A herbicide resistance risk assessment for weeds in maize in New Zealand

Despite an extensive history of research into herbicide resistance in New Zealand maize, some aspects remain understudied. Herbicide resistance was first detected in New Zealand in the 1980s in maize crops, with atrazine resistance in Chenopodium album L. and Persicaria maculosa Gray. Since then, Chenopodium album has also developed resistance to dicamba, and in the last five years Digitaria sanguinalis (L.) Scop. populations have been reported to be resistant to nicosulfuron. Here we estimate the risk of herbicide resistance arising in 39 common maize weeds. A list of weeds associated with maize was generated, omitting uncommon weeds and those that grow outside of the maize growing season. Weeds were ranked for their risk of evolving herbicide resistance with a scoring protocol that accounts for the specific herbicides used in New Zealand maize. Seven weed species were classified as having a high risk of developing herbicide resistance: Echinochloa crus-galli (L.) P.Beauv., Chenopodium album, Eleusine indica (L.) Gaertn., Xanthium strumarium L., Amaranthus powellii S.Watson, Solanum nigrum L. and Digitaria sanguinalis. Seventeen species were classed as moderate risk, and 15 were low risk. Herbicide classes associated with more resistant species were classed as high risk,these included acetohydroxy acid synthase inhibitors and photosystem-II inhibitors. Synthetic auxins had a moderate risk but only two herbicides in this class (dicamba and clopyralid) are registered for maize in New Zealand. Other herbicide mode-of-action groups used in maize were low risk. We recommend outreach to farmers regarding weed-control strategies that prevent high-risk species from developing resistance. High-risk herbicide groups should be monitored for losses of efficacy. Resistance surveys should focus on these species and herbicides.

Hot foam and hot water for weed control: A comparison

Thermal weed control plays an important role in managing weeds in synthetic herbicide-free systems, particularly in organic agriculture and in urban areas where synthetic herbicides are prohibited. This study compares the impact on weed control of increased doses of hot water and hot foam (i.e. 0, 0.67, 1.67, 3.33, 5.00, 6.67 and 8.33 kg m–2). The doses were applied using the same machine. The temperatures, weed control effectiveness, weed regrowth after the death of the aboveground vegetative weed tissues, and weed dry biomass 30 days after the treatments were studied in two experimental fields with a different weed composition (i.e. Site I and Site II). The results showed that difficult weeds to control, such as Cynodon dactylon (L.) Pers., Digitaria sanguinalis (L.) Scop. and Taraxacum officinale Weber, like all the other species in the initial weed populations in the two experiments, died after lower doses of hot foam compared to hot water. Adding foam to hot water made it possible to lower the required dose of water by at least 2.5-fold compared to hot water used alone. By insulating the weeds, the foam led to higher peak temperatures and slower temperature decay, thus determining an effective weed control with lower doses compared to hot water. Starting from 11 days and 16 days after treatments (for Site I and Site II, respectively), there were no statistically significant differences in weed regrowth between hot foam and hot water at all the doses applied. There were no differences between the dry biomass of weeds collected 30 days after treatments when the same doses of hot foam and hot water were used.

Herbicide in Weed Management of Wheat (Triticum aestivum L.) and Rainy Season Rice (Oryza sativa L.) under Conservation Agricultural System

