Frank L. Young

Winter wheat competition against jointed goatgrass (Aegilops cylindrica) as influenced by wheat plant height, seeding rate, and seed size

Abstract Jointed goatgrass is a troublesome weed in winter wheat with selective control only possible with a herbicide-resistant crop. Even with herbicide-resistant wheat, cultural control is still an important part of jointed goatgrass management. A study was conducted in 1998 and 2000 to determine whether using larger sized seed of a tall wheat variety at an increased seeding rate would reduce the effect of jointed goatgrass on winter wheat. Wheat seed size, seeding rate, and variety height had no effect on jointed goatgrass plant density. Tall (∼130 cm) wheat reduced mature jointed goatgrass biomass 46 and 16% compared with short (∼100 cm) wheat in years 1 and 2 of the experiment, respectively. Spikelet biomass was also reduced approximately 70 and 30% in the same respective years. One thousand–spikelet weight of jointed goatgrass was reduced 37 and 7% in years 1 and 2, respectively, when grown in competition with taller compared with shorter wheat. Moreover, dockage was 80 and 30% less in years 1 and 2, respectively, when grown in competition with taller than shorter wheat. Mature jointed goatgrass height was similar regardless of the competitive wheat height. However, jointed goatgrass was as much as 18% taller than the short wheat and 15% shorter than the tall wheat. Seeding rate had the most consistent effect on wheat yield. Wheat seed yield was about 10% greater with 60 than 40 seed m−1 of row when competing with jointed goatgrass. Results of this study indicate that growers could use a tall winter wheat variety to improve crop competition against jointed goatgrass. Results also indicate that plant breeders should consider plant height because herbicide-resistant varieties are developed for the integrated management of jointed goatgrass. Nomenclature: Jointed goatgrass, Aegilops cylindrica Host. AEGCY; winter wheat, Triticum aestivum L. ‘Nugaines’.

Integration of Weed Management and Tillage Practices in Spring Dry Pea Production

Abstract Spring barley can be used to diversify and intensify winter wheat-based production systems in the U.S. Pacific Northwest. The objective of this study was to describe the effects of tillage system and weed management level (WML) on weed control and spring barley grain yield when grown in a winter wheat-spring barley-spring dry pea rotation. A long-term integrated pest management field study examined the effects of three WMLs (minimum, moderate, and maximum) and two tillage systems (conservation and conventional) on weed control and barley grain yield. Total weed biomass at harvest was 8.0 and 59.7 g m−2 for the maximum and minimum WMLs, respectively, in the conservation tillage system, but was similar and averaged 12.2 g m−2 for all three WMLs in the conventional tillage system. Despite greater weed biomass with minimum weed management in the conservation tillage system, barley grain yields averaged 5,060 and 4,780 kg ha−1 for the conservation tillage and conventional tillage systems, respectively. The benefits of conservation tillage require adequate herbicide inputs. Nomenclature: Barley, Hordeum vulgare L.; dry pea, Pisum sativum L.; winter wheat, Triticum aestivum L. Resumen La cebada de primavera puede ser usada para diversificar e intensificar los sistemas de producción basados en trigo en el Pacífico Noroeste de los Estados Unidos. El objetivo de este estudio fue describir los efectos de los sistemas de labranza y el nivel de manejo de malezas (WML) sobre el control de malezas y el rendimiento de grano de cebada de primavera cuando se produjo en una rotación de trigo de invierno-cebada de primavera-guisante de primavera. Un experimento de campo de manejo integrado de plagas de largo plazo examinó los efectos de tres WMLs (mínimo, moderado, y máximo) en dos sistemas de labranza (conservación y convencional) sobre el control de malezas y el rendimiento de grano de la cebada. La biomasa total de malezas al momento de la cosecha fue 8.0 y 59.7 g m−2 para el WMLS máximo y mínimo, respectivamente, en el sistema de labranza de conservación, pero fue similar y promedió 12.2 g m−2 para todos los tres WMLs, en el sistema de labranza convencional. A pesar de que hubo una mayor biomasa de malezas con el manejo mínimo de malezas en el sistema de labranza de conservación, los rendimientos de grano de la cebada promediaron 5,060 y 4,780 kg ha−1 para los sistemas de labranza de conservación y convencional, respectivamente. Los beneficios de la labranza de conservación requieren insumos adecuados de herbicidas.

