Effects of salinity and desalination on seed germination of six annual weed species

The effects of various salinities and desalination on seed germination of six annual glycophytes （Artemisia sieversiana, A. scoparia, Chloris virgata, Eragrostis pilosa, Chenopodium acuminatum and Chenopodium glaucum） were studied in Horqin Sandy Land, Inner Mongolia, China. NaCl solutions of five concentrations （0 mM, as the control, and 50, 100, 200 and 300 mM） were used for saline stress and desalination treatments. Increasing salinity significantly reduced germination percentages of A. sieversiana, A. scoparia, Ch.virgata and Ch. acuminatum, but had no effect on the germination percentages of E. pilosa. Lower salinity levels （50 mM） significantly increased germination percentage of Ch. glaucum. High salinity might be a precondition for germi- nation after desalination for five of the six species, excepting E. pilosa at NaCl concentration of 300 mM in comparison with non-primed seeds. Higher salinity （200 mM） led to some specific ion toxicity and reduced seed viability of A. sieversiana. No specific ion toxicity but an osmotic effect limited the germination of other five species was observed The final germination percentages （salinity stress and desalination） of the six species showed three variations in comparison with the controls, namely, indiscrimination, stimulation, and reduction. Germination responses to salinity and desalination suggested that the six species were separated into three categories. Three species （A. sieversiana, Ch. virgata and Ch. acuminatum） showed similar germination responses to salinity with those of halophyte, but also showed a lower tolerance limit than most halophytes, although this was not always the case. A. scoparia and Ch. glaucum exhibited some ‘salt stimulation’ in seed germination percentages after desalination, whereas E. pilosa did not show any obvious responseto salinity. Therefore, salinity usually induces dormancy of seeds with strong germination capacity in fresh water, but has few, or even positive, effects on seeds with strong innate dormancy.

Weed Management in Azuki Bean with Postemergence Herbicides

A limited number of postemergence (POST) herbicides are available for weed management in azuki bean production in Ontario. A total of three field trials were conducted during 2017 to 2019 at the Huron Research Station, University of Guelph, Exeter, Ontario, Canada to evaluate the efficacy of various postemergence (POST) herbicides for weed control in azuki bean. Fomesafen, acifluorfen and acifluorfen + Assist® caused up to 6% crop injury and weed interference reduced azuki bean yield up to 42%. Bentazon, bentazon Forte, bentazon/acifluorfen, bentazon + fomesafen + Assist®, bentazon + fomesafen + Turbocharge® and bentazon Forte + fomesafen caused up to 16% injury and weed interference reduced azuki bean yield up to 53%. Fomesafen, acifluorfen, acifluorfen + Assist®, bentazon, bentazon Forte, bentazon/acifluorfen, bentazon + fomesafen + Assist®, bentazon + fomesafen + Turbocharge® and bentazon Forte + fomesafen provided 36% to 88% control of redroot pigweed (Amaranthus retroflexus L.), common ragweed (Ambrosia artemesiifolia L.), and common lambsquarters (Chenopodium album L.). Fomesafen, acifluorfen + Assist® and acifluorfen provided 59% to 83% control of flower-of-an-hour (Hibiscus trionum L.), but bentazon, bentazon Forte, bentazon/acifluorfen, bentazon + fomesafen + Assist®, bentazon + fomesafen + Turbocharge® and bentazon Forte + fomesafen provided 78% to 99% control of H. trionum. All POST herbicides evaluated provide 99% to 100% control of wild mustard (Sinapis arvensis L.) in azuki bean. Based on these results, none of the POST herbicide evaluated that included bentazon can be used safely for the control of annual broadleaved weeds in azuki bean under Ontario environmental conditions.

Comparative Efficacy of Common Broad Leaf Herbicides against an Invasive Weed: <i>Parthenium</i><i>hysterophorus</i>L.

Parthenium hysterophorus L. (parthenium weed) is an annual weed that grows rapidly in disturbed land. It is considered as one of the most hazardous weeds in Pakistan as it poses serious health problems to livestock as well as severe allergenic reactions in humans. It has invaded the Punjab and Khyber Pakhtunkhwa provinces and also been spreading in other parts of the country where it poses a risk for the grazing lands, roadsides, forests, wet lands, waste lands and of all types of cropped and non-cropped areas in Pakistan. The present studies were carried out to determine the impact of four locally available broad leaf herbicides viz;Stomp 455 CS (pendimethalin), Buctril Super 60 EC (bromoxynil + MCPA), Vantage 48 SL (glyphosate) and Logran Extra 750 WG (triasulfuron + terbutryn) (@ recommended and ½ of recommended dose) against P. hysterophorus grown in pots at research field of CABI CWA, Rawalpindi. All herbicides were applied at three growth stages (rosette, bolted and flowering). The observations for the mortality of P. hysterophorus were made 2 and 4 weeks after spray. The glyphosate was the most effective and reported 100% mortality of P. hysterophorus plants at flowering stage followed by bromoxynil + MCPA (89%), pendimethalin (80%) and triasulfuron + terbutryn (61%) at recommended dose after 4 weeks of spray. All tested herbicides achieved a mortality between 38% - 86% at rosette while 54% - 96% mortality at bolted stage after 4 weeks. Initially, 2 weeks after spray at flowering stage glyphosate caused 53% wilting followed by 49% (bromoxynil + MCPA), 33% (pendimethalin) and 9% (triasulfuron + terbutryn) at their recommended doses. The results indicated that P. hysterophorus is the most susceptible to glyphosate and bromoxynil + MCPA, both these herbicides are very promising for the wilting and management of parthenium weed.