Conservation agriculture (CA) based practices are gaining popularity in smallholder farming systems recently because they ensure soil quality and soil health, and they also reduce the total cultivation costs. However, weeds are a major hinderance to achieving the desired yield of crops in cereal-based cropping systems under CA-based practices. Proper weed management is a big challenge for crop growers to reduce the labor demand and cost of production. Considering these burning issues, a field study was done with a CA-based rice–wheat–mung bean (Vigna radiata L.) cropping pattern in two consecutive years (2017–2018 and 2018–2019). The study aimed to understand the types and distribution of weeds in non-puddled rice fields and also in strip-planted wheat fields in sandy loam textured soil with low organic matter (0.87%) content. Furthermore, we also tried to discover the most economic and effective ways to manage weeds in both cereals of the cropping pattern. The performance of two herbicides—pendimethalin (as pre-emergence) and carfentrazone–ethyl + isoproturon (as post-emergence)—for strip-planted wheat and three herbicides—two pre-emergence herbicides pretilachlor and pyrazosulfuron–ethyl as well as one post-emergence herbicide, bispyribac–sodium—for non-puddled rainy season rice were evaluated, where the ‘weedy check’ and ‘weed free’ treatments were considered as a control. In a two-year field experiment, eight weed species in the strip-planted wheat field during the first year and fourteen species in the second year were identified. Among them, three grasses such as Cynodon dactylon (L.) Pers., Digitaria sanguinalis (L.) Scop. and Echinochloa colona (L.) Link and one broadleaf weed Physalis heterophylla (L.) Nees, were found to the dominant in both years. During the first season, the dominant weed species in strip-planted wheat was Physalis heterophylla (L.); Digitaria sanguinalis (L.) Scop was dominant in the second year. In a non-puddled field of rainy season rice, eleven weed species were found in the first year and twelve species were found in the second year. Among the weed species, four types of grasses (Cynodon dactylon (L.) Pers., Leptochloa chinensis (L.) Nees, Echinochloa colona (L.) Link and Leersia hexandra (Sw.), one sedge (Fimbristylis miliacea (L.) Vahl) and four broadleaf weed species (Ludwigia decurrens (Walter), Jussiaea repens (L.), Enhydra fluctuans (Lour) and Alternanthera sessilis (L.) R.Br. ex DC.) were found the common in both years. The most dominant weed in non-puddled rainy season rice was Leptochloa chinensis (L.) for the first year and Alternanthera sessilis (L.) for the second year. The study revealed that the sequential application of pendimethalin as pre-emergence treatment followed by carfentrazone–ethyl + isoproturon as post-emergence treatment were most effective and economically viable for weed control in strip-till wheat because they achieved the highest grain and straw yields. For weed management in non-puddled rainy season rice, the herbicide pyrazosulfuron–ethyl applied as pre-emergence treatment and bispyribac–sodium as the post-emergence application were found to be the most effective combination to obtain a desirable yield.

Effects and correlation analysis of different host-plant components on physiological indexes in Spodoptera frugiperda

Spodoptera frugiperda (Lepidoptera: Noctuidae) is an invasive pest that ravaging crops in many provinces of China. In order to specifically control this invasive pest, understanding of the relationship between the insect and the host is necessary. In this study, we have compared the biological and nutritional indexes of S. frugiperda by feeding it with five different host-plants (Zea mays, Triticum aestivum, Digitaria sanguinalis, Glycine max and Eleusine indica). The biological and nutritional indexes of Z. mays feeding S. frugiperda were the best. However, the pupa weight and fecundity of S. frugiperda fed with G. max and E. indica were significantly lower than those fed with other hosts, efficiency of conversion of digested food (ECD) and efficiency of conversion of ingested food (ECI) were also lower than others. The total phenol content was negatively correlated with the biological and nutritional indexes of S. frugiperda, while the C/N content was positively correlated. When fed on different host plants, the biological and nutritional indexes of S. frugiperda were different, but all of them could complete the life cycle. Therefore, in the absence of Z. mays, the S. frugiperda may also harm other host plants, and host plants with high C/N content can also with the risk of being infected.

Evaluación de herbicidas en pre y pos emergencia en el cultivo de alcaucil (Cynara cardunculus var. scolymus, L)

