Publikasjoner

NIBIOs ansatte publiserer flere hundre vitenskapelige artikler og forskningsrapporter hvert år. Her finner du referanser og lenker til publikasjoner og andre forsknings- og formidlingsaktiviteter. Samlingen oppdateres løpende med både nytt og historisk materiale. For mer informasjon om NIBIOs publikasjoner, besøk NIBIOs bibliotek.

2022

Sammendrag

Harvest Weed Seed Control (HWSC) systems are used to collect and/or kill weed seeds retained on the weed plants at crop harvest. The effect of HWSC methods depends on the weeds seed retention at harvest. Therefore, delay in crop harvest reduces the efficiency of HWSC. In 2018, we studied the seed production and shedding pattern of Alopecurus myosuroides in a semi-field experiment in Taastrup, Denmark, to find the seed shedding time range of this species. In 2017 and 2018, we also followed the seed shedding pattern of A. myosuroides in a wheat field. Seeds of A. myosuroides were planted in pots in a greenhouse with a constant temperature of 5°C. In December 2017, the seedlings were transplanted in a box (120 × 80 cm2) located outdoor. In spring 2018, the number of plants was reduced to 14 providing a space of 685 cm2 for each plant. We surrounded each plant with a porous net to collect the seeds. The nets were checked once a week to record the beginning of the seed shedding period. Hereafter, seeds were collected weekly using a portable vacuum cleaner. Plants in the box started seed shedding in the second week of June and seed shedding continued for 12 weeks (end of August). In the wheat field, A. myosuroides plants surrounded by a net started to shed seeds in the third week of June and continued until wheat harvest on 31 July in 2017 and in the second week of July and continued until wheat harvest on 15 August in 2018. We found a significant difference between the weekly number of shed seeds in all three experiments (P

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Sammendrag

Clopyralid is a systemic herbicide used in oilseed rape and other crops. It was found in Danish honey from 2016 in concentrations exceeding the maximum residue level (MRL) of 0.05 mg kg−1. About 50% of the Danish honey is based on nectar from winter oilseed rape. In 2019 and 2020, winter oilseed rape fields were sprayed with clopyralid just before the assigned spraying deadline. At flowering, nectar and pollen samples were collected and the content of clopyralid was measured. Honey and pollen samples were also collected from beehives next to ten conventional winter oilseed rape fields sprayed with clopyralid. Clopyralid was found in nectar and pollen from the experimental fields, and in honey and pollen from beehives next to the conventional fields. For most samples the content in nectar and honey exceeded the MRL. The concentrations found, may not pose any health risk for consumers, as the MRL is based on the original detection limit and not on toxicological tests. However, it can have a significant economical consequence for the beekeepers, who are not allowed to sell the honey if the concentration of clopyralid exceeds 0.1 mg kg−1. Reducing the acceptable applicable rate of clopyralid or implementing an earlier deadline for spraying of clopyralid may reduce the risk of contaminating bee food products. However, if it is not possible to obtain a satisfactory effect of clopyralid on the weed flora under these conditions, spraying with pesticides containing clopyralid should be restricted in winter oilseed rape. Determination of an MRL value based on toxicological tests might result in a higher value and make it acceptable selling the honey containing higher levels of clopyralid.

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Sammendrag

Seed production is an important element of weed population dynamics, and weed persistence relies upon the soil seed bank. In 2017 and 2018, we studied the relationship between the aboveground dry biomass of common weed species and their seed production. Weeds were selected randomly in the fields, and we surrounded the plants with a porous net to collect shed seeds during the growth season. Just before crop harvest, weeds were harvested, the plants’ dry weights were measured, and the number of seeds retained on the weeds was counted. A linear relationship between the biomass and the number of seeds produced was estimated. This relationship was not affected by year for Avena spica-venti, Chenopodium album, Galium aparine, or Persicaria maculosa. Therefore, the data of the two seasons were pooled and analysed together. For Alopecurus myosuroides, Anagallis arvensis, Capsella bursa-pastoris, Geranium molle, Polygonum aviculare, Silene noctiflora, Sonchus arvensis, Veronica persica, and Viola arvensis, the relationship varied significantly between the years. In 2017, the growing season was cold and wet, and the slope of the regression lines was less steep than in the dry season in 2018 for most species. Capsella bursa-pastoris was the most prolific seed producer with the steepest slope.

