Wheat Leaf Diseases and Possibilities of Computer Program Application for Disease Control

The main task of integrated plant protection is to reduce usage of pesticides and to address a request of farmers to cut down variable costs for winter wheat growing (including costs of fungicides). A new tool providing these requirements is a Decision support system based on PC program. Validation trials of PC-P Diseases were carried out in collaboration with Danish Institute of Agricultural Sciences in 1999-2002 in different regions in Latvia. Comparisons were made among standard treatments with full dose of Tango Super (epoxiconazole 84 g l-1, fenpropimorf 250 g l-1) in GS 51-55, split doses in GS 37-39 and GS 51-55 and treatment according to PC-P recommendation. Tan spot (Drechslera tritici-repentis), leaf blotch (Septoria tritici) and mildew (Blumeria graminis) were the most important diseases in this period. The results of trials showed that average doses of fungicide were decreased according to PC-P Diseases recommendations, treatment frequency index fluctuated from 0.2-1.02. Reduced doses of fungicides showed the same efficiency of diseases control as standard doses. Level of additional yield was similar in comparison with variants where standard doses were used

Morphological variability of Botrytis cinerea – causal agent of Japanese quince grey mould

Botrytis cinerea is a causal agent of grey mould that damages many species of plants including Japanese quince (Chaenomeles japonica (Thumb.) Lindley ex Spach). Grey mould has been found on Chaenomeles spp. flowers, fruits in all stages as well as on twigs. Morphological variability within Botrytis species has been previously reported in the literature, but no information is available about B. cinerea isolated from Chaenomeles spp. The aim of this study was to describe the symptoms of grey mould and clarify the morphological variability of B. cinerea isolates obtained from samples collected in commercial plantations of Japanese quince. Samples of plant parts with different fungal disease symptoms were collected in eight commercial plantations of Japanese quince during vegetation seasons of 2017 and 2018. Some samples were taken in Japanese quince plantations in Lithuania and Estonia. A total of 286 isolates of fungi were isolated from damaged shoots, leaves and fruits of Japanese quince plants, using potato dextrose agar. Botrytis cinerea isolates (39) were separated depending on the morphological characteristics and were proved by using methods of molecular biology. B. cinerea was isolated from shoots, leaves and fruits. The isolates of B. cinerea were described and classified into distinct morphological types depending on the characteristics of mycelia, sclerotia, reverse side of media and the presence or absence of sporulation

Possibilities for the biological control of yellow rust (Puccinia striiformis f. sp. tritici) in winter wheat in Latvia in 2017–2018

ArticleYellow rust, caused by Puccinia striiformis f. sp. tritici, is a significant wheat disease worldwide. In Latvia, the distribution of yellow rust has increased recently and new aggressive races have been identified. The aim of this research was to investigate the possibilities for the biological control of yellow rust in winter wheat. A field trial was established in a biological field of winter wheat in Latvia in 2017 and 2018. Biological products that contained Bacillus spp., Pseudomonas aurantiaca, Brevibacillus spp., Acinetobacter spp., and chitosan were used for treatments, and one variant was left untreated. The efficacy of products was evaluated by the AUDPC (area under the disease progress curve) comparison. Differences in the severity of yellow rust between the trial years were observed. In 2018, the severity of yellow rust was lower than in 2017. In untreated plots, on flag leaf, the severity varied from 10.9% to 32.5% in 2017 and from 1.4% to 6.5% in 2018. In 2017, the severity of yellow rust reached its maximum on 05.07. at wheat growth stage (GS) 79, and in 2018 – on 20.06. GS 79. Both in 2017 and 2018, no significant differences (p > 0.05) were found in AUDPC values among the variants. After two years of investigations, the results were not convincing; therefore, further research is needed

