symptoms with decreased numbers of aphids feeding on plants treated with potassium phosphate in comparison with untreated plants for both resistant and susceptible cultivars. The results from the gene expression and enzyme activity studies indicated that both of the induced systemic resistance-linked genes were similarly regulated after potassium phosphate treatment. The data strongly support treatment of wheat with potassium phosphate to induce tolerance against D. noxia.

High spectral and spatial resolution hyperspectral imagery for quantifying Russian wheat aphid infestation in wheat using the constrained energy minimization classifier

The effects of insect infestation in agricultural crops are of major ecological and eco- nomic interest because of reduced yield, increased cost of pest control and increased risk of environmental contamination from insecticide application. The Russian wheat aphid (RWA, Diuraphis noxia) is an insect pest that causes damage to wheat (Triticum aestivum L.). We pro- posed that concentrated RWA feeding areas, referred to as hot spots, could be identified and isolated from uninfested areas within a field for site specific aphid management using remotely sensed data. Our objectives were to (1) investigate the reflectance characteristics of infested and uninfested wheat by RWA and (2) evaluate utility of airborne hyperspectral imagery with 1-m spatial resolution for detecting, quantifying, and mapping RWA infested areas in commercial winter wheat fields using the constrained energy minimization classifier. Percent surface reflec- tance from uninfested wheat was lower in the visible and higher in the near infrared portions of the spectrum when compared with RWA-infested wheat. The overall classification accuracies of >89% for damage detection were achieved. These results indicate that hyperspectral imagery can be effectively used for accurate detection and quantification of RWA infestation in wheat for site-specific aphid management. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI. (DOI: 10.1117/1.JRS.8.083661)

Feasibility of the application of electronic nose technology to detect insect infestation in wheat

Wu, J., D.S. Jayas, Q. Zhang, N.D.G. White and R.K. York. 2013. Feasibility of the application of electronic nose technology to detect insect infestation in wheat. Canadian Biosystems Engineering/Le genie des biosystemes au Canada 55: 3.1-3.9. An Alpha MOS FOX3000 electronic nose (e-nose) equipped with 12 metal oxide semiconductor (MOS) sensors was used to evaluate the presence of insects in wheat. Samples of Canada western red spring (CWRS) wheat (cv. AC Barrie) infested with rusty grain beetle (RGB), Cryptolestes ferrugineus (Stephens), and red flour beetle (RFB), Tribolium castaneum (Herbst), were placed in glass jars fitted for the collection of headspace volatiles. Different insect densities (0, 1, 2, 10 and 20 insects/kg) were tested for each insect species in combination with three moisture content levels for wheat (14%, 16%, and 18% wet mass basis). The headspace volatiles from insect-infested or non-infested wheat were sampled and injected into the e-nose. The response of e-nose sensors, in the form of a multi-dimensional matrix, was extracted and interpreted using AlphaSoft V8.0 software. The automated pattern recognition algorithms in the software (Principal Component Analysis, Discriminant Factorial Analysis, and Partial Least Square) were used to evaluate the samples.

Wheat Mds-1 encodes a heat-shock protein and governs susceptibility towards the Hessian fly gall midge

Gall midges induce formation of host nutritive cells and alter plant metabolism to utilize host resources. Here we show that the gene Mayetiola destructor susceptibility-1 on wheat chromosome 3AS encodes a small heat-shock protein and is a major susceptibility gene for infestation of wheat by the gall midge M. destructor, commonly known as the Hessian fly. Transcription of Mayetiola destructor susceptibility-1 and its homoeologs increases upon insect infestation. Ectopic expression of Mayetiola destructor susceptibility-1 or induction by heat shock suppresses resistance of wheat mediated by the resistance gene H13 to Hessian fly. Silencing of Mayetiola destructor susceptibility-1 by RNA interference confers immunity to all Hessian fly biotypes on normally susceptible wheat genotypes. Mayetiola destructor susceptibility-1-silenced plants also show reduced lesion formation due to infection by the powdery mildew fungus Blumeria graminis f. sp. tritici. Modification of susceptibility genes may provide broad and durable sources of resistance to Hessian fly, B. graminis f. sp. tritici, and other pests.

