Vegetative propagules of sago pondweed (Potamogeton pectinatus L.) and American pondweed (P. nodosus Poir.) grown under a 14-hr photoperiod of light varying in chromatic composition produced plants with longer internodes and more extensive shoot and stolon development under red light than under blue. Pondweeds grown for 4 weeks under 25 to 400 ft-c of light made progressively more growth at the higher light intensities. Plant weight, branch number and stolon development increased while shoot length and shoot-root ratio decreased with increased light. Pondweeds grown under each of 5 light intensities at temperatures of 60, 70, or 80 F were treated with emulsified xylene or alkyl tolyl methyl trimethyl ammonium chloride. Pondweeds cultured at the higher light intensities and higher temperatures were progressively more injured. Injury from treatment with either herbicide increased with age and plant maturity from early vegetative to flower-bud stage. Equivalent injury was produced on plants of equivalent maturity regardless of chronological age. Pondweeds cultured under 400 ft-c of light and a 14-hr photoperiod required approximately 900 degree-days over a 49 F threshold to reach flower-bud stage.

Stands of Russian knapweed (Centaurea repens L.) were reduced over 80 per cent by several combinations of crops, cultivation and herbicides. Two of the best crop rotations in a 4-year trial were: (1) a short season of intensive cultivation and a mid-August seeding of bromegrass that was sprayed with 1 lb/A of butoxyethanol ester of 2,4-dichlorophenoxyacetic acid (2,4-D) during June and 1 or 1½ lb/A during August of the second and third years. (2) Bromegrass seeded with an oat companion crop sprayed with ⅓ lb/A of 2,4-D ester the first year and annual applications of 2,4-D in June and mid-August during the second and third years. The best use of non-selective herbicides in two 2-year trials was spring application of 4 lb/A of diethylamine salt of 2,3,6-trichlorobenzoic acid (2,3,6-TBA) or 6 lb/A of diethylamine salt of polychlorobenzoic acid (PBA), plowing 10 days later, and a corn crop sprayed with ⅓ lb/A of 2,4-D ester followed by a spring-seeded oat crop sprayed with d13 lb/A of 2,4-D ester and postharvest application of 4 to 6 lb/A of 2,3,6-TBA and 6 to 8 lb/A of PBA, and plowing 10 days later. Reinfestation from established plants was not prevented, but annual application of 2,4-D prevented reinfestation from seedlings.

A quick-coupling sprayer tank, a pressure introduction and release valve, and a device for measuring the time elapsed during a spraying run are described.