Controlling Echinochloa crus-galli in cereals, potatoes and vegetables

Echinochloa crus-galli (ECHCG) is a noxious weed in Norway and has expanded its distribution in recent years from areas near the coast of Oslo fjord into the whole region and has established from Agder County in south to Trøndelag County in north. It can give high yield losses and be difficult to control. The main objective of this project was to find effective direct and preventive control measures against ECHCG in cereals, potatoes and vegetables based on new knowledge on the biology of this species in Norway. The project was conducted together with the extension service (NLR) around the Oslo fjord and Norwegian University of Life Sciences, and consisted of 4 work packages (WPs). In WP1 emergence and phenological development of ECHCG were assessed in 1 pot trial and in field trials in with or without competition from cereals (4 fields), and in fields with plastic or fleece cover (3 potato trials, 1 trial without crop). Preliminary results from cereals showed that biomass and number of seeds of ECHCG were more reduced than total emergence and phenological development with a cereal crop present compared to crop-free conditions. The time of emergence was not influenced by presence of a crop. Emergence started later in potato grown under plastic than under fleece cover expressed as days after disturbance, while less so if expressed as day degrees. Phenological development in potatoes were disrupted by roe hoeing and reached heading in only 1 field. First versions of mathematical models are developed based on day degrees. In WP2 we investigated direct control measures against ECHCG. In spring cereals herbicides and application technique (crop tilter) at different times were studied (6 field trials). Preliminary results showed that Attribut Twin (early, and if soil is moist) and Axial (late with or without crop tilter) provided good control. Three trials indicated that weed harrowing in cereals could reduce ECHCG, but the results were uncertain due to few plants. In an outdoor pot trial with hand weeding, cutting or glyphosate at and 7-10 days after ear emergence of ECHCG, the number of viable seeds was mostly reduced by hand weeding and glyphosate. We investigated the effect of herbicides in 5 potato fields grown under plastic or fleece cover or in the open. Herbicides could control ECHCG, but not always. In parsnip we did field trials (3 trials, 2017-18) with strategies based on row hoeing and herbicides (3 applications). In year 1, ECHCG appeared fully controlled, but at the last assessment a considerable amount was present which most likely constituted late emergence. In year 2, the strategy with Agil late in season controlled ECHCG successfully, whereas the earlier measures (row hoeing+Fenix+Centium±Boxer) gave max. 41% control. In a pot trial testing thermal weed control (hot water) before ECHCG emergence, the highest dose gave about 60% control. We expect higher doses to improve efficacy. In another trial with thermal control (soil exposed to water steam), no seeds from five populations germinated when mean soil temperature was at least 94°C. At second highest temp. (83°C) up to 20% germinated. In WP3 we measured biological control of ECHCG in cereals, i.e. the rate of predation of seeds laying at the ground. In spring cereals (4 trials), seed cards were out in 4 periods; crop closure (T1), pre-harvest (T2), stubble (T3), stubble late autumn (T4). Half of the cards were inside cages preventing larger predators like rodents and birds to reach the seeds, while insects pass freely. The predation rate was higher from cards without vs. inside cages: without cage on average 20% (T1, T3), 30% (T4) and 50% (T2) compared to about 2% (T1, T2), 5% (T4) and 13% (T3) in cage. This means that animals larger than insects play a more important role than insects in conservation biological control of ECHCG seeds. With pitfall traps we found that three carabid beetle species known to eat seeds were common in the fields. In AP3, we also tested if a systematic visual inspection (corresponding to Avena fatua-inspection) is a proper way to reveal and map ECHCG in its establishment phase in cereals. ECGCG is known to be plastic and have individuals at same growth stage which are either tall or low compared with the crop. In a spring barley field, ECHCG lower than the crop was found both early July (only low plants, max. 15 cm/3 tillers), end of July and pre-harvest (two latter times: both low and tall plants, max. 70 cm/full flowering). Totally for the 3 inspection days, only 24% of the ECHCG sites had plants taller than crop. This shows that systematic field inspection can reveal low ECHCG plants, and that it is important not to limit the inspection to plants taller than crop to detect and map ECHCG in the field. As a part of WP4 we have disseminated about the project and ECHCG in many meetings, field days for farmers, advisors, scientists and other stakeholders and via the internet, brochures and a video.

Virkninger: PROSJEKTDELTAKERE har fått mer kunnskap om ugrasarten hønsehirse - både biologi, oppspiring, hvordan den oppfører seg, hvor alvorlig og tilpasningsdyktig den er, hvordan oppdage den og bekjempe den med ulike forebyggende og direkte kjemiske og alternative tiltak i korn, potet og grønnsaker. DYRKERE, RÅDGIVERE, FORVALTNING og andre NÆRINGSAKTØRER har fått tilgang til denne kunnskapen gjennom omfattende formidling fra prosjektet. Prosjektet har gitt grunnlag for en Masteroppgave og bidratt til høyere UTDANNING. FORSKERE har fått mer kunnskap og bakgrunn for videre forskning på biologi, modellering og integrert bekjemping av hønsehirse og bidratt til mer internasjonalt samarbeid. Effekter: Mer bevissthet på og kunnskap om denne skadelige arten, kan bidra til tidlig oppdagelse av den i norske åkre og forhindre spredning ved å sette inn tiltak tidlig. Brukere får flere verktøy innen integrert plantevern, opprettholder avlingsnivået og bærekraftig matproduksjon i framtida.

Echinochloa crus-galli is an increasing noxious weed in Norway. The species has expanded its distribution in recent years from areas near the coast of Oslo fjord into the whole region, and has established from Aust-Agder County in south to Hedmark County in north. Well-adapted biotypes in Østfold and Vestfold counties today competes well in spring cereals in Norway. Yield losses of 20% were recorded in a field trial in spring wheat in Vestfold County. Yield losses in less competitive vegetable crops, due to uncontrolled E. crus-galli infestations, will be much higher than in cereals. Local extension service and farmers claim that they have trouble in controlling the weed even with effective herbicides at hand. In contrast to Norway, E. crus-galli is not considered a problem in spring cereals in other Nordic countries. The main objective is to find effective direct and preventive control measures against Echinocloa crus-galli in cereals, potatoes and vegetables based on new knowledge on the biology of this species in Norway. Emergence pattern and phenological development, seed production and seed viability are biological variables important to take into account to integrate control measures and give good decision support to the farmers. If a small E. crus-galli infestation is not successfully controlled and has little competition from a crop, it can produce many seeds that can give a large infestation in succeeding years. This study in collaboration with an European working group aims to test and calibrate the Italian emergence model of E. crus-galli and to investigate if it is suitable under various conditions, including Norway. When optimal control stages are reached will probably the efficacy of different herbicides and other control measures, be improved. We will investigate mechanical, chemical and thermal control measures suitable early and late in the season and possibility for early detection of E. crus-galli and biological control by seed predation.