In this study, surveys were conducted in pea and potato fields in North Dakota and Central Minnesota to investigate the incidence and abundance of plant-parasitic nematodes in these fields. Moreover, the effect of the pin nematode, Paratylenchus nanus, on plant growth and yield of six field pea cultivars was determined under greenhouse conditions. Similarly, the influence of lesion nematode, Pratylenchus penetrans, and wilt fungi, Fusarium oxysporum alone and together on growth and yield of potato cultivar ‘Red Norland’, was evaluated in microplots under field conditions. The results indicate Paratylenchus spp. and Pratylenchus spp. are the most frequent nematodes, respectively, in pea and potato fields. Pin nematodes reproduced on field pea cultivars and caused up to 37% reduction in plant height and 40% reduction in yield. Additionally, both P. penetrans and F. oxysporum alone, and together had significant negative effect on growth and yield of potato.

Cercospora leaf spot (CLS), caused by the fungal pathogen Cercospora beticola, is the most important foliar disease of sugar beet worldwide. Control strategies for CLS rely heavily on fungicides including quinone outside inhibitor (QOI) fungicides. We collected 866 C. beticola isolates from sugar beet growing regions in France and Italy and assessed their sensitivity to the QOI fungicide pyraclostrobin. To gain an understanding of the molecular basis of QOI resistance, we cloned the full-length coding region of Cbcytb. All tested QOI-resistant isolates harbored a point mutation in Cbcytb at nucleotide position 428 that conferred an exchange from glycine to alanine at amino acid position 143 (G143A). A PCR assay was developed to discriminate QOI-sensitive and QOI-resistant isolates based on the G143A mutation. Our results indicate that QOI resistance has developed in some European C. beticola populations in Italy and monitoring the G143A mutation is an essential fungicide resistance management strategy.

Deoxynivalenol (DON), a mycotoxin produced in cereal grains infected by Fusarium Head Blight produced by Fusarium graminearium and Deoxynivalenol-3-β-D-glucopyranoside (DON-3G), were studied during processing using LC-MS-MS and GC. DON reduced significantly (P<0.05) 61.8% during milling into flour. Therefore, DON was concentrated mostly in the bran and germ. DON increased 40.8% during the fermentation stage of baking. DON increased in dough more than flour and mixed dough. Milling reduced by 23.7% but fermentation did not. But bread was significantly lower in DON-3G at 0.15 ppm than flour and dough at 0.31 ppm. The baking increased DON and decreased DON-3G showing a difference in stability of the mycotoxins during processing. Enzyme hydrolysis on DON using α-amylase, cellulase, protease, and xylanase, showed a significant increase with cellulase (20.8%), protease (11.4%), and xylanase (35.6%) compared to wheat composite. DON may be bound to the cell wall or protein component of the kernel.

Predation by thrips was referred to as early as 1882 when Pergande discussed their habits. Later, Plank (1936) found Leptothrips mali (Fitch) to be predaceous on lepidopterous eggs, and Sharp (1938) cited it as a being a predator of the pecan nut caseborer, Acrobasis caryae Grote. Bailey (1939) stated that the six-spotted thrip, Scolothrips sexmaculatus (Pergande), is predaceous on Tetranychus telarius (L.), Tetranychus pacificus McG., Bryobia praetiosa Koch, Paratetranychus citri McG., Paratetranychus pilosus (C & F.), Paratetranychus indicus Hirst, Paratetranychus yothersi (McG.), Paratetranychus ilicis (McG.), and Phyllocoptes oleivorus Aschm. and in 1943 Bailey and Keifer noted that L. mali fed on tomato russet mite, Phyllocoptes desctructor (Keifer). Muma (1955) discussed the predation of S. sexmaculatus, L. mali, and Aleurodothrips fasciapennis (Franklin) on citrus insects and mites in Florida.

Bibliography: pages 175-184. / The occurrence of maize dwarf mosaic virus (MDMV) in field grown maize was investigated. For this purpose, maize showing mosiac symptoms was collected from different maize growing areas in South Africa by Prof. M.B. von Wechmar. These samples from Transvaal, Orange Free State and Natal were then investigated for the presence of MDMV and possible strains of this virus. Three virus isolates were purified and partially characterised. These isolates were serologically compared together with a fourth isolate SCMV 4975, obtained from the U.S., to establish strain relationships.

No description available.

No description available.

Indian ricegrass at the Desert Range Experiment Station forty-seven miles west of Milford, Utah, is damaged by the larvae of Coenchroa illibella, Diatrae sp. and Typoceris ceraticornis, the latter being the most destructive. The biology of the insects and the extent of damage inflicted are discussed. Uninfested plants produced more new stems than infested plants. Plants having a basal diameter of 4 to 6.9 cm and 7 to 9.9 cm were the most frequently infested and, consequently, the most severely damaged.

No description available.

Experiments were conducted at Blacksburg from 1975 to 1978 on soybean, Glycine max (L.) Merrill. The objectives were: (1) to study the inheritance of reaction to peanut mottle virus (PMV); (2) to determine the allelic relationships between genes for resistance from various germplasm sources; and (3) to screen a part of the soybean Plant Introduction germplasm collection and identify PMV-resistant strains. Soybean cultivars, Plant Introduction (PI) strains, and advanced generation progenies derived from selected crosses were artificially inoculated with PMV-S/V74S (a Virginia isolate) and evaluated for their reaction to PMV in the field and greenhouse. Two cultivars, 'Virginia' and 'Pine Dell Perfection', that were previously reported as resistant to a mild PMV strain were found to be susceptible to PMV-S/V74S. Crosses between resistant and susceptible lines and among resistant lines were made in the field in 1976 and 1977. The F₁, F₂, and F₃generation seedlings derived from selected crosses were tested for reaction to PMV in the greenhouse. It was shown that resistance in the cultivar 'Peking' is conditioned by a single recessive gene designated rpv₂. Evidence based on segregation in F₂ populations was also presented that indicates the presence of three other dominant genes for resistance to PMV-S/V74S. The three dominant genes are designated Rpv₁ (first reported by workers in Georgia), Rpv₃, and Rpv₄. Preliminary F₁ and F₂ data were obtained from crosses between 15 resistant PI strains and two resistant "testers," 'York' and PI 89,784. The F₂ data obtained from five crosses indicate the possibility of still other genes for resistance to PMV. The two susceptible lines used in the study, Virginia and PI 229,315, differed markedly in their reactions to PMV. The presence of different alleles or modifying genes controlling the susceptible reactions in the two lines is suggested. A total of 2161 FC and PI strains in Maturity Groups II, III, and IV were inoculated with PMV-S/V74S in the field during 1976 and 1977. Three hundred sixty-six strains that showed 10% or less virus infection were identified. These "resistant" strains provide a pool from which other genes for PMV resistance perhaps can be isolated. Differences in PMV disease reactions of plants from the same strain were noted when plants were tested in both the field and greenhouse. The differences were attributed to the following three factors: (1) differences in stage of plant growth at time of inoculation (field grown plants were generally larger at time of inoculation than plants inoculated in the greenhouse); (2) differences in environmental conditions between the field and greenhouse; and (3) the artist's airbrush inoculation technique was used in the field while the rub inoculation technique (mortar and pestle) was used in the greenhouse. / Ph. D.