Septoria Leaf Spot Research Articles

Influence of Spore Density, Leaf Age, Temperature, and Dew Periods on Septoria Leaf Spot of Tomato

In order to determine the effects of spore density, leaf age, dew period, and temperature on the susceptibility of tomato to Septoria lycopersici, growth chamber studies were conducted. Depending on the leaf area, 3-5 ml of water containing 10 2 , 10 3 , 10 4 , 10 5 , and 10 6 spores per milliliter were brushed onto the third true leaf up to the seventh true leaf. The log of the disease severity (lesions per square centimeter of leaf) was linearly correlated with the log of the inoculum density (spores per square centimeter of leaf). Older leaves were more susceptible than younger leaves to Septoria leaf spot when inoculum densities were high (10 4 spores per square centimeter of leaf), but younger and older leaves were uniformly susceptible when inoculum densities were low (10 1 to 10 2 spores per square centimeter of leaf). When older leaves were brush inoculated (104 spores per square centimeter of leaf), the number of lesions that developed was highest at temperatures between 20 and 25 C, but lesions still developed at 10 C. When brush-inoculated leaves were incubated for 10 days at 50-6O% relative humidity without any dew period, the number of lesions that developed did not significantly differ from inoculated leaves that had received 16 hr of dew. Disease severity increased when the dew period extended beyond 20 hr. When leaves were spray inoculated, no lesions developed when dew was absent, but lesions did develop on leaves that were given 24 hr of dew. Our findings suggested that a low incidence of Septoria leaf spot may develop under unfavorable conditions and that leaf abrasion may allow spores to infect in the absence of dew

Influence of Rain Events on Spatial Distribution of Septoria Leaf Spot of Tomato

Tomato seedlings spaced 30 cm apart were placed 30-180 cm from an inoculum source in the field for 24-hr periods on five rain dates and five non-rain dates. The mean number of lesions per leaf on plants exposed on rain dates ranged from 70 to 1,680, whereas only 0.0-0.46 lesions per leaf developed on plants exposed on non-rain dates. The mean number of lesions per leaf was linearly related to millimeters of rainfall during exposure periods (b 0 = −224, b 1 = 528, R 2 = 0.86, P < 0.0001). Percent defoliation within rows of tomato plants increased at the apparent infection rate of 0.282 units per day following spray inoculation of the center plant in each row. The study confirms that rain is a primary mechanism for spore dissemination and an important factor contributing to the development of Septoria leaf spot epidemics in tomatoes

An Epidemic of Septoria Leaf Spot onPopulus trichocarpain the Pacific Northwest in 1993

An Epidemic of Septoria Leaf Spot on<i>Populus trichocarpa</i>in the Pacific Northwest in 1993

Septoria Leaf Spot of Lantana from Ecuador: A Potential Biological Control for Bush Lantana in Forests of Hawaii

Pathogenicity tests with a Septoria sp. isolated from Lantana camara from Ecuador showed aggressiveness to four L camara selections from Hawaii forests. The initial symptoms of the disease on inoculated leaves were chlorotic spots that appear within 2 weeks, becoming distinctly angular necrotic lesions in 4 weeks, inducing leaf chlorosis and defoliation 6 weeks after inoculation. Inoculum applied at 1 x 10 6 conidia per ml in 2% sucrose-0.5% gelatin solution produced an average of 87 lesions per leaf. Ornamental hybrids of L. camara x L. montevidensis also were susceptible, but these plants had significantly fewer lesions. All selections of L. montevidensis tested were immune. This Septoria sp. from Ecuador is the first pathogen found to be virulent on bush lantana, the most serious ecological threat to Kauai's forest, and its release is presumed to be an effective biocontrol agent for this weed.

CONTROL OF SEPTORIA LEAF SPOT OF PISTACHIO (PISTACIA VERA)

Studies were established in 1992 and 1993 in a mature commercial pistachio orchard to determine the effectiveness of several fungicides for control of septoria leaf spot (Septoria pistaciurum). Fungicide treatments used in 1992 were Bravo 720F at 3.0 lbs./A (ai.) and 4.5 lbs./A a.i.; Kocide 101 50W at 8.0 lbs./A a.i. plus Benlate 50W at 1.0 lb./A a.i. Fungicide treatments in 1993 were Bravo 825 WDG at 3.0 and 4.5 lbs./A a.i. and Benlate 50W at 2.0 lbs./A a.i. Treatment replications consisted of two treated trees separated by nontreated trees within the row and nontreated tree rows dividing treated rows. At crop maturity, disease severity was determined by counting the number of leaf spots caused by septoria on ten leaves collected at random from each of the two trees of each replicated plot. All treatments significantly reduced disease severity compared to trees receiving no fungicide treatments. Experimental plots were too small to detect any apparent effect of fungicide treatments on yield. Leaves around nut clusters not receiving fungicide treatments were senescent at crop maturity, while leaves on treated trees showed no sign of senescence.

