T RIIODOBENZOIC acid (TIBA) has been used to increase floral development of plants. Zimmerman and Hitchcock (9) reported that TIBA, when applied to tomato plants, would cause ordinary vegetative buds to produce flowers. They also noticed that more axillary growth was produced by plants treated with TIBA. Galston (4) studied the effects of TIBA on flowering in soybeans. He reported that vegetative plants were not induced to flower by TIBA, but photoinduced plants showed a tenfold increase in the number or floral buds.

Research was conducted to compare the relative phytotoxicity of trifluralin (a,a,a‐trifluro‐2,6‐,dinitro‐N,N‐dipropyl‐p‐toluidine) with several analogues, and to establish an indices for comparing alternative structural substitutions. GR50 and visual injury values were used to evaluate relative phytotoxicities. There appeared to be a direct correlation between phytotoxicity and selected structural changes on the dinitroaniline ring. The dinitroaniline ring substitutions in order of decreasing phytotoxicity to bioassay indicator plants were substitutions in the one and five positions, one only, and four only. Least phytotoxic was the combined one and four position substitution on the ring.

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Hophornbeam copperleaf (Acalypha ostraefolia Ridd), an increasing weed problem in peanuts (Arachis hypogaea L.) in the southwestern United States, is resistant to most presently used herbicides. Research was conducted to design and evaluate production systems that would provide full season control of this weed in peanuts. Screening experiments indicated several herbicides would control copperleaf but that they were not selective for peanuts. Preliminary systems utilizing alachlor (2‐chloro‐2',6'‐diethyl‐N‐(methoxymethyl)acetanilide) at 2.24 kg/ha combined with rotary cultivation provided early but not full season control. Ultimately systems involving a preplant herbicide, alachlor or fluorodifen (p‐nitrophenyl α,α,α‐trifluoro 2‐nitro‐p‐totyl ether) either preemergence or with several postemergence combinations, and timely cultivations were developed that controlled copperleaf for the entire growing season. Fluorodifen combinations (at 5 kg/ha) applied postemergence to peanuts and copperleaf up to 7.5 cm tall provided excellent weed control with no visible crop injury.

No abstract