Field observations in 1986 indicated that increased injury to soybean could occur from clomazone plus metribuzin and clomazone plus linuron compared with metribuzin or linuron alone. Field experiments to measure this response were conducted in 1988, 1989, and 1990 at two locations in Michigan. Atrazine at 0, 1120, 2240, and 3360 g ha-1was applied the year previous to soybean planting to determine if atrazine residues in the soil influenced soybean response. Herbicide treatments in soybean included clomazone, metribuzin, linuron, alachlor, clomazone plus metribuzin or linuron, alachlor plus metribuzin or linuron, and an untreated control. Additive and synergistic responses in soybean to clomazone plus linuron and clomazone plus metribuzin, regardless of atrazine application rate, occurred in some field environments. Experiments in the greenhouse demonstrated that soybean shoot weight was reduced synergistically from clomazone plus metribuzin compared with either herbicide alone, and the response was greater on a soil with 2.5% organic matter compared with a soil with 4.4% organic matter. Clomazone plus metribuzin reduced leaf area and shoot dry weight, regardless of placement, while leaf area and shoot dry weight were reduced more when clomazone plus linuron- and atrazine plus metribuzin-treated soil was placed in the same zone as the soybean seed. The synergistic interaction in soybean to clomazone plus metribuzin occurred under both cool and warm temperature regimes in growth chamber studies.

Field research was conducted in 1985 and 1986 to compare the efficacy of fluazifop and quizalofop on production of panicles and seeds of red rice. Single and first sequential treatments were applied to red rice in the early-tillering, midtillering, and panicle initiation stages of growth. Sequential treatments were applied 14 days after each earlier application to red rice in the midtillering, late-tillering, and early-heading growth stages, respectively. Both herbicides were applied singly or sequentially at 70, 140, and 280 g/ha. Sequential applications of fluazifop and quizalofop at 280 g/ha caused the greatest reduction of red rice panicle and seed production. Fluazifop at 280 g/ha applied sequentially reduced panicle production 75 to 80% and seed production 80%; 140 g/ha applied sequentially reduced seed production 83%. Quizalofop at 280 g/ha applied sequentially reduced panicle production 75 to 100% and seed production 91%. Sequential applications of either herbicide applied to red rice plants in the panicle initiation and early-heading growth stages were the most effective treatments.

Experiments were conducted in 1985 and 1986 at three locations in eastern Arkansas to evaluate red rice control in soybeans with postemergence grass herbicides and plant growth regulators applied singly or sequentially at early to late-tillering growth stages of red rice. Haloxyfop at 0.21 kg ai/ha and quizalofop at 0.14 kg ai/ha applied singly or sequentially and fluazifop at 0.21 kg ai/ha applied sequentially consistently controlled red rice and suppressed seedhead production in soybeans. Mid-season treatments were not beneficial when high soil moisture stress conditions existed. Mefluidide or sethoxydim applied singly or sequentially or amidochlor applied singly provided erratic control and seedhead suppression of red rice in soybeans.

Research was conducted in soybean and common cocklebur to determine if the synergistic interactions of clomazone plus metribuzin and clomazone plus linuron were due to the effect of one herbicide on root uptake, partitioning, or metabolism of the other. Treatments consisted of14C-clomazone alone and combined with metribuzin or linuron,14C-metribuzin alone and combined with clomazone, and14C-linuron alone and combined with clomazone. Root uptake and partitioning of clomazone applied alone in soybean differed compared to clomazone plus metribuzin. Root uptake and partitioning of metribuzin or linuron did not differ when applied alone or combined with clomazone. Binding of clomazone or its metabolites in an unextractable form may be a method of deactivating clomazone by soybean, but not by common cocklebur. Levels of parent clomazone were higher in common cocklebur roots when clomazone was combined with metribuzin and linuron compared to clomazone done. Levels of parent metribuzin were higher in soybean roots, and in common cocklebur roots and shoots when clomazone was combined with metribuzin compared to metribuzin alone. Levels of parent linuron were greater in soybean shoots when linuron was applied with clomazone compared to linuron alone. These results indicate that the metabolism of metribuzin and linuron is altered in both species when clomazone is applied, leading to increased phytotoxicity.

The Interregional Research Project Number 4 (IR-4) Specialty Food Crops Program is a publicly-funded program initiated in 1963 to develop and submit regulatory data to support registration of pest control products for specialty crops. In the early to mid 1990s, nearly 45% of the IR-4 residue projects supported new herbicide registrations for fruits and vegetables with the other 55% devoted to fungicides, insecticides, and nematacides. In 2005, the number of residue projects conducted by IR-4 to support herbicide fruit and vegetable registrations was less than 30%. The three main factors that have contributed to this decline are: fewer herbicides available for registration; product liability concerns; and an increased focus on new, safer, and Reduced Risk Pesticides for insect and disease control. It has been a number of years since a new herbicide has been developed for a major crop that could be extended to specialty food crops. Many of the current IR-4 herbicide projects are with products that have been on the market for 20 or more years. Product liability is a concern because of the high value of many specialty crops relative to the potential market opportunity. In many cases, the registrant requires product performance data before IR-4 can proceed with a residue project. With limited funds for developing these data, many new projects never proceed to the regulatory stage. Although registrants can seek indemnification for some of these uses, it is a complicated often state-specific process. IR-4 has been successful in a number of areas, including the registration of a large numbers of uses through reduced data extrapolations for products such as glyphosate and carfentrazone-ethyl. Additionally, IR-4 submitted the first successful petition establishing an exemption of tolerance for a conventional herbicide (imazamox). Future IR-4 initiatives include collaboration with industry, growers, and academia to develop new herbicide technologies such as plant breeding or transgenic crops and generation of appropriate data to extend those products to specialty food crops. IR-4 will also assist in registering products that can be used on crops that have been selected (or developed through biotechnological approaches) to be tolerant to existing herbicides. Registrants should strongly consider developing herbicides for specialty food crops, with IR-4's assistance, as a means to expand markets and also as a means to extend data protection of their products, as allowed under the Food Quality Protection Act.