Lilacs (Svringa vulgaris L. and other spp.) at 6 locations in Northeastern United States were evaluated over several years for their sensitivity or resistance to urban-generated pollutants responsible for the leaf roll-necrosis disorder. Twenty-three cultivars were classified as slightly injured, 71 were moderately injured, and 5 were severely injured. S. vulgaris cultivars were more sensitive than non-S. vulgaris and interspecific hybrids.
A growth equation and a yield relationship were calculated to estimate space requirements and yields of two pecan cultivars (Carya illinoensis (Wangenh.) C. Koch]. The resulting estimates were used with pruning cost estimates in a simulation model to determine the orchard space management practice that maximizes income over time. The income maximizing spacings were 10.7 × 10.7 m and 13.7 × 13.7 m for the precocious ‘Desirable’ and the non-precocious ‘Stuart’, respectively. Annual pruning after the canopy closed produced the highest income for both cultivars.
Pesticides have been the primary method of pest control for years, and growers depend on them to control insect and disease-causing pests effectively and economically. However, opportunities for reducing the potential pollution arising from the use of pesticides and fertilizers in environmental horticulture are excellent. Greenhouse, nursery, and sod producers are using many of the scouting and cultural practices recommended for reducing the outbreak potential and severity of disease and insect problems. Growers are receptive to alternatives to conventional pesticides, and many already use biorational insecticides. Future research should focus on increasing the effectiveness and availability of these alternatives. Optimizing growing conditions, and thereby plant health, reduces the susceptibility of plants to many disease and insect pest problems. Impediments to reducing the use of conventional pesticides and fertilizers in the environmental horticulture industry include 1) lack of easily implemented, reliable, and cost-effective alternative pest control methods; 2) inadequate funding for research to develop alternatives; 3) lack of sufficient educational or resource information for users on the availability of alternatives; 4) insufficient funding for educating users on implementing alternatives; 5) lack of economic or regulatory incentive for growers to implement alternatives; and 6) limited consumer acceptance of aesthetic damage to plants. Research and broadly defined educational efforts will help alleviate these impediments to reducing potential pollution by the environmental horticulture industry.