The phytotoxic effect of herbicides applied post-emergence was investigated in a herbicide sensitivity experiment set up on parental maize genotypes in Martonvásár. A total of 48 Martonvásár inbred lines and 12 single line crosses were included in small-plot experiments set up in two replications. Ten herbicides were applied at the normal a...uthorised rate and at twice this quantity. Compounds intended for pre-emergence application were applied when maize was in the 3–4-leaf stage and post-emergence herbicides in the 7–8-leaf stage of development. The extent of phytotoxicity was scored two weeks after treatment. Some of the herbicides tested are not authorised for use in seed production fields, but it is important to know how the parental genotypes respond to all types of herbicides. Phytotoxic symptoms of varying intensity were only observed on a third of the 60 parental genotypes examined; the majority of the lines exhibited no reaction to any of the herbicides. Averaged over the 60 genotypes the level of phytotoxic damage was less than 10% for the single dose. When the double dose was applied somewhat more severe damage was induced by products containing Mesotrione + Nicosulfuron or Foramsulfuron + Isoxadifen-ethyl, but this was still below 15%. The herbicide dose had a three times stronger influence on the intensity of the symptoms than the type of herbicide. With the exception of Topramezone, there was a significant difference between the effects of the normal and double doses. The greatest dose effect differences, in decreasing order, were observed for Mesotrione + Nicosulfuron, Foramsulfuron + Isoxadifen-ethyl. Nicosulfuron and Mesotrione + Terbutylazine. The Mesotrione + Terbutylazine active ingredient combination only caused mild (<10%) symptoms on a total of 11 genotypes, while the Mesotrione + Nicosulfuron combination induced more severe phytotoxic symptoms on 26 lines. When Nicosulfuron was applied alone it caused milder symptoms on fewer genotypes than in combination with Mesotrione. Among compounds of the sulphonyl-urea type, the least severe symptoms on the fewest genotypes were recorded in the case of Prosulfuron.
Field experiments were conducted to study affects of pH and hardness of spray water on efficacy of a herbicide combination (terbuthylazine + mesotrione) influenced by several pH adjusters and adjuvants in Debrecen, Hungary in 2008, 2009 and 2010. Favourable or unfavourable effects of pH and hardness of spray water could be observed under field...conditions. Evaluation of weed control efficacy is suitable for examination of affects of spray water pH and hardness on herbicides. The terbuthylazine and mesotrione herbicide combination is suitable to control monocotyledonous and dicotyledonous weed species, however, significant effects of hardness and pH of spray carrier was observed only in control of monocotyledonous weeds. Certain pH adjusters (e.g. ammonium nitrate) can lessen harmful affects of water hardness effectively. Significant loss of efficacy of sensitive herbicide was found in hard water (by about 50-60%), and surfactants was not able to eliminate that harmful affect. However, biological activity was the same as in soft water with ammonium nitrate which can overcome the antagonism of salts. That pH adjuster had a more significant affect on the efficacy of the herbicide than the surfactant had in that experiment.
The herbicide tolerance levels of 49 Martonvásár inbred parents were examined in Martonvásár in a herbicide susceptibility trial in 2016. The normal dosage recommended in the permit documentations and double dosage were used for the 12 small-plot herbicide treatments performed in two repetitions. Spraying of early post-emergent herbicides w...as carried out in the 1–2-leaf stage, while post-emergent treatments were applied in the 7–8-leaf stage of maize. The extent of phytotoxicity was scored for the early post-emergent herbicides two and four weeks after treatments and for the post-emergent herbicides two weeks after treatments, respectively. Some of the herbicides examined are not approved in seed production; however it is important to know the reaction of maize parent genotypes for every type of herbicides. The active agent topramezone was withdrawn from the market in 2015, but it was included in the trials as its usage was allowed until stocks run out in 2016. The herbicide agents were examined as follows: mesotrione + S-metolachlor + terbutylazine; isoxaflutol + tiencarbazon methyl + cyprosulfamide; isoxaflutol + cyprosulfamide; mesotrione + terbuthylazine; tembotrione + isoxidifen-ethyl; mesotrione + nicosulfuron; prosulfu ron; nicosulfuron +prosulfuron + dicamba; bentazone + dicamba; nicosulfuron; topramezone; foramsulfuron + isoxadifen-ethyl.
Among early post-emergent herbicides, isoxaflutol + cyprosulfamide caused the less phytotoxic damage in the genotypes. The large amount of precipitation during the spring facilitated the infiltration of the active ingredient S-metolachlor, used regularly and successfully also in seed production, into the root zone, resulting in phytotoxic symptoms on susceptible inbred lines at the time of the first inspection. These genotypes recovered by the end of the vegetation period. The spring weather was cooler than usual, retarding the development of maize and thus led to the slower fermentation of herbicide active ingredients, accordingly, all of the post-emergent herbicides caused visible phytotoxic symptoms on some of genotypes. The most severe damages were generally caused by the double dosage of nicosulfuron + prosulfuron + dicamba, nicosulfuron, and foramsulfuron + isoxadifen-ethyl.
The phytotoxic effects of herbicides applied pre-, early post- and post-emergence were studied in maize in a herbicide sensitivity experiment were set up in Martonvásár and Törökszentmiklós. The herbicides were applied in normal and in double doses to 37 Martonvásár inbred lines and to six parental single crosses. The small-plot experime...nts were set up in two replications. The wet weather that followed the pre- and early post-emergence treatments promoted the appearance of phytotoxic symptoms on maize. The degree of phytotoxicity was recorded on the 14th day after post-emergence treatment and on the 14th and 28th days after the pre- and early postemergence treatments. Herbicides applied pre-emergence only caused slight symptoms on maize. Although the double dose increased the damage, it was still not more than 5% on average. The symptoms caused by herbicides applied in the early post-emergence stage were more intensive than those detected in the pre-emergence treatments. However, the damage caused by the double dose of isoxaflutol + thiencarbazone-methyl and by the split treatment with nicosulfuron remained below 10%. The symptoms became somewhat more severe at the 2nd scoring date. Among the post-emergence treatments the maize genotypes had the least tolerance of the mesotrione + nicosulfuron combination of active ingredients, where the double quantities resulted in 13–14% damage in average.
The tolerance of 15 inbred maize lines grown on chernozem soil with forest residues in Martonvásár was tested against herbicides applied post-emergence in two dry, warm years (2003 and 2011) and in two cool, wet years (2004 and 2010). The herbicides mesotrione + terbutylazine, nicosulfuron and dicamba were applied to maize inbred lines in the... 7–8-leaf stage at the maximum dose authorised for practical use and at double this rate. The plants were scored for the intensity of visible phytotoxic symptoms 14 days after treatment.
The level of phytotoxicity observed in dry, warm years was 5.14%, averaged over the lines, herbicides and rates. The intensity of visible symptoms was almost 2.5 times as great in cool, wet years (12.76 %).
Averaged over the four years, the lines and the rates, the least damage was caused by dicamba (5.77 %), followed by mesotrione + terbutylazine (7.23 %). The most severe symptoms were induced by nicosulfuron (16.17 %). This could be attributed to the fact that some of the inbred lines were extremely sensitive to herbicides, especially those of the sulfonylurea type.
A difference of more than 1.5 times was observed between the two doses, but the correlation between the concentration and the severity of the visual symptoms was not strictly linear. Compared to the normal dose (100 %) the double rate resulted in a 162.5% increase in symptom severity. In most cases plants treated with the normal dose were symptom-free or only exhibited a low level of phytotoxicity.