The external surfaces and internal structures of particles of milled pine bark (Pinus taeda L. and P. elliottii Engelm.) were examined with scanning electron microscopy. Numerous external openings, cracked cell walls and internal cellular connections, that might allow water penetration were observed. Periderm surfaces were without pores, and contained rough surfaces and apparently waxy substances that might resist water penetration or absorption.
Water absorption curves were developed for air dry peat-vermiculite and pine bark media. Data indicated 70-78% of moisture saturation was attained within 5 days with a peatvermiculite medium while 48 days were required to achieve 58-70% saturation with a milled pine bark medium. Increased water absorption of pine bark after 10 days of wetting suggested that a threshold moisture level within the bark particles is necessary if water uptake is to be enhanced. The threshold moisture content was established at 35% (wet wt basis).
Managers of greenhouses used in vocational training or therapeutic programs often face pesticide use restrictions due to medical safety codes, possible sensitivity due to client medications, frequent presence of patient groups, or the added risk of exposure to clients with limited awareness. This review of three horticultural therapy programs emphasizes the practice of preventive measures, manual controls, and limited chemical methods to discourage pest problems and outlines pest control strategies that may not be feasible in commercial greenhouses. The importance and application of integrated pest management and biological pest controls are discussed. Procedures and client activities for sanitation, cultural controls, pest monitoring, and safe application of spray solutions are presented. Client work habits and skills may be developed using the tasks suggested for pest control, and various skill competency levels may be incorporated into the management scheme. The need for client training and task accomplishment may encourage alternative labor-intensive pest-control methods in therapeutic greenhouses.
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