Variety, seeding rate and disease control affect faba bean yield components

ArticleFaba beans (Vicia faba L.) have been grown since 8000 years B.C. in the Middle East. Despite their long growing history in the world, there are only few researches carried out in Baltic region in last decades about variety, seeding rate and disease control effect on faba beans’ growth, development and yield formation. Research was carried out at the Latvia University of Life Sciences and Technologies during 2015–2017. Three factors were researched: A – variety (‘Laura’, ‘Boxer’, ‘Isabell’), B – seeding rate (30, 40 and 50 germinate able seeds m-2 ), C – treatment with fungicide (with and without application of fungicide Signum (1 kg ha-1 )). Meteorological conditions were diverse and sometimes caused stress for crop, but in general they favoured faba beans’ growth and development. High average yield of the field beans was obtained during all three trial years, however, yield differed significantly among them. Sowing time was constantly quite early, germination took longer time as expected due to the low air temperature, but later, temperature and humidity level improved and conditions were suitable for plant growth and development with some exceptions during flowering and pod filling. Number of productive stems per 1 m2 was significantly affected only by seeding rate. Plant height in trial site was affected by variety (p < 0.001), fungicide application (p = 0.008) and meteorological conditions (p < 0.001) of the year. Number of pods per plant differed depending on trial year (p < 0.001). Number of seeds per plant had a close positive correlation with number of pods per plant. Whereas number of seeds per pod was a relatively stable and typical characteristic for variety. We can observe correlation between faba bean yield and number of productive stems per 1 m2 at harvest, plant height, number of pods and seeds per plant

Field bean (Vicia faba L.) yield and quality depending on some agrotechnical aspects

ArticleDespite growing interest about field beans ( Vicia faba L.), only few researches have been carried out in Baltic countries on the possibility to increase field be ans’ yield and quality depending on different agrotechnical measures. Field trial was carried out in 2015, 2016 and 2017. Researched factors during all years were: A – variety (’Laura’, ’Boxer’, ’Isabell’), B – seeding rate (30, 40 and 50 germinate able se eds m - 2 ), C – treatment with fungicide (with and without application of fungicide). Beans’ yield (t ha - 1 ) and yield quality characteristics were detected in the trial. Temperature and moisture conditions were mostly suitable for high yield formation of fie ld beans in all three trial years. In all three trial years, field bean yield has been significantly affected by all factors. The highest yield ( p = 0.001) was provided by variety ‘Boxer’ in all years (6.10 – 7.74 t ha - 1 ). Thousand seed weight (TSW) was sign ificantly affected by variety and fungicide application. From agronomical point of view, crude protein level was not importantly affected by seeding rate changes or fungicide application. Volume weight was affected significantly by increased seeding rate o nly in 2016. Fungicide application also did not affect volume weight significantly during the whole trial period. Field bean yield increased by each year, but the main tendencies in all years were the same: higher yield and TSW was provided by variety ‘Box er’, but higher protein content and volume weight – by ‘Isabell’. Seeding rate increase gave positive impact on yield. Fungicide application affected field bean yield, but did not affect its quality significantly

Possibilities of cucumber powdery mildew detection by visible and near-infrared spectroscopy

Received: July 16th, 2021 ; Accepted: November 6th, 2021 ; Published: February 1st, 2022 ; Correspondence: [email protected] are one of the most demanded and widely grown greenhouse vegetables. Important factors that influence quality and quantity of yield are diseases. Powdery mildew (caused by Podosphaera xanthii and/or Golovinomyces cichoracearum), is one of the most harmful cucumber diseases. Early detection of mildew via non-destructive methods can optimize schemes of fungicide application. The study aimed to find regularities in the reflected light spectra, indices described in the literature, and severity of mildew. Plants were grown in the polycarbonate greenhouse under artificial lighting in a 16 h photoperiod with PAR at the tips of plants 200 ± 30 µmol m-2 s-1. Leaf reflection spectra were obtained using spectroradiometer RS-3500 (Ltd. Spectral Evolution). Spectral range 350–2,500 nm, bandwidth 1 nm. The severity of cucumber mildew was evaluated using 10 point scale (0- no symptoms, … 9 - the plant is dead). The vegetation indices found in the literature have been calculated. The obtained results show that the calculated indices have different sensitivities. The strongest correlation between the degree of cucumbers infection with powdery mildew and the light reflectance spectrum was found in the green range of visible light around 550 nm. Disease-Water Stress Index-2 (DSWI-2), Structure Intensive Pigment Index (SIPI), and Normalized Difference Vegetation Index (NDVI) are the most suitable indices for determining powdery mildew in cucumbers. New indices for detection of powdery mildew have been created. None of the studied indices allows determining the powdery mildew at the early stages of disease development when powdery mildew severity is below 10%

