R6siim£: ZusammenfassungAnnual applications of the herbicides atrazine, simazine, linuron and diuron at 4 5 kg/ha were made to the same plots for 9 consecutive years from 1963 to 1971 in a peach {Prunus persica (L.) Batsch.) orchard located on sandy loam soil near Harrow, Ontario. Soil samples from these plots were collected in late October for the last 3 years (1969)(1970)(1971) and trees were cut down in December, 1969. Herbicide residues were determined by bioassays based on the fresh and dry weight of oats {Avena sativa L.) and in one year results were confirmed by chemical analysis. Significant accumulation of herbicides was not observed. The maximum residue levels measured in October over the 3 years of sampling were 7'3 kg/ha for diuron, 3-8 kg/ha for linuron, 1 -6 kg/ha for simazine and 0 4 kg/ha for atrazine in the top 15 cm ofthe soil profile. Simazine and atrazine showed a rapid decrease in amount after treatment but diuron and linuron were degraded more slowly. Measurable residues of all herbicides were confined to the upper 15 cm of the soil profile and the majority of herbicide remained in the 0-5-cm soil layer. Oats were planted in the orchard plots from 1972 to 1974 to follow the disappearance ofthe herbicides. All herbicides caused highly significant yield decreases in 1972, atrazine causing the least (38%) and diuron the greatest (86%) reductions. Diuron reduced the yield of oats in 1973 and caused a highly significant decrease in the weight of young oat plants in 1974. Rhidus d'atrazine, de simazine, de linuron et de diuron apris des applications annuelles ripetees dans un verger de pechers.Des applications annuelles avec les herbicides suivants: atrazine (2-chloro-4-6thyIamino-6-isopropylamino-l,3,5-triazine), simazine (2-chloro-4,6-bis6 thylamino-1,3,5-triazine), linuron (Ar'-(3,4-dichloroph6nyl)-Af-m6thoxy 7V-m6thylur6e) et diuron (Af'-3,4-dichloroph^nyl)-A'Af-dim^thyIur6e) i 4,5 kg/ha, ont tit faites sur les memes parcelles pendant neuf annees cons6cutives, de 1963 a 1971, dans un verger de pechers {Prunus persica (L.) Batsch.), implant6 dans un sol de • Present address: Research Branch, Agriculture Canada, Ottawa, Ontario, Kl A 0C6.

In a 3-year study, one annual application of a 10% granular formulation of disulfoton in the soil at a rate of 2 lb actual toxicant per acre controlled M. persicae throughout the entire period that aphids were most prevalent in pepper fields. Some control was observed within a few days of treatment, but effective control did not occur until 2 to 3 weeks after placement of the insecticide. Irrigation increased the initial uptake of disulfoton, but after 2 weeks the degree of control was essentially the same in irrigated and nonirrigated plots.Analyses of fruit samples from treated plots showed that there were no detectable amounts of disulfoton or its oxidation products 42, 50, and 60 days after treatment. These observations suggest that the required interval of 90 days between treatment and harvest could be reduced. Appreciable amounts of the insecticide or its oxidation products were present in the leaves on all sampling dates.

Residues of the ethylenbisdithiocarbamate (EBDC) fungicides maneb and mancozeb on tomato fruits ranged between 0.03 and 0.80 ppm (mean 0.31 ppm) when field crops were sprayed five or eight times at intervals of 3–4 days. Ethylenethiourea (ETU) was detected only in one sample, at 0.03 ppm. In canned juice made from whole fruit, EBDC levels ranged from non-detectable to 0.62 ppm (mean 0.31 ppm) and ETU levels from non-detectable to 0.07 ppm (mean 0.02 ppm). These levels were generally higher than in canned peeled fruit where the range of EBDC was from non-detectable to 0.27 ppm (mean 0.09 ppm) and of ETU from non-detectable to 0.05 ppm (mean 0.01 ppm). On greenhouse tomatoes, two or four sprays with mancozeb resulted in residues of up to 2.81 ppm EBDC (mean 0.714 ppm) and 0.08 ppm ETU (mean 0.0097 ppm) on the fruit. All levels of EBDC were below the Canadian tolerance level of 4 ppm but ETU is unacceptable in food in Canada.

No abstract

No abstract