Jämförelse mellan olika system för ogräsrensning i lökodling

Ogräs är ett stort problem i lökodling och kan orsaka stora skördeförluster för lantbrukaren. För att jämföra effekterna av olika metoder för ogräsrensning i lök på ogräspopulationernas marktäckning (ogräseffekt) samt lökodlingens avkastning och de skördade lökarnas storlek såddes därför ett randomiserat blockförsök med lök på Almhaga gård i Skåne, Sverige, den 13 april 2022. I fältförsöket studerades sex rensningsmetoder som repeterades i fyra block. Handrensning utfördes regelbundet under hela odlingsperioden och kemisk bekämpning gjordes vid sju tillfällen. Rensning med robotar från Ekobot utfördes på fyra olika sätt: Robotrensning var tredje respektive var sjätte dag med avslutande handrensning samt robotrensning var tredje respektive var sjätte dag utan avslutande handrensning. Täckningsgrad av ogräs skattades tre gånger under maj-juni, blastlängd mättes för tio slumpmässigt utvalda lökar per behandling vid ett tillfälle i juni, skörd (färskvikt kg/ha) samt storleksklassificering (0-40, 40-60 och 60-80 mm) av producerad lök genomfördes i början av september. Resultatet visade signifikant skillnad för blastlängd mellan leden robotrensning var tredje dag- (32,7 cm) och sjätte dag (32,4 cm) utan handrensning med handrensade ledet (27,7 cm) i block 4. Inga signifikanta skillnader i skörd eller storleksfördelningen fanns mellan behandlingarna. Medelskörden låg på ca 62 600 kg färskvikt/ha och storleksfördelning var 4% (0-40mm), 60% (40-60 mm) respektive 36% (60-80mm). För ogräseffekten observerades vissa signifikanta skillnader för ogräsen svinmålla (Chenopodium album), åkerbinda (Fallopia convolvulus) och korsört (Senecio vulgaris) men inte för baldersbrå (Tripleurospermum inodorum) och våtarv (Stellaria media). Sämre effekt erhölls mot svinmålla, åkerbinda och korsört i ledet med robotrensning var sjätte dag utan handrensning jämfört med de andra leden. Ogräs som roboten inte fick en fullträff på och blev rensade i tidigt stadium hade en tendens att växa sämre men ändå överleva och utveckla en förstärkt rothals. Detta kan möjligen förklara skillnaden mellan ogräsens olika respons på behandling, som kan förebyggas genom högre frekvens av robotrensning. Studien visade att robotrensning gav samma effekt som handrensning och kemisk bekämpning gällande skörd och storleksfördelning. En enklare ekonomisk beräkning visade, vid en jämförelse mellan rådande prissättning för roboten och lön för handrensare, att en ekonomisk vinst på ekologiska gårdar fås vid ett ogrästryck som kräver mer än 120 timmar handrensning per hektar och år. Vanligtvis behövs runt 100–200 timmar handrensning per hektar för godkänt resultat men i särskilda fall kan det vara så högt som ≥500 timmar om ogrästrycket är stort. För konventionella gårdar krävs istället en skördeökning runt 10 % ifall robotrensning används istället för herbicider för att få en ekonomisk vinst. Lärdomarna från detta försök kommer att användas för att förbättra rensningstekniken hos robotarna. Framöver förväntas därmed en signifikant positiv effekt på skörd och ogräsbekämpning och i framtiden kommer ogräsrensning med autonoma maskiner bli en allt vanligare syn inom lantbruket.Weeds may cause large yield reductions in onion cultivation. Therefore, a randomized block experiment with onions was performed in Skåne, Sweden in 2022 to compare the effects of different weed control methods in onions on weed population, ground cover (weed effect) as well as onion crop yield and harvested onion size. In the field experiment, six weeding methods were studied and repeated in four blocks. Manual weeding was performed regularly throughout the cultivation period, and chemical herbicides were applied seven times. Weeding with robots from Ekobot was done in four different ways: robot weeding every third and sixth day with final manual weeding, and robot weeding every third and sixth day without final manual weeding. Weed coverage was assessed three times during May and June, and the length of onion shoots was measured once in June. Harvest (fresh weight kg/ha) and size classification (0-40, 40-60 and 60-80 mm) of the produced onions were carried out in early September. A significant difference occurred in shoot length between the treatments of robot weeding every third day (32,7 cm) and every sixth day (32,4 cm) without manual weeding compared to the manually weeded plot (27,7 cm) in block 4. There were no significant differences in yield or size distribution between the treatments. The average yield was approximately 62 600 kg fresh weight/ha and the size distribution was 4% (0-40 mm), 60% (40-60 mm) and 36% (60-80 mm). For weed effect, some significant differences were observed for the weeds white goosefoot (Chenopodium album), black bindweed (Fallopia convolvulus) and common groundsel (Senecio vulgaris), but not for scentless false mayweed (Tripleurospermum inodorum) and chickweed (Stellaria media). The treatment with robot weeding every sixth day without manual weeding showed poorer effects against white goosefoot, black bindweed and common groundsel compared with the other treatments. Weeds that the robot missed and not weeded at an early stage tended to grow weaker but still survived and developed a strengthened root neck. This could possibly explain the variation in weed response to treatments, which can be prevented through a higher frequency of robot weeding. The study demonstrated that robot weeding provided similar effects to manual weeding and chemical control regarding crop yield and size distribution. An economic analysis showed that on organic farms, using robots becomes economically advantageous when weed pressure requires more than 120 hours of manual weeding per hectare and year. Typically, around 100-200 hours of manual weeding per hectare are needed for acceptable results, but in special cases, it can be as high as ≥500 hours if the weed pressure is significant. For conventional farms, a yield increase of around 10% is required to achieve an economic benefit when using robot weeding instead of herbicides. The conclusion from these experiments will be used to improve the weeding technique of the robots. In the future, this is expected to have a significantly positive impact on weed control and crop yield. Weed control with autonomous machines is therefore anticipated to become a more common sight in agriculture