Brunatna plamistosc - najbardziej szkodliwa choroba pszenicy na Lotwie

Tan spot (Pyrenophora tritici-repentis) is one of the most important wheat diseases in Latvia. Significant spreading of this disease was observed from 1998. Field experiments were carried out at the Research and Training Farm „Peterlauki” of the Latvia University of Agriculture, during 1998-2003. Development of diseases was observed on 14 winter wheat varieties, dynamics of development was investigated on 'Donskaja polukarlikovaja' and 'Stava'. Assessments of the disease severity were carried out on the upper three leaves each week from the start of stem elongation to full ripening. Tan spot was observed at the stage of stem elongation in 2003, and only after flowering in 1999. Increase of the disease severity was slow until stage of milk ripeness, and only in late stages of wheat development sharp increase of the disease was observed. Total rate of infection (through the session of vegetation) was very slow (0,01-0,19), but during ripening rate achieved 0,5-0,6. The main reason of so unequal development of the disease seems changes in amount of infection sources. Other possible reason of rapid increase of the disease development is the relationship between leaf age and susceptibility to the disease. Further research is necessary for better understanding of tan spot life cycle.W latach 1998-2003 na terenie stacji doświadczalnej „Peterlauki” Łotewskiej Akademii Rolniczej podjęto badania, których celem była charakterystyka brunatnej plamistości liści w uprawach pszenicy ozimej. Oceniano stopień porażenia odmian oraz dynamikę rozwoju epifitozy. W każdym sezonie obserwacje prowadzono w odstępach tygodniowych, od fazy strzelania w źdźbło do pełnej dojrzałości roślin z wyjątkiem lat 1999 i 2003 w których ocena była wykonana odpowiednio: tylko po kwitnieniu zbóż i w fazie strzelania w źdźbło. Jak stwierdzono, wzrost stopnia porażenia roślin był powolny aż do fazy dojrzałości mlecznej. W okresie tym wskaźnik porażenia roślin osiągał wartość 0,01-0,19. Bardziej dynamiczny rozwój choroby obserwowano dopiero w późniejszych fazach rozwojowych roślin a wskaźnik porażenia roślin wynosił 0,5-0,6. Sugeruje się, że obserwowane różnice w dynamice przebiegu epifitozy brunatnej plamistości liści w trakcie sezonu wegetacyjnego są wynikiem zmieniającej się (wzrastającej) wraz z wiekiem roślin podatności na porażenie przez P. tritici-repentis oraz bardziej obfitym występowaniem inokulum patogena w miarę rozwoju epifitozy

Wlasciwosci cyklu rozwojowego chorob lisci pszenicy na Lotwie

The field observations were carried out in 1999-2004 on 29 fields in Latvia. Incidence and severities of wheat leaf diseases were determined. Tan pot caused by Drechslera tritici-repentis and Septoria leaf blotch, induced by Septoria tritici were the most harmful diseases at the time of research (incidence 10-100% and 1-100%, respectively). Also the incidence of powdery mildew, caused by Blomeria graminis was high (4-100%), while that of rusts (Puccinia tritici and P. striiformis) was very low. Changes in disease epidemics were determined and showed the differences between the analyzed diseases.Obserwacje polowe prowadzono w latach 1999-2004 na 29 plantacjach na Łotwie. Określano nasilenie występowania chorób liści pszenicy i stopień porażenia roślin na plantacjach. Brunatna plamistość liści powodowana przez Drechslera tritici-repentis i septorioza powodowana przez Septoria tritici okazały się najgroźniejszymi chorobami pszenicy w czasie prowadzenia badań (nasilenie występowania odpowiednio 10-100% i 1-100%). Nasilenie występowania mączniaka prawdziwego, powodowanego przez Blomeria graminis również było wysokie (4—100%), podczas gdy rdze (Puccinia tritici i P. striiformis) notowano tylko sporadycznie. Określano także zmiany zachodzące w czasie epifitoz i zanotowano różnice w cyklach rozwojowych pomiędzy badanymi chorobami