Population-dependent selection strategies needed for 2-year-old black cottonwood clones

We conducted a study to determine whether genotypic and phenotypic covariances among important traits differed between collections of black cottonwood (Populustrichocarpa Torn &amp; Gray) from British Columbia and northern Idaho. We also determined how differences in estimated covariances could affect various multiple-trait clonal selection strategies. The experimental design consisted of 166 clones from British Columbia and northern Idaho intermixed at random in two replications of three-tree row plots. Measurements made during the second growing season included tree height, frequency and number of sylleptic branches, number of leaves, and the lengths and areas of leaf plastochron index 5, 10, and 15 leaves at the end of the growing season. The severity and extent of Melampsora leaf rust and Septoria leaf spot were also evaluated. We found high heritability for tree height, phenology, leaf morphology, and resistance to damaging agents. However, no advantage to using leaf morphology to improve genetic selection for tree height was demonstrable. Restricted selection indices had high potential utility for controlling increases in damaging agents. However, the relation between tree height and leaf diseases varied between the British Columbia and northern Idaho collections of black cottonwood, and between black cottonwood and an adjacent experimental population of balsam poplar (Populusbalsamifera L.). Such population-related variation in intertrait covariances suggests that selection strategies involving disease resistance may need to be evaluated on an individual population basis.

799 PB 077 SUSCEPTIBILITY OF AMERICAN, EUROPEAN, AND INTERSPECIFIC HYBRID GRAPE CULTIVARS TO THE FUNGUS SEPTORIA AMPELINA

European Vitis vinifera L. (four cultivars); interspecific hybrid (seven cultivars); and American V. aestivalis Michx. (one cultivar), V. labrusca L. (three cultivars), and V. rotundifolia Michx. (two cultivars) grapevines were tested for susceptibility to Septoria leaf spot disease. V. rotundifolia cultivars Cowart and Fry exhibited hypersensitive-type resistance. All other American, European, and hybrid cultivars tested were susceptible with varying levels of disease severity. Cultivars with little (e.g. interspecific hybrid) or no (e.g. European) V. labrusca L. heritage were more susceptible to Septoria leaf spot than American V. labrusca cultivars.

Influence of regeneration method and tissue source on the frequency of somatic variation in Populus to infection by Septoria musiva

Septoria leaf spot and canker are serious diseases of many hybrid poplar clones in plantations established for biomass production. Developing resistant clones through breeding is the best long-term strategy to minimize tree damage caused by this disease. Tissue culture and somaclonal selection techniques may reduce the time needed to develop disease resistance in poplars. We used a single source clone of a hybrid Populus to determine the influences of explant tissue source and regeneration method on the frequency of somatic variation in disease resistance. Plants were regenerated adventitiously via shoots and somatic embryos from callus derived from several tissue sources and from axillary buds. The resulting plants expressed somatic variation in disease resistance in different frequencies, except for the plants regenerated from hardwood cuttings. Several regenerated plants from various tissue sources exhibited variant morphological phenotypes, providing further evidence of the instability of this clone when cultured in vitro. Although mutagenic effects of the culture regimes alone cannot be ruled out, results of this study suggest that the explant source and culture method influenced how frequently variant plants were recovered.

Septoria Leaf Spot, a Potential Biological Control for Banana Poka Vine in Forests of Hawaii

Septoria Leaf Spot, a Potential Biological Control for Banana Poka Vine in Forests of Hawaii

Susceptibility of American, European, and Interspecific Hybrid Grape Cultivars to the Fungus Septoria ampelina

European Vitis vinifera L. (four cultivars); interspecific hybrid (seven cultivars); and American V. aestivalis Michx. (one cultivar), V. labrusca L. (three cultivars), and V. rotundifolia Michx. (two cultivars) grapevines were tested for susceptibility to septoria leaf spot disease. V. rotundifolia cultivars Cowart and Fry exhibited hypersensitive-type resistance. All other American, European, and hybrid cultivars tested were susceptible with varying levels of disease severity. Cultivars with little (e.g., interspecific hybrid) or no (e.g., European) V. labrusca L. heritage were more susceptible to septoria leaf spot than American V. labrusca cultivars.