Uno de los principales problemas productivos del alcaucil son las malezas, siendo necesario disponer de herbicidas que efectúen un adecuado control. Se evaluó la eficacia de herbicidas en el control de malezas en etapas iniciales del cultivo, y la fitotoxicidad sobre el mismo. El experimento se realizó en la FCA, UNR, en Madrigal, sembrado en octubre y trasplantado en noviembre de 2014. Se aplicaron en preemergencia de malezas: S-metolacloro, Oxifluorfen, Pendimetalin, Linuron, Prometrina y además, los dos últimos en posemergencia. Fue analizado el porcentaje de eficacia de control de los herbicidas sobre Portulaca oleracea, Lamium amplexicaule, Eleusine indica, Digitaria sanguinalis, Echinocloa sp., Chenopodium album y Amaranthus quitensis. La fitotoxicidad se midió con escala arbitraria (1:no afectadas; 2:levemente afectadas; 3:afectadas; 4:muy afectadas). El diseño fue en bloques al azar con 3 repeticiones y pruebas de Shapiro-Wilks y Friedman. Se observaron diferencias altamente significativas en eficacia de control entre los herbicidas evaluados en preemergencia, en ambas fechas de medición. S-metolacloro controló 66% de malezas, Linuron 82% y Pendimetalin 89%, sin causar fitotoxicidad en plantas de alcaucil. Oxifluorfen controló 93%, con fitotoxicidad 3 en la primera medición y de 2 en la segunda. Si bien la Prometrina controló 83%, la fitotoxicidad fue de 4. Se observaron diferencias altamente significativas en tratamientos posemergencia en la segunda fecha de medición en Eleusine, Digitaria y Echinocloa. Linuron controló el 93,7% con fitotoxicidad 3 en ambas fechas. Prometrina el 92% con fitotoxicidad de 4. En las condiciones del experimento, los herbicidas destacados fueron Pendimentalin y Linuron en preemergencia.

Effect of soybean crop structure on large crabgrass (Digitaria sanguinalis) growth and seed dormancy

Crop-weed interactions are affected by the environment alterations resulting from the crop presence, such as modifications in temperature, light quality and quantity and moisture conditions that could modify the weed performance. The objectives of this work were to study 1) how soybean [Glycine max (L.) Merr.] crop structure modifies the environment under the canopy and large crabgrass [Digitaria sanguinalis (L.) Scop.] plant structure, biomass and seed production and dormancy and 2) the relative importance of these environmental changes on the weed characteristics. A field experiment in a completely randomized block design with five replicates was performed to evaluate narrow and wide inter-row spacing, and soybean maturity group III and IV. Measured variables were intercepted solar radiation (RAD), R-FR ratio, humidity, minimum, maximum and alternating temperatures, as well as, weed biomass, tillers per plant, weed height and seed dormancy. Crop canopy reduced solar radiation, R-FR ratio, daily average maximum and alternating temperatures. Soybean presence reduced the weed biomass, tillers and seeds per plant and seed dormancy. High solar radiation intercepted by the crop during the reproductive phase was the main environmental variable related to reductions in weed biomass, tillers per plant and fecundity. The combination of low temperature and solar radiation received by developing seeds was more related to seed dormancy than the rest of the variables. Crop management decisions focused on the fact that keeping the crop canopy alive during more time by the end of the season, would not only reduce the weed growth but also seed dormancy.

Obtención de la primera variedad argentina de mostaza india: SANTA CATALINA UNLP, para su utilización como biofumigante