Sammendrag

Harvest weed seed control takes advantage of seed retention at maturity by collecting weed seeds as they pass through the harvester. We assessed the seed production and shedding pattern of common weed species in two wheat and two oat fields in Denmark. The aim was to evaluate the possibility of harvesting retained seeds on weeds at crop harvest by a combine harvester based on estimation of weeds seed retention. Before flowering, ten plants of each weed species were selected and surrounded by a seed trap comprising of a porous net. When the plants started shedding seeds, the seeds were collected from the traps and counted weekly until crop harvest. Just before crop harvest, the retained seeds on the plants were counted and the ratio of harvestable seeds and shed seeds during the growing season were determined. The seed production and shedding patterns varied between the species. In oat, Anagallis arvensis L., Capsella bursa-pastoris (L.) Medik., Chenopodium album L., Fallopia convolvulus (L.) Á. Löve, Geranium molle L., Persicaria maculosa Gray, Polygonum aviculare L., Silene noctiflora L., Sinapis arvensis L., Sonchus arvensis L., Spergula arvensis L., Stellaria media (L.) Vill.,Veronica persica Poir., and Viola arvensis Murray retained on average 61, 52, 67, 44, 58, 32, 59, 95, 67, 23, 45, 56, 51, and 33%, respectively, of their produced seeds at crop harvest. In wheat, Alopecurus myosuroides Huds. and Apera spica-venti (L.) P. Beauv. retained on average 34 and 33%, respectively, of their seeds at harvest. Silene noctiflora was classified as a good target for harvest weed seed control; A. myosuroides, A. spica-venti, C. bursa-pastoris, C. album, F. convolvulus, G. molle, P.maculosa, Sinapis arvensis, Sonchus arvensis, Spergula arvensis and V. arvensis were classified as intermediate targets; and A. arvensis, P. aviculare, S. media and V. persica were classified as poor targets. The research shows that there is a great potential to reduce the input of weed seeds to the soil seed bank by harvest weed seed control. Keywords: Harvest weed seed control; Soil seed bank ; Weed seed retention

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Sammendrag

Fall armyworm (FAW) Spodoptera frugiperda (J.E. Smith, 1797) (Lepidoptera: Noctuidae) was recorded for the first time in 2016 attacking maize fields in central and west Africa. Soon after, several other regions and countries have reported the pest in almost the entire sub-Saharan Africa. In the present study, we assumed that (i) a variety of alternative plant species host FAW, especially during maize off-season, (ii) a wide range of local parasitoids have adapted to FAW and (iii) parasitoid species composition and abundance vary across seasons. During a two-year survey (from June 2018 to January 2020), parasitoids and alternative host plants were identified from maize and vegetable production sites, along streams and lowlands, on garbage dumps and old maize fields in southern and partly in the central part of Benin during both maize growing- and off-season. A total of eleven new host plant species were reported for the first time, including Cymbopogon citratus (de Candolle) Stapf (cultivated lemon grass), Bulbostylis coleotricha (A. Richard) Clarke and Pennisetum macrourum von Trinius (wild). The survey revealed seven parasitoid species belonging to four families, namely Platygastridae, Braconidae, Ichneumonidae, and Tachinidae associated with FAW on maize and alternative host plants. The most abundant parasitoid species across seasons was the egg parasitoid Telenomus remus (Nixon) (Hymenoptera: Platygastridae). These findings demonstrate FAW capability to be active during the maize off-season in the selected agro-ecologies and provide baseline information for classical and augmentative biocontrol efforts.