Sensitivity of 49 tomato cultivars and four weeds to DPX-E9636 was determined in greenhouse experiments. Cultivar tolerance varied from completely tolerant to intolerant. The most efficacious application method in greenhouse experiments was early POST for the weeds tested (yellow nutsedge, prostrate eclipta, and paraquat-resistant and -sensitive American black nightshade). Paraquat-resistant American black nightshade was 123 times more sensitive to DPX-E9636 than the paraquat-sensitive biotype. Under field conditions and at 0, 36, or 72 g ai/ha applied one week after transplanting, tomato cultivars showed no response to DPX-E9636 in visual vigor ratings 3 wk treatment, or in shoot fresh or dry weight 4 wk after treatment.

Eight accessions of weedy nightshades representing five species were evaluated for response to four herbicides applied preemergence in growth chamber studies and four herbicides applied postemergence in greenhouse studies. Species differed in susceptibility to all herbicides evaluated. The largest differences were found with postemergence applications of chlorsulfuron {2-chloro-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]benzenesulfonamide}; hairy nightshade (Solanum sarrachoides Sendt. ♯ SOLSA) was relatively susceptible, but eastern black nightshade (S. ptycanthum Dun.) was very tolerant. S. ptycanthum, however, was one of the more susceptible species. It was always more susceptible than black nightshade (S. nigrum L. ♯ SOLNI) to all other herbicides evaluated.

Leaves of torpedograss and American black nightshade were extracted with chloroform at room temperature. A 2-s dip was sufficient to remove most of the epicuticular wax from torpedograss. However, epicuticular hydrocarbon weight represented only 6.4% of the total extract weight and 6.94 μg g−1 fresh weight of chlorophyll were found in the 2-s extract. This represented 25% of the chlorophyll detected in the 232-h extract. In American black nightshade, epicuticular hydrocarbons continued to be removed from the leaf surface up to 6 h of extraction. Epicuticular hydrocarbons represented 0.6% of total extract weight. In the 6-h extract, 4.02 μg g−1 fresh weight of chlorophyll were found. This represented 17% of the chlorophyll detected in the 232-h extract. Evaluation of leaf surfaces using scanning electron microscopy indicated that epicuticular wax was being removed from torpedograss leaves up to 1 h. However, there was little visible evidence for wax extraction from the surface of American black nightshade leaves.

Information from taxonomic treatments and comparisons of accessions from numerous locations grown in the field and greenhouse were combined and summarized to produce a key and descriptions of common agricultural nightshades in North America (Solanum americanum Mill., S. nigrum L., S. ptycanthum Dun., and S. sarrachoides Sendt.). Quantitative and qualitative descriptions of key characters and photographs of important morphological structures are provided to facilitate field identification. Problems with nomenclature among these species are discussed, and a system of common names that would standardize usage is proposed.