This chapter examines the importance of pest management in crop production and details the commercially available biotechnology‐derived traits and the need for them in the context of available pest management options in conventional crops. The discussion is mainly focused on the actual and potential benefits of this innovation for crops commercialised so far in the United States. Economic advantage to growers is the ultimate key factor, which determines the adoption and success of biotechnology‐derived crops. Economic benefits normally result from reduced input costs, or increased yields or both.

Research in irrigated and nonirrigated corn production systems was conducted to evaluate the effect of leaf architecture of corn hybrids on weed management. The corn hybrids used in each study were ‘Pioneer 3394’ (upright leaf) and ‘Pioneer 3260’ (horizontal leaf). In the irrigated study, residual weed control treatments included two rates of prepackaged mixtures of metolachlor plus atrazine, encapsulated acetochlor plus atrazine, nonencapsulated acetochlor plus atrazine, or a tank mixture of simazine and metolachlor plus atrazine. In the irrigated experiments, horizontal leaf architecture reduced weed density (all three sites in 1 of 2 yr), weed biomass (five of six sites), solar radiation reaching the ground (all six sites), and weed seed production (one site each year) compared with upright leaf architecture. Weed density and weed biomass did not differ between herbicide rates or acetochlor formulation at any site. Corn hybrid was significant for yield at only one site. Reduced weed biomass did not translate into yield differences. The nonirrigated study evaluated two factors at four sites over 2 yr: leaf architecture (upright or horizontal leaf) and weed management program (preemergence residual and postemergence no residual) at two application rates. Neither weed density nor weed biomass was reduced because of corn leaf architecture or herbicide rates in the nonirrigated study. No interaction was detected in either irrigated or nonirrigated studies between leaf architecture and herbicide treatments, indicating that these factors are independent of one another. On the basis of these studies, it appears that horizontal leaf architecture of corn hybrids can assist in integrated weed management in irrigated corn production but may not be beneficial when corn is grown under drought-prone conditions.

Glufosinate at 1.1 and 2.2 kg/ha injured ‘Koshihikari’ rice lines that were transformed with the BAR gene from 0 to 53%. However, transgenic ‘Gulfmont’ rice was not injured. Rice yields of transgenic ‘Gulfmont’ lines and six of nine ‘Koshihikari’ lines were not affected by 2.2 kg/ha glufosinate. In field studies, flooding reduced the efficacy of glufosinate in controlling red rice, and greenhouse tests determined that glufosinate efficacy was reduced when red rice was submerged between 25 and 50% of its height. Plant heights and dry weights of red rice increased as flood water depth increased at all rates of glufosinate.

Glufosinate at 2.2 kg ai/ha injured rice transformed with the BAR gene more when applied to one- to two-leaf (23 to 26%) than to three- to four-leaf (13 to 19%) plants. Visible injury was least when applications were made at boot stage (3 to 14%). However, applications at boot stage caused an average grain yield reduction of 16%. Most treatments did not influence rice plant height. Among single applications (0.3, 0.4, 0.6, 0.8, and 1.1 kg/ha), 1.1 kg/ha glufosinate at three- to four-leaf stage of red rice resulted in greater control (91%) than at panicle initiation (74%) or at boot stage (77%). Injury to red rice was two to 11 times greater than the injury to BAR-transformed rice depending on glufosinate rate and application timing.

Glufosinate applied postemergence alone and in mixture with pendimethalin, thiobencarb, quinclorac, propanil, bensulfuron, bentazon, acifluorfen, or triclopyr was evaluated on bialaphosresistant (BAR) rice and red rice in field studies. Glufosinate at 2.2 kg ai/ha alone was less phytotoxic (6%) to BAR-transformed rice than when it was applied in combination with 0.4 kg ai/ha triclopyr (59%) or 0.6 kg ai/ha acifluorfen (22%). Rice yield with glufosinate alone was similar to the weed-free check the first year, but 13% less than the weed-free check the second year. For the glufosinate plus triclopyr mixture, rice yield was reduced by 39 and 76% compared with glufosinate alone in 1994 and 1995, respectively. Red rice control was 92% with either 3.4 kg ai/ha propanil or 0.6 kg/ha acifluorfen mixed with 0.6 kg/ha glufosinate, which was greater than for glufosinate alone and the other combinations. Propanil or acifluorfen mixed with glufosinate reduced red rice plant height, panicle maturity, and 100-seed weight 16, 31, and 24%, respectively, compared to glufosinate alone and 30, 48, and 43%, respectively, compared to the nontreated weedy check.

Reciprocal controlled crosses were made in the greenhouse between Gulfmont rice transformed with the bialaphos resistance (BAR) gene and red rice and BAR-transformed Koshihikari rice and red rice to assess the inheritance of glufosinate resistance. All F1 plants were resistant to 2.2 kg ai/ha glufosinate. Ammonia accumulation as a measure of glufosinate resistance in the F1 hybrids was assayed at 4 and 8 days after treatment (DAT). Ammonia accumulation in hybrids 4 DAT was similar to glufosinate treated, transformed rice, while treated nontransformed plants accumulated 14 to 23 times more ammonia compared with the hybrids. The nature of inheritance of glufosinate resistance in F2 rice plants was studied by a glufosinate dip test, a spray test, and ammonia assay. All three tests confirmed that glufosinate resistance, as influenced by the BAR gene, segregated in a 3 (resistant): 1 (susceptible) ratio.

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A 6-yr project comparing four cash grain–farming systems relevant to the mid-Atlantic region of the United States was conducted from 1993 to 1999. A wide range of parameters was sampled including soil health, nutrient and agrichemical movement, economic viability, and insect and weed communities. The systems and their approaches to weed management were: continuous no-till corn without (System A1) or with (System A2) rye cover crop and preplanned herbicides based on expected weed infestations; System B was a 2-yr corn–soybean rotation with conventionally tilled corn and no-tillage soybean, with preplanned herbicides based on expected weed infestations; System C was a 2-yr rotation with no-till corn, conventionally tilled wheat, and no-till double-cropped soybean, using postemergence (POST) herbicides on the basis of field scouting; and System D was a 3-yr rotation of corn-soybean-winter wheat with rye and hairy vetch cover crops, using cultivation and reduced rates of POST herbicides based on field scouting. Spring weed assessment in 1999 was similar for species evenness (Shannon's E) and diversity (Shannon's H′) indices. Weed density was lowest in System C because wheat in this system received a spring herbicide application. In the final fall assessment, Shannon's H′ was greater in System D than System C. Common lambsquarters, eastern black nightshade, and jimsonweed were more abundant in System D than Systems A1, A2, and C. Fall 1999 assessment also indicated Canada thistle was more prevalent in Systems A1 and A2 than the other three systems. During the 6-yr period, densities of jimsonweed, eastern black nightshade, morningglory species, crabgrass, and fall panicum dramatically increased in a particular system for 1 to 2 yr, then declined to levels similar to other systems. Overall, weed communities were quite stable and effective weed management did not result in dramatic changes in the weed community, regardless of the approach to cropping systems or weed management.