Evaluation of spectral indices and continuous wavelet analysis to quantify aphid infestation in wheat

Wheat aphid, Sitobion avenae F. is one of the most destructive insects infesting winter wheat and appears almost annually in northwest China. Past studies have demonstrated the potential of remote sensing for detecting crop diseases and insect damage. This study aimed to investigate the spectroscopic estimation of leaf aphid density by applying continuous wavelet analysis to the reflectance spectra (350–2 500 nm) of 60 winter wheat leaf samples. Continuous wavelet transform (CWT) was performed on each of the reflectance spectra to generate a wavelet power scalogram compiled as a function of wavelength location and scale of decomposition. Linear regression between the wavelet power and aphid density was to identify wavelet features (coefficients) that might be the most sensitive to aphid density. The results identified five wavelet features between 350 and 2 500 nm that provided strong correlations with leaf aphid density. Spectral indices commonly used to monitor crop stresses were also employed to estimate aphid density. Multivariate linear regression models based on six sensitivity spectral indices or five wavelet features were established to estimate aphid density. The results showed that the model with five wavelet features (R2 = 0.72, RMSE = 16.87) performed better than the model with six sensitivity spectral indices (R2 = 0.56, RMSE = 21.19), suggesting that the spectral features extracted through CWT might potentially reflect aphid density. The results also provided a new method for estimating aphid density using remote sensing.

English

  Weeds are one of the most important factors that impose a great threat to the crop yield. In order to alleviate the weeds infestation in wheat (Triticum aestivum L.), the efficacy of various pre and post-emergence herbicides were tested during Rabi 2009 to 2010 at the Agronomic Research Area, University of Agriculture, Faisalabad, Pakistan. Results promised that clodinafop propargyl at 0.045 kg a.i. ha-1 with maximum weed kill efficiency severely reduced the Avena fatua, Coronopus didymusand Melilotus indica population and dry weights compared with the control. Poor weed control was achieved using isoproturon at 1.5 kg a.i. ha-1, isoproturon + diflufenicon at 0.98 kg a.i. ha-1, fenoxaprop-p-ethyl at 1.00 kg a.i. ha-1, tralkoxydim at 0.5 kg a.i. ha-1  and chlorsulfuron at 0.074 kg a.i. ha-1. Considering total grain and straw yields (4900 kg ha-1); (6600 kg ha-1), post-emergence clodinafop propargyl at 0.045 kg a.i. ha-1causes an excellent increase in wheat yield (51.02%) over control. The highest spikebearing tillers (380.67), number of grains spike-1 (47.28) and 1000-grain weight (49.38 g) were maximum in clodinafop propargyl at 0.045 kg a.i. ha-1 as post-emergence treated plots. Based on the total wheat yield (grain and straw) obtained, isoproturon at 1.5 kg a.i. ha-1, metribuzin + fenoxaprop-p-ethyl at 1.00 + 1.00 kg a.i. ha-1, chlorsulfuron at 0.074 kg a.i. ha-1 seemed someway phytotoxic to crop plants and depressed wheat yield. Hence, maximum net income of Rs. 136997 ha-1 and maximum MRR (%) of 231316.6 was recorded with the use of clodinafop propargyl at 0.045 kg a.i. ha-1 as post applied followed by carfentrazone ethyl (0.015 kg a.i ha-1) with the MRR (%) of 89700.   Key words: Triticum aestivum L., Avena fatua, Coronopus didymus, Melilotus indica, clodinafop propargyl, weed control, herbicides.

Influence of degree of wheat infestation with Fusarium on its technological quality and safety

Climatic conditions prior to wheat harvest 2010 were favorable for the development of field molds. The most important wheat contamination that should be determined is the presence and frequency of grain lots infected with Fusarium. This paper presents the results of content of fusarious kernels found in samples collected from all wheat growing regions of Serbia. Investigations were performed according to the regulations which foresee sensory determination of content of infected kernels. Determined average content of fusarious kernels was 6.01%, varying in range from 0% to 29.65 %. The obtained results, which exceeded the upper limits of permitted contents defined by national and EU regulations, pointed to the need for investigation of presence of Fusarium metabolic products, i.e. mycotoxins (zearalenone (ZEA) and deoxinivalenol (DON)) in wheat. Mycotoxin content was determined in average wheat samples and in wheat samples with increased content of fusarious kernels. Direct enzymatic immunoaffinity test (ELISA) was applied for determination of mycotoxin content. Although high content of fusarious kernels characterizes wheat crop in 2010, the determined quantities of two investigated mycotoxins did not exceed maximal permitted content. Consequences of unfavorable quantity and structure of total impurities in wheat crop in 2010 reflect decreased commercial and technological quality of wheat and point out to the need of necessary wheat safety control.