Use of selection indices to increase tree height and to control damaging agents in 2-year-old balsam poplar

Cuttings were collected from balsam poplars (Populusbalsamifera L.) representing 21 populations in Minnesota, Wisconsin, and Michigan, and a replicated nursery trial containing 153 clones was established. Tree height, phenology, leaf morphology, and resistance to damaging agents were evaluated during the second growing season, and genetic and phenotypic variances and covariances among traits were estimated. Clones differed significantly in all traits. However, populations differed only in tree height, number of leaves produced after August 31, bud-set date, number of sylleptic branches (i.e., branches that arise from buds the same year that the buds formed), and severity of Septoria leaf spot symptoms. Tree height was positively correlated with number of leaves, bud-set date, most measures of leaf size, and resistance to Melampsora leaf rust. Predicted responses to index selection for 2nd-year tree height using leaf area or leaf length as secondary selection criteria were not significantly greater than predicted response to univariate selection for tree height alone. However, results supported use of restricted selection indices to curb increased susceptibility to damaging agents that would otherwise result from selection for tree height.

Reduction in Tomato Yield Due to Septoria Leaf Spot

Reduction in Tomato Yield Due to Septoria Leaf Spot

Damage by Septoria leaf-spot on 3 species of Betula in the nursery

Damage by Septoria leaf-spot on 3 species of Betula in the nursery

EFFECT OF LATE-SEASON FUNGICIDE APPLICATION ON GRAIN YIELD AND SEED SIZE DISTRIBUTION IN WHEAT AND BARLEY

Field trials were conducted to determine the effect of foliar fungicides on grain yield, kernel size and seed size distribution in wheat and barley. Tilt (propiconazole) was applied at 125 g a.i. ha−1 between Zadoks growth stages 49 and 59. Following harvest, seed samples from treated and untreated plots were stratified into different size classes. In barley trials, net blotch was the most prevalent leaf disease while in wheat trials, tan spot, leaf rust and Septoria leaf spot were most prevalent. Under high levels of disease, Tilt reduced the level of disease and significantly increased grain yield and the amount of large kernels in both wheat and barley. Under low levels of disease, Tilt rarely increased grain yield, but frequently increased the amount of large kernels. In barley, the increase in amount of seed in the larger size classes across all sites was correlated (P &lt; 0.05) with reduction in net blotch severity. No significant effect of Tilt on germination at 5 °C was observed for any of the wheat cultivars considered in this study. Increases in the yield of large kernels indicate that late season applications of fungicide may be useful in pedigreed seed production, where large kernels are desired.Key words: Seed crops, kernel weight, seed vigor, tan spot, Septoria, net blotch

Septoria Leaf Spot on Dogwoods

The fungus that frequently defoliates Siberian and yellow-twig dogwoods is identified as Septoria cornicola. Pathogenicity was confirmed in artificial inoculation trials, and environmental influences on fungal growth, sporulation, and spore germination were established.

First Report of Septoria Leaf Spot of Pistachio in Arizona.

First Report of Septoria Leaf Spot of Pistachio in Arizona.

Effect of Herbicides and Oat Amendment on Soybean Disease Development and Seed Quality

AbstractThe effects of four herbicides and hand weeding and no weeding on soybean disease development and seed quality were studied in the field. Chloramben, dinoseb, fluchloralin, and trifluralin were preplant incorporated at recommended rates. In addition, the effect of an in‐furrow oat (Avena sativa L.) amendment used as an inoculum carrier was studied in all treatments. Compared with the hand‐weeded control, yield, incidence of Septoria leafspot (Septoria glycines), and the recovery of Phomopsis spp. from pod and stem tissues were reduced in the week‐infested control and dinosebtreated plots. Recovery of Alternaria spp. was greater from crown tissues of plants grown in chloramben‐ and fluchloralin‐treated plots compared with, either the weed‐infested or hand‐weeded control. Septoria leafspot ratings and recovery of Phomopsis spp. from various plant tissues were higher in plants from hand‐weeded plots compared with weed‐infested plots, whereas the opposite was truefor, the recovery of Fusarium spp. Chloramben‐treated plots were high‐yielding and had the best weed control of all herbicide treatments. Seed quality was not affected by herbicide treatment. Plants from furrows with autoclaved oats had a lower incidence of Septoria glycines, a greater recovery of Fusarium spp. from pod and stem pieces, and produced seed with lower quality than plants from rows with no oat amendment.

Cultivation and breeding of Digitalis lanata in the Netherlands.

After the second world war Marshall Aid funds were used to establish a cooperative organisation for growing, drying, and selling Digitalis lanata (and other medicinal, aromatic, and culinary herbs) in the Netherlands. The crop is sown in mid April and the fully mechanised harvest of the leaves takes place from September to late November. The leaves are dried for 10-12 hours at 50 degrees C maximum. The aim of breeding trials is to improve leaf production, erect leaf attitude, resistance to Septoria leaf spot and to bolting, and a higher dry matter and digoxin content.

Control of an Epidemic of Septoria Leaf Spot of Tomato by Resistance

Control of an Epidemic of Septoria Leaf Spot of Tomato by Resistance

Epidemiology and assessment of importance of septoria leaf spot

Epidemiology and assessment of importance of septoria leaf spot