Control of Volunteer Herbicide-Resistant Wheat and Canola

Volunteer crops resistant to glyphosate and other herbicides pose a potential problem for Pacific Northwest (PNW) growers that rely on glyphosate for control of volunteer crops and weeds during fallow and before planting. Herbicides for control of volunteer herbicide-resistant wheat and canola in PNW conservation tillage systems were evaluated during 2000 and 2001 near Ralston, WA, and Moscow, ID. Paraquat + diuron controlled glyphosate- and imidazolinone-resistant wheat ≥90%, and glyphosate controlled imidazolinone-resistant wheat 88 to 96% 14 d after treatment (DAT). Glyphosate- and imidazolinone-resistant wheat were controlled only 58 to 85% with quizalofop-P and clethodim 14 DAT. By 21 DAT, imidazolinone-resistant wheat control with clethodim and quizalofop-P was ≥93%, but the longer time period required for control to reach an acceptable level could increase disease and insect problems associated with volunteer wheat. Volunteer glyphosate-resistant canola was controlled 92 and 97% 14 DAT and 76 and 98% 21 DAT with paraquat and paraquat + diuron, respectively. Treatments that contained glyphosate controlled imidazolinone- and glufosinate-resistant canola >84% 14 DAT. By 21 DAT, control of imidazolinone- and glufosinate-resistant canola was 94 to 98% with paraquat + diuron and all glyphosate treatments, except glyphosate–isopropylamine salt (IPA) + glufosinate (88 to 93%) and glyphosate-IPA + paraquat (67 to 85%). In these studies, paraquat + diuron was the best alternative to glyphosate for controlling volunteer herbicide-resistant wheat and canola. Nomenclature: Clethodim; diuron; glufosinate; glyphosate; imidazolinone; paraquat; quizalofop-P; canola, Brassica napus L. ‘DKL 27-20’, ‘Phoenix’, ‘Pioneer 45A71’; wheat, Triticum aestivum L. ‘Bobwhite’, ‘FS-4 IR’. Additional index words: Direct seeding, glufosinate resistant, glyphosate resistant, green-bridge, imidazolinone resistant. Abbreviations: ACCase, acetyl coenzyme A carboxylase; DA, diammonium salt; DAT, days after treatment; HRC, herbicide-resistant crops; IPA, isopropylamine salt; PNW, Pacific Northwest.

Vernalization response of plants grown from spikelets of spring and fall cohorts of jointed goatgrass

Abstract Jointed goatgrass is most commonly described as a winter annual species. However, it has been observed to produce spikes in spring crops, apparently without being exposed to vernalizing conditions. A controlled environment study was conducted to determine the reproductive response of jointed goatgrass plants grown from seeds of fall- and spring-emerging parent plants to various vernalization durations. Winter wheat was included as a control. Winter wheat spikelet production was dependent on vernalization, and the number of spikes per plant was 10-fold greater if the plants were exposed to 4 C for 10 wk. In contrast, jointed goatgrass spike production without vernalization remained as high as 50% of that produced by plants exposed to 10 wk of vernalization conditions. Jointed goatgrass is thus not as dependent on vernalization for reproduction as the comparative winter wheat standard. Apparently, jointed goatgrass is more a facultative rather than an obligate winter annual. Rotating to a spring-seeded crop should not be expected to completely prevent jointed goatgrass seed production. Fields rotated to spring wheat to eliminate jointed goatgrass seed production should be monitored, and jointed goatgrass should be hand pulled or otherwise controlled to ensure zero seed production. Nomenclature: Jointed goatgrass, Aegilops cylindrica L. AEGCY; winter wheat, Triticum aestivum L. ‘Madsen’.

Cereal Aphid and Natural Enemy Populations in Cereal Production Systems in Eastern Washington

Abstract A 5 yr study in the semiarid wheat production region of eastern Washington documented the relative densities of pest aphids and their natural enemies in cereal production systems using on-farm replicated plots. The systems were reduced-tillage soft white winter wheat (SWW) (Triticum aestivum L.)—summer fallow rotation; no-till soft white spring wheat (SWS)—chemical fallow rotation; continuous no-till hard red spring wheat (HRS); and no-till HRS—no-till spring barley (SB) (Hordeum vulgare L.) rotation. The English grain aphid, Sitobion avenae (F.), was the dominant species, followed in abundance by the Russian wheat aphid, Diuraphis noxia (Mordvilko). The bird cherry-oat aphid, Rhopalosiphum padi (L.), and rose grass aphid, Metopolophium dirhodum (Walter), were infrequently encountered. Overall, aphid densities were low, with aphids rare or absent in SWW and SB plots. The data revealed no clear and consistent effects of cereal production systems on aphid densities, but it did reveal, based on analysis of data from continuous HRS plots, high among-year variability in S. avenae and D. noxia densities. Only in 1996 and only in continuous HRS was it necessary to chemically control damaging populations of D. noxia. English grain aphid densities never approached threshold levels. S. avenae parasitism averaged >16% in some spring wheat systems in 1998 and 2000, while only two mummified D. noxia were observed. Coccinellid beetle counts in all plots totaled 143 in 1998 and 163 in 2000, with 90.2% and 94.5% in the genus Hippodamia, respectively. The ladybird beetle Coccinella septempunctata L. comprised 9.8% (1998) and 5.5% (2000) of the populations. The results suggest that damaging aphid populations are unlikely to develop in winter wheat, but populations in spring cereals warrant monitoring because they fluctuate from year-to-year and can be damaging.

