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The severity of drought is increasing owing to global climate change. Knowledge about the influence of drought on weeds and herbicide performance is necessary for optimising herbicide applications. Therefore, dose-response trials were conducted to investigate the influence of drought stress on the efficacy of four herbicides.Drought-stressed and non-stressed Hordeum spontaneum seedlings were exposed to nine doses of sulfosulfuron and sulfosulfuron + metsulfuron-methyl. Clodinafoppropargyl and mesosulfuron-methyl + iodosulfuron-methyl sodium were applied to drought-stressed and non-stressed seedlings of Avena sterilis subsp. ludoviciana. Leaf greenness index (SPAD), total chlorophyll content, stomatal conductance and photosynthesis rate of both species were measured. The efficacy of herbicides on H. spontaneum was not influenced by drought stress. In contrast, the performance of herbicides on A. sterilis subsp. ludoviciana was reduced under drought stress, where the ED 50 increased by 1.5-fold. The low doses (<2.2 g a.i. ha −1 ) of mesosulfuronmethyl + iodosulfuron-methyl-sodium caused hormesis on A. sterilis subsp. ludoviciana. Total chlorophyll content and SPAD index of both species increased due to drought stress. The stomatal conductance and photosynthesis rate of A. sterilis subsp. ludoviciana decreased under drought stress, while H. spontaneum was not influenced. The lack of detrimental effect of drought stress on sulfosulfuron and sulfosulfuron + metsulfuron-methyl performance might be attributed to similar stomatal conductance and photosynthesis rate of the drought-stressed and non-stressed H. spontaneum. The performance reduction in herbicides on drought-stressed A. sterilis subsp. ludoviciana might be owing to the reduction in stomatal conductance and photosynthesis rate. Using adjuvants, diverse formulations and early application of herbicides were suggested for future research to hamper the negative effect of drought on herbicides.

-Swiss farmers nowadays gain a great part of their income from ecological compensation areas, especially wildflower strips, instead of cash crops. Mainly Crisium arvense and invasive alien plant species such as Solidago ssp. are abundant in ecological compensation areas; Reynoutria ssp. is highly abundant in non-agricultural zones and increasingly abundant in agricultural fields; Ambrosia artemisiifolia is an annual weed in agriculture and mandatory to control in Switzerland. Here, we present the results of a survey of wildflower strips in ecological compensation areas. The results of field and pot trials with Solidago, Reynoutria and Ambrosia species are also presented, as well as strategies for Ambrosia control and the information campaign on Ambrosia in Switzerland. The major result we found that was that wildflower strips are infested by noxious weeds and invasive alien plant species. Infestation is in most cases not as alarming as it is sometimes presented in the daily press. Solidago, Reynoutria and Ambrosia species cannot always be fully killed by one control measure. A check of efficacy and repeated control is necessary to achieve complete killing. Abundance of these species in non-agricultural zones makes weed control methods subject to public discussions. The main outcome of the work with weed species interfering in agricultural and non-agricultural zones is the conclusion that guidelines are needed to concentrate financial and human resources on real problems such as public health or damage to infrastructure. Three elements -a collection of weak point sheets for noxious endemic and exotic weed species, a detailed list of costs for control methods, and a detailed list of restrictions for use of control methods in environmental zones, both adapted to a country or region -would allow any functionary in any region to choose adequate control methods.invasive plants / weed control / Reynoutria / Solidago / Ambrosia

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