Aphid Dynamics in Relation to Meteorological Factors and Various Management Practices in Bread Wheat

Aphid Dynamics in Relation to Meteorological Factors and Various Management Practices in Bread WheatThe infestation of aphids in wheat is becoming a serious problem nowadays and it might become a threat to the future wheat crop in Pakistan. With this problem in mind we did a study pertaining to aphid dynamics in relation to meteorological factors and various management practices in bread wheat. The study was carried out at the Wheat Research Institute, Faisalabad, Pakistan. The aim of this study was to investigate how meteorological factors play a role in the fluctuating aphid population and how different management practices could be effective in combating aphids. The results revealed that a peak aphid population was recorded during the beginning of the third week of March for both of the study year periods of 2007-2008 and 2008-2009. Aphid density was positively associated with maximum as well as minimum temperature while it showed a negative correlation with relative humidity. However aphid population was positively but not significantly affected by rainfall. Early sowing on 1st November produced the least aphid infestation hence early sowing was encouraged as a cultural practice for keeping aphids below damaging levels. The recently developed wheat varieties like: SHAFAQ-06, SEHER-06, FSD-08 and LASANI-08, revealed aphid resistance and performed better against aphids. On the other hand the genotypes V-05003, BARS-09 and 0BT006, revealed maximum vulnerability to aphids. Number of aphids per tiller was positive correlated with loss in grain yield. Application of insecticide significantly controlled the aphid population which suggested that a combination of host plant resistance with chemical control could restrain the aphid infestation in wheat.

Changes in properties of wheat leaf cuticle during interactions with Hessian fly

Infestation of wheat by Hessian fly larvae causes a variety of physical and biochemical modifications of the host plant. Changes occur in cuticle permeability, lipid composition and gene transcript abundance, and these responses differ substantially between resistant and susceptible wheat lines. Staining assays revealed that susceptible plants exhibited a generalized increase in leaf sheath epidermal permeability during infestation; whereas, epidermal permeability was only minimally affected in resistant plants. Furthermore, temporal profiling using gas chromatographic methods revealed that changes in cuticle lipid (wax and cutin) composition correlated well with differing levels of epidermal permeability in susceptible and resistant plants. Temporal analysis of cuticle-associated gene mRNA levels, by quantitative real-time PCR, indicated a relationship between transcript abundance and changes in cuticle lipid profiles of resistant and susceptible plants. Results suggest that conserving cuticle integrity via induction of specific wax constituents and maintenance of cutin amounts, determined by the accumulation of cuticle-associated transcripts, could be important components of wheat resistance to Hessian fly larvae.

Differential levels of mite infestation of wheat and barley in Czech grain stores

Abstract While mites are able to utilize numerous food sources, the suitability of the food strongly influences population growth. The different suitabilities of various stored agricultural products will thus affect the level of infestation. In this study, we compared field mite infestation rates in two stored cereals: wheat and barley. We analyzed mite abundance, frequency and species composition in samples of grain obtained from 79 selected Czech grain stores. Stored barley seemed to be more vulnerable to mite attack than wheat, as we consistently found more infested samples, more species and higher mean and median mite abundance per sample in barley as compared to wheat. The mean mite abundance per sample were 55 and 506 individuals for wheat and barley, respectively. In barley, 10% of samples exceeded allergen risk threshold (i.e., 1 000 individuals per kg of grain). Altogether, 25 species were identified from approximately 35 000 individuals. The most frequently identified species were the same in wheat and barley, that is, Tydeus interruptus Sig Thor, Acarus siro L., Tarsonemus granarius Lindquist, Lepidoglyphus destructor (Schrank) and Tyrophagus putrescentiae (Schrank). Based on principal components analysis, we found a closer association of T. interruptus, T. putrescentiae, L. destructor and Cheyletus eruditus (Schrank) with barley samples, corresponding to the high frequency and abundance values of these mites. The probable reasons for the higher infestation, especially mite abundance in barley, are discussed in relation to the higher proportion of crushed parts, which may release favorable nutrient sources and amplify the abundance values.

Winter wheat infestation after one-year fallow field on the rendzina soil

Winter wheat infestation after one-year fallow field on the rendzina soil

Infestation of Wheat and Downy Brome Grass by Wheat Stem Sawfly and Subsequent Larval Performance

Wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae), oviposition patterns and larval development in downy brome grass, Bromus tectorum L., and wheat, Triticum aestivum L., were compared in a commercially grown wheat field infested with downy brome grass in Montana. Seven weekly randomly selected samples of stems for each plant species were collected at points where both plants were growing together. The level of infestation in downy brome grass was almost two-fold higher than for wheat throughout the growing season. Larval mortality was not detected in either plant species early in the season, but mortality was more frequent in downy brome grass as the host plants matured. Mortality of late-instar larvae late in the season was significantly higher in mature downy brome grass than in mature wheat stems. The weight of these late-instar larvae from wheat was almost four-fold heavier than larvae from downy brome grass. Stem height and seed weight in wheat were significantly reduced by larval sawflies feeding. In contrast, stem height, stem diameter, seed weight, and seed number in grass stems were significantly greater in infested downy brome grass stems compared with uninfested plants. Our results suggest that downy brome grass, a serious weed in wheat cropping, may play an important role in the survival and dynamics of wheat stem sawfly populations in the northern Great Plains.