Variation in amount and composition of epicuticular wax among several apple (Malus ×domestica Borkh.) cultivars was characterized by gas chromatography, thin-layer chromatography, and gas chromatography-mass spectroscopy. Across cultivars, wax mass ranged from 366 to 1038 μg·cm-2. Wax mass decreased during the 30 days before harvest. Ursolic acid accounted for 32% to 70% of the hydrocarbons that make up the epicuticular wax. Alkanes, predominantly 29-carbon nonacosane, comprised 16.6% to 49%. Primary alcohols of the hydrocarbons ranged from 0% to 14.6% of the epicuticular wax. Secondary alcohols of the hydrocarbons were the most cultivar specific, making up 20.4% of the epicuticular wax in `Delicious' and only 1.9% `Golden Delicious' strains. Aldehydes and ketones of the hydrocarbons represented a small amount of total wax, ranging from 0% and 6.0%. Percentage of primary alcohol in the epicuticular wax increased as fruit developed. Other components showed no distinct trends with fruit development. Examination of the ultrastructure of cuticular wax using scanning electron microscopy revealed structural differences among cultivars.

Herbicide soil/solution distribution coefficients (Kd) are used in mathematical models to predict the movement of herbicides in soil and groundwater. Herbicides bind to various soil constituents to differing degrees. The universal soil colloid that binds most herbicides is organic matter (OM), however clay minerals (CM) and metallic hydrous oxides are more retentive for cationic, phosphoric, and arsenic acid compounds. Weakly basic herbicides bind to both organic and inorganic soil colloids. The soil organic carbon (OC) affinity coefficient (Koc) has become a common parameter for comparing herbicide binding in soil; however, because OM and OC determinations vary greatly between methods and laboratories, Koc values may vary greatly. This proposal discusses this issue and offers suggestions for obtaining the most accurate Kd, Freundlich constant (Kf), and Koc values for herbicides listed in the WSSA Herbicide Handbook and Supplement.

Experiments were conducted in North Carolina in winter/spring 1992, 1993, and 1994 to determine crop tolerance, weed response, and clopyralid residue levels in fruit of ‘Chandler’ strawberry plants treated with clopyralid. Clopyralid at 0.07, 0.14, 0.20, or 0.28 kg ai ha−1applied POST over strawberry plants and vetch resulted in 100% control of vetch species, 49 to 83% control of black medic, and less than 6% crop injury. As a comparison, 2,4-D at 0.84 kg ai ha−1applied POST at 5 to 10% strawberry bloom resulted in 50% control of black medic and 48 to 73% crop injury, while 2,4-D at 0.84 kg ai ha−1applied POST to 7- to 9- and 9- to 10-leaf strawberries resulted in 5 to 22% crop injury and no adverse affect on strawberry yield. Single applications of clopyralid at 0.07, 0.14, or 0.28 kg ai ha−1applied POST to weed-free strawberries at the 5- to 6-, 6- to 7-, 9- to 10-, or 12- to 14-leaf stage caused less than 6% injury and did not adversely affect strawberry yield. In 1993 with preharvest intervals (PHI) of 39, 66, and 101 d after treatment all clopyralid residue levels in strawberry fruit were below the detectable level of 0.3 parts per billion (ppb). In 1994, with PHI of 30, 59, and 87 d after treatment trace clopyralid residues were found in strawberry fruit with a range from 0.25 to 1.9 ppb, with a level of detection of 0.2 ppb.

The Piedmont region in the southeastern USA is characterized by sloping, crust-prone soils conducive to runoff losses of agricultural chemicals. Three tillage-residue management systems were compared for their effect on concentrations of atrazine [2-chloro-4-ethylamino-6isopropylamino-l,3,5-triazine], metolachlor [2-chloro-N-(2-ethyl-6methylphenyl)-N-(2-methoxy-l-methylethyi) acetamide], and bromide in surface runoff and in the soil profile of a Pacolet sandy clay loam (clayey, kaolinitic, thermic Typic Kanhapludults). These systems included conventional tillage (CT), no-tillage grain production with corn (Zea mays L.) residue (NTG), and no-tillage silage production without residue (NTS). The first simulated rainfall event consisted of a low (1.27 cm h-~) or high (5.08 cm -z) rainfall r ate a pplied f or 30 min following herbicide and bromide application. One week later, the high rate was simulated on all plots. The CT treatment generally produced less surface runoff, and accompanying lower chemical concentrations, compared with both no-tillage treatments on the first date. Runoff differences due to tillage system were less on the second date because of surface sealing processes under CT. Averaged over 2 yr, the percentage of applied atrazine lost on the first runoff event was 6.2% for NTG, 4.4% for NTS, and 1.5% for CT. Losses of atrazine in runoff on the second date were 1.5, 1.4, and 1.0% of that applied for NTG, NTS, and CT, respectively. The surface 7.5 cm of soil contained the highest concentrations of chemicals for all treatments, with treatment differences occurring primarily in the surface 0 to 15 cm of soil. Lower runoff values under CT generally resulted in higher soil chemical concentrations.

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