Monitoring Russian Thistle (Salsola iberica) Root Growth Using a Scanner-Based, Portable Mesorhizotron1

A mesorhizotron and scanning system was modified to study the development of Russian thistle root systems during the 1996 and 1997 growing seasons at Lind, WA. Our imaging equipment combined the full profile images afforded by conventional rhizotrons with the portability of cylinder-based minirhizotron systems at a fraction of the cost of either system. Root development of Russian thistle in early spring was rapid and extensive compared with shoot growth. In 1996, 30 d after planting (DAP) Russian thistle roots were at least five times as long as the corresponding plants shoots. During the next 20 d, shoots grew a maximum of 20 cm, whereas roots grew a maximum of 120-cm deep. Maximum root elongation rate reached 2 to 3 mm/cm2/d at the 70- to 120-cm depths 30 to 50 DAP in 1996 and 55 to 70 DAP in 1997. More than one (multiaxial grouping) Russian thistle root was often observed growing through the same soil channels. After the rapid early season growth, roots began to shrink or die back until shoots were clipped to simulate wheat harvest. Within 7 d after harvest, roots regenerated in old root channels. Our mesorhizotron system is a promising inexpensive tool for monitoring root morphological development of Russian thistle under field conditions. Nomenclature: Russian thistle, Salsola iberica Sennen and Pau #3 SASKR; wheat, Triticum aestivum L. Additional index words: Root development in situ. Abbreviations: DAP, days after planting; RER, root elongation rates.

Spring-germinating jointed goatgrass (Aegilops cylindrica) produces viable spikelets in spring-seeded wheat

Abstract The most common strategy recommended for management of jointed goatgrass infestations is to rotate from winter wheat to a spring crop for several years. A field study was conducted at three locations in 1998 and 1999 to determine the effects of spring seeding date on the ability of jointed goatgrass to flower and produce viable seed in the presence or absence of spring wheat and to determine the effect of jointed goatgrass competition and crop seeding date on spring wheat grain yield. Spring wheat was seeded on four dates at each location in both hand-sown and natural jointed goatgrass infestations. Jointed goatgrass plants from hand-sown spikelets flowered and developed spikelets on all seeding dates except the last; viable seed was produced on the two earliest seeding dates. Jointed goatgrass plant densities from natural infestations were from 1 to 12 plants m−2, and spikelet production ranged from 0 to 480 spikelets m−2. Natural jointed goatgrass infestations produced spikelets containing viable seed on all seeding dates at one location in 1998, the driest location. Spring wheat yield was not affected by jointed goatgrass competition; however, jointed goatgrass spikelet production was reduced by spring wheat competition compared with that of monoculture jointed goatgrass. The last seeding date of spring wheat was associated with 51% less crop yield compared with the recommended seeding date. The decision to manage jointed goatgrass infestations with a spring crop rotation should consider delayed seeding dates to minimize viable spikelet production by spring-germinating jointed goatgrass; however, the cost of this decision may include grain yield reduction. Nomenclature: Jointed goatgrass, Aegilops cylindrica Host. AEGCY; spring wheat, Triticum aestivum L. ‘Penewawa’.

Canola integration into semi-arid wheat cropping systems of the inland Pacific Northwestern USA

Abstract. The inland Pacific Northwestern USA (iPNW) wheat-producing region has a diversity of environments and soils, yet it lacks crop diversity and is one of the few semi-arid wheat-growing regions without significant integration of oilseeds. Four major agroecological zones, primarily characterised by water availability, feature distinctly different fallowed and annually cropped systems, each presenting different challenges and opportunities to integrate winter and spring canola. Although major interests in regional energy crops and rotational diversification spurred feasibility research on iPNW canola food, feed and fuel production in the 1970s, commercial canola adaptation has lagged behind other semi-arid wheat regions for various socioeconomic, ecophysiological and agronomic reasons. New federal crop insurance policies will reduce economic risks in new crop adaptation, and oilseed processing facilities are creating new local markets. Although canola management largely relies on wheat farm equipment, agronomic approaches require strategic adjustments to account for physiological differences between canola and cereals including seed size, seedling morphology and responses to temperature extremes. Climate change predictions for the region threaten to exacerbate current hot and dry summers and research aims to develop and adapt flexible winter and spring canola-based systems to regional water and temperature stressors in each zone. Adaptation will require novel planting, fertilisation and weed control strategies to successfully establish improved winter canola cultivars in hot dry summers that survive cold winters, and spring canola cultivars direct-seeded in cool wet springs. The adaptation of winter and spring canola will somewhat mirror the rotational