Optimizing Insecticide Application Timing for Broad Bean Weevil Control and Minimizing Crop Damage in Broad Bean (Vicia faba Linn.)

During the growing seasons of 2018 to 2020, a field experiment in broad bean (Vicia faba L.) was conducted at the Lithuanian Research Centre for Agriculture and Forestry. The objective of the study was to explore the effects of the timing of insecticide application on the abundance, damage, and control of the broad bean weevil (Bruchus rufimanus Boh.). The experiment included four spray regimes and an untreated control. Yellow water traps were utilized to monitor the broad bean weevil from germination to senescence. Results indicate that broad bean weevil infestation occurred in all study years, with the highest density of adults observed during the flowering stage. Damage to seeds ranged from 23% to 59.62%. The data suggest that B. rufimanus infestation can result in a 19.1% reduction in seed yield. However, spraying when the daily temperature exceeded the threshold for adult activity for 3 days and at the end of flowering produced a significant increase in yield of 13.3% and 6.6%, respectively. Additionally, the spray at the end of flowering reduced damaged seeds by 21.4-48%.

Bruchus rufimanus Boh. Effect on Broad Bean Seed Quality and the Infection Level of Seed-Borne Fungal Pathogens

Broad bean weevil (Bruchus rufimanus Boh.) is considered an economically important insect pest of the broad bean crop. Its damage starts when larvae burrow into the seed and feed on endosperm or kill the embryo, thus the seed cannot germinate. The microbiological quality and consumer safety of broad bean may be compromised by holes. This study was performed during 2018-2020 to estimate the effect of seed damage by B. rufimanus on seed quality, germination rate and seedling growth, and on the incidence of seed-borne fungal pathogens. Broad bean seeds were collected and classified as damaged by B. rufimanus or non-damaged. There was a relationship between broad bean weevil damage and an increase in fungal contamination. Results showed that germination decreased from 97.2% for non-damaged seeds to 81.4% for the seeds with B. rufimanus damage. Seven fungal genera were identified: Fusarium spp., Alternaria spp., Aspergillus spp., Penicillium spp., Cladosporium spp., Mucor spp. and Botrytis spp. The most common fungal genus was Cladosporium spp. Our research shows that B. rufimanus negatively affects the germination of its host's seeds and decreases the development of seedlings.

Oilseed Rape, Wheat, and Barley Grain Contamination as Affected by Different Glyphosate Usage

Glyphosate is one of the most widely used herbicides, but is still in the spotlight due to its controversial impact on the environment and human health. The main purpose of this study was to explore the effects of different glyphosate usages on harvested grain/seed contamination. Two field experiments of different glyphosate usage were carried out in Central Lithuania during 2015-2021. The first experiment was a pre-harvest application, with two timings, the first according to the label (14-10 days), and the other applied 4-2 days before harvest (off-label), performed in winter wheat and spring barley in 2015 and 2016. The second experiment consisted of glyphosate applications at label rate (1.44 kg ha^-1) and double dose rate (2.88 kg ha^-1) at two application timings (pre-emergence of crop and at pre-harvest), conducted in spring wheat and spring oilseed rape in 2019-2021. The results suggest that pre-emergence application at both dose rates did not affect the harvested spring wheat grain or spring oilseed rape seeds-no residues were found. The use of glyphosate at pre-harvest, despite the dosage and application timing, led to glyphosate's, as well as its metabolite, aminomethosphonic acid's, occurrence in grain/seeds, but the amounts did not reach the maximum residue levels according to Regulation (EC) No. 293/2013. The grain storage test showed that glyphosate residues remain in grain/seeds at steady concentrations for longer than one year. A one year study of glyphosate distribution within main and secondary products showed that glyphosate residues were mainly concentrated in wheat bran and oilseed rape meal, while no residues found in cold-pressed oil and wheat white flour, when glyphosate used at pre-harvest at the label rate.

Effects of Pea (Pisum sativum L.) Cultivars for Mixed Cropping with Oats (Avena sativa L.) on Yield and Competition Indices in an Organic Production System

The benefits of cereal-legume mixed cropping is a sustainable agricultural practice. However, knowledge of the genotypic differences of semi-leafless pea varieties is not enough to help them compete with cereals. In this study, the effects of Lithuania's newest Pisum sativum cultivars ('Egle DS' and 'Lina DS') and, for comparison, a control cultivar ('Jūra DS') established with Avena sativa in mixed cropping system were investigated. Three years of field trials (2018, 2019 and 2020) with four experiments involved three different mixtures of each field pea cultivar with oat. The aboveground biomass of mixed cropped new field pea cultivars was found to be significantly higher: biomass of cultivars 'Egle DS' increased by 17.0% and 'Lina DS' by 7.2% on average compared with the control cultivar 'Jūra DS'. For the mixed cropping system, statistically greater total aboveground biomass was observed with plant ratios of 50% pea + 50% oat and 60% pea + 40% oat compared to peas monocultures. Mixed cropped oat was the dominant species in all tested mixture compositions; however, the highest total grain yield of mixed crops was obtained when new pea 'Lina DS' and 'Egle DS' cultivars were included in the mixtures compared with the control cultivar. The new pea cultivar 'Egle DS' had a greater effect on protein content compared to other tested pea cultivars. In the new pea cultivars 'Lina DS' and 'Egle DS', the higher photosynthetic capacity and aboveground biomass of mixed cropped pea with oat showed mixture effects in the mixed cropped system and could increase total yield compared with pea monoculture. Generally, the new pea cultivars displayed a greater Land Equivalent Ratio (LER) value, resulting in the greatest yield among the mixtures on average for all three years and all four experiments. Future research could optimize the effects of pea cultivar mixtures with cereals to further improve the yield of organic mixed cropping systems.

The influence of harvesting time and meteorological conditions on the occurrence of Fusarium species and mycotoxin contamination of spring cereals

BACKGROUND

The aim was to determine the influence of harvesting time and meteorological conditions on the occurrence of Fusarium spp. and mycotoxins in the grain of spring cereals. A field experiment was performed in 2016-2018 with spring oat (Avena sativa L.) and spring triticale (× Triticosecale Wittm.) plots. Grain samples of oat and triticale were analysed for Fusarium infection and co-contamination with mycotoxins deoxynivalenol (DON), zearalenone (ZEA) and T-2 toxin (T-2).

RESULTS

Results from the three-year study showed that the occurrence of Fusarium spp. fungi and mycotoxins produced by them in spring oat and triticale grain was most influenced by the meteorological conditions at harvesting time and crop species.

CONCLUSIONS

It was found that in all experimental years, F. poae, F. tricinctum and F. sporotrichioides predominated in oat grains and F. graminearum, F. sporotrichioides and F. avenaceum predominated in spring triticale; as a result, oat grains were more contaminated with T-2 and triticale grains with DON and ZEA. Due to the rainy harvesting period in 2017, the contamination level of Fusarium fungi of grain of both crop species was 100%, and the concentrations of DON and ZEA in the samples of spring triticale were several times higher than those set forth in the EU regulation. Co-occurrence of all three mycotoxins analysed (DON, ZEA and T-2) was identified in these samples. © 2020 Society of Chemical Industry.