En las últimas décadas, la mayor concientización de la sociedad sobre los efectos nocivos de los agroquímicos sobre la salud y el medio ambiente, ha generado cambios en algunas explotaciones hortícolas y florícolas del cinturón verde de Buenos Aires, que han incorporado otras estrategias de control de plagas, amigables con el medio ambiente, reduciendo el uso de plaguicidas sintéticos. En este contexto, la biofumigación con mostaza india (Brassica juncea L. Czerniak) se presenta como una táctica biológica eficaz para el control de plagas de suelo, que podría formar parte de un programa de manejo agroecológico de plagas. En nuestro país hay registros de prácticas de biofumigación con recursos locales (principalmente, restos de cosecha de especies hortícolas brassicáceas), pero no existían desarrollos de cultivares con propósitos biofumigantes. Por este motivo, se realizó un proceso de selección masal y se obtuvo la variedad biofumigante SANTA CATALINA UNLP, que es el primer cultivar de mostaza india inscripto en el Registro Nacional de Cultivares del INASE. La variedad de mostaza india SANTA CATALINA UNLP fue desarrollada para su utilización como biofumigante de suelos y sustratos en producciones hortícolas y florícolas. Dado que el proceso de selección se realizó en la localidad de Llavallol, conurbano bonaerense, este cultivar se adapta a las condiciones medioambientales del cinturón verde de Buenos Aires. Numerosas investigaciones realizadas durante el período de selección del cultivar, han demostrado que la biofumigación con esta variedad es eficaz para suprimir algunas especies de hongos fitopatógenos, reducir poblaciones de nematodos fitófagos y para inhibir la emergencia y el crecimiento de algunas malezas. También se demostró que la biofumigación con mostaza india no afecta al hongo antagonista Trichoderma spp. ni a los nematodos de vida libre del suelo (benéficos). La variedad SANTA CATALINA UNLP fue desarrollada en el Instituto Fitotécnico de Santa Catalina, dependencia de la Facultad de Ciencias Agrarias y Forestales de la Universidad Nacional de La Plata. Desde el año 2009 hasta el 2016 se realizó selección masal sobre una población mixta proveniente de un lote de semillas de mostaza india que ingresó al país procedente de la India, para ser comercializado como condimento. Se seleccionaron las plantas con mayor biomasa aérea y con menor incidencia y severidad de podredumbre negra o mancha en V (Xanthomonas campestris pv. campestris). Paralelamente se realizaron ensayos para evaluar su capacidad como biofumigante para el biocontrol de plagas agrícolas. En junio de 2017 fue multiplicada, verificándose la estabilidad de la variedad. En varios ensayos se observó que la biofumigación con mostaza india tuvo efecto supresor sobre el crecimiento de Fusarium graminearum cultivado in vitro. En otro trabajo se concluyó que la biofumigación redujo significativamente la cantidad de esclerocios de Sclerotium rolfsii. Los resultados obtenidos en varios ensayos mostraron que la técnica de biocontrol con el hongo antagonista Trichoderma spp. puede ser considerada compatible con la biofumigación con B. juncea. Además, el crecimiento del hongo benéfico Trichoderma spp. no fue afectado por la biofumigación con B. juncea. En otro ensayo se observó que la biofumigación con dosis bajas B. juncea no inhibió el crecimiento in vitro de colonias de Azospirillum brasilense, bacteria rizosférica promotora del crecimiento vegetal. Con respecto al efecto de la biofumigación sobre las malezas, se observó reducción del crecimiento de varias especies de malezas: Anoda cristata (malva cimarrona), Picris echiodes, Portulaca oleracea (verdolaga), Digitaria sanguinalis (pasto de cuaresma) y Taraxacum officinalis (diente de león). También se determinó que la biofumigación con SANTA CATALINA UNLP incrementó la densidad de nematodos de vida libre y redujo la densidad de nematodos parásitos de plantas.

ADDITIONS TO THE VASCULAR PLANT FLORA OF THE REPUBLIC OF MORDOVIA (RUSSIA): CONTRIBUTION OF THE iNATURALIST PLATFORM

"The (re)check of the iNaturalist data related to the Republic of Mordovia (European Russia) allowed us to find 16 vascular plant species, considered to be new taxa for the vascular plant flora of this region, in comparison to Silaeva et al. (2010). These species are Nonea rossica, Erigeron strigosus, Medicago × varia, Dianthus chinensis, Symphytum × uplandicum, Lamprocapnos spectabilis, Petunia × atkinsiana, Oenothera villosa, Parthenocissus inserta, Reynoutria × bohemica, Eschscholzia californica, Quercus rubra, Digitaria sanguinalis, Lysimachia punctata, Acer ginnala and Stachys byzantina. In addition, we present new data about the distribution of the five species (Silene wolgensis, Amaranthus cruentus, Cruciata laevipes, Euphorbia cyparissias and Achillea leptophylla) found in the Republic of Mordovia since publication of Silaeva et al. (2010). A majority of the species under discussion are alien plants arrived in Mordovia accidentally or considered as cultivated plants escaping in the wild. Taking into account the newly revealed species, the vascular plant flora of the Republic of Mordovia currently includes 1464 species. In this study, we highlight again the relevance and feasibility of the use of the iNaturalist platform, as an effective tool for the study and monitoring of regional and national biodiversity."