A controlled study on gastrointestinal nematodes from two Swedish cattle farms showing field evidence of ivermectin resistance

Anthelmintic resistance (AR) is an increasing problem for the ruminant livestock sector worldwide. However, the extent of the problem is still relatively unknown, especially for parasitic nematodes of cattle. The effect of ivermectin (IVM) (Ivomec inj.®, Merial) was investigated in Swedish isolates of gastrointestinal nematode (GIN) populations showing signs of AR in the field to further characterise the AR status by a range of in vivo and in vitro methods. Three groups, each of 11 calves, were infected with an equal mixture of third stage larvae (L3) of Cooperia oncophora and Ostertagia ostertagi. Group A was inoculated with an IVM-susceptible laboratory isolate and groups B and C with isolates originating from 'resistant' cattle farms. Faecal egg counts (FEC) were monitored from 0 to 45 days post infection (d.p.i.), and L3 were harvested continuously for larval migration inhibition testing (LMIT) and species-specific PCR (ITS2). At 31 d.p.i., one calf from each group was necropsied and adult worms were recovered pre-treatment. At 35 d.p.i., calves from all groups were injected with IVM at the recommended dose (0.2 mg/kg bodyweight). At 45 d.p.i., another two animals from each group were sacrificed and established gastrointestinal worms were collected and counted. A few animals in all three groups were still excreting eggs (50-150 per g faeces) 10 days post IVM injection. However, there was no significant difference in the FEC reductions in groups A (95%; 95% CI 81-99), B (98%; 92-100) and C (99%; 97-100) between 35 and 44 d.p.i. Furthermore, LMIT showed no significant difference between the three groups. Approximately 100 adult O. ostertagi were found in the abomasum of one calf (group B), whereas low to moderate numbers (400-12 200) of C. oncophora remained in the small intestine of the calves in all three groups at 45 d.p.i. PCR on L3 harvested from faecal samples up to 10 days post treatment showed a ratio of 100% C. oncophora in the calves inoculated with isolates A and B, whereas C also had 8% O. ostertagi. Overall, this experiment showed that the animals were successfully treated according to the Faecal egg count reduction test (FECRT) standard (≥ 95% reduction). However, several adult worms of the dose-limiting species C. oncophora demonstrably survived the IVM treatment

Transmission patterns of Fasciola hepatica to ruminants in Sweden

Transmission patterns of Fasciola hepatica were investigated on beef cattle (n = 3) and sheep (n = 3) farms in Sweden between 2011 and 2012. The dynamics of fluke infection, particularly estimated time of infection, were screened each grazing season by ELISA detection of antibodies in lambs (n = 94) and first grazing season calves (n = 61). Colostral transfer of F. hepatica antibodies from seropositive ewes was detected in sheep up to 11 weeks of age. In sheep, the estimated time of infection differed significantly between herds and years. Typical 'winter infection' was observed on two sheep farms in 2012, but the most prevalent transmission pattern was found to be 'summer infection', characterised by infection of animals in late summer by F. hepatica originating from overwintered and/or spring-excreted eggs. In contrast, beef calves were infected mainly in September-October ('summer infection'). Furthermore, lymnaeid and succineid snails were collected on the pastures used by these animals both in spring and in the autumn each year. In total, 1726, 588, 138, 130, 93 and 42 specimens of Galba truncatula, Lymnaea palustris, Lymnaea glabra, Lymnaea fuscus, Radix peregra and Succinea putris, respectively, were collected and identified. These were subsequently examined for the presence of F. hepatica DNA by species-specific PCR and the findings compared against mean monthly rainfall and temperature data for each farm. The main intermediate host of the liver fluke was G. truncatula, with a prevalence range of F. hepatica infection from 0% to 82%. Only 1 out of 42 terrestrial S. putris tested positive for F. hepatica, casting doubt on the role of this species in transmission of F. hepatica in Sweden. In conclusion, two main peak periods of infection were observed: May-June (from overwintered infected snails = 'winter infection') and August-September (from metacercariae developed and produced by snails during summer = 'summer infection'). The occurrence and frequency of 'winter infection' were dependent on local environmental factors such as snail habitat availability or grazing behaviour of animals, rather than on climatic factors

Trends in Occupational Exposure to Styrene in the European Glass Fibre-Reinforced Plastics Industry

Aim: This study presents temporal trends of styrene exposure for workers in the European glass fibre-reinforced plastics (GRP) industry during the period 1966–2002

Transmission patterns of Fasciola hepatica to ruminants in Sweden

Transmission patterns of Fasciola hepatica were investigated on beef cattle (n = 3) and sheep (n = 3) farms in Sweden between 2011 and 2012. The dynamics of fluke infection, particularly estimated time of infection, were screened each grazing season by ELISA detection of antibodies in lambs (n = 94) and first grazing season calves (n = 61). Colostral transfer of F. hepatica antibodies from seropositive ewes was detected in sheep up to 11 weeks of age. In sheep, the estimated time of infection differed significantly between herds and years. Typical 'winter infection' was observed on two sheep farms in 2012, but the most prevalent transmission pattern was found to be 'summer infection', characterised by infection of animals in late summer by F. hepatica originating from overwintered and/or spring-excreted eggs. In contrast, beef calves were infected mainly in September-October ('summer infection'). Furthermore, lymnaeid and succineid snails were collected on the pastures used by these animals both in spring and in the autumn each year. In total, 1726, 588, 138, 130, 93 and 42 specimens of Galba truncatula, Lymnaea palustris, Lymnaea glabra, Lymnaea fuscus, Radix peregra and Succinea putris, respectively, were collected and identified. These were subsequently examined for the presence of F. hepatica DNA by species-specific PCR and the findings compared against mean monthly rainfall and temperature data for each farm. The main intermediate host of the liver fluke was G. truncatula, with a prevalence range of F. hepatica infection from 0% to 82%. Only 1 out of 42 terrestrial S. putris tested positive for F. hepatica, casting doubt on the role of this species in transmission of F. hepatica in Sweden. In conclusion, two main peak periods of infection were observed: May-June (from overwintered infected snails = 'winter infection') and August-September (from metacercariae developed and produced by snails during summer = 'summer infection'). The occurrence and frequency of 'winter infection' were dependent on local environmental factors such as snail habitat availability or grazing behaviour of animals, rather than on climatic factors

A Scramble for Rents : Foreign Aid and Armed Conflict

Previous research has not specified the circumstances under which foreign aid may increase the probability of armed conflict. The purpose of this dissertation is to address this gap by employing a theoretical framework in which foreign aid produces incentives for a rent-seeking scramble among elites. A set of conditions affecting the likelihood of armed conflict are identified and tested on global data in a series of statistical analyses. Paper I argues and finds that foreign aid increases the probability of armed conflict in states where there are few constraints on executive power, allowing for a scramble for rents. Paper II proposes and finds a threshold effect of aid, such that the likelihood of armed conflict increases only when aid has reached a certain level. Paper III suggests and demonstrates that sudden negative changes in aid flows enhance the risk of armed conflict as well as coup attempts, as aid shortfalls accelerate distributional conflict over aid rents. Paper IV claims and shows that civil wars are less likely to be terminated by settlement in the form of elections when conflict parties are dependent on rents. In sum, this dissertation contributes by theoretically specifying and empirically identifying conditions under which foreign aid increases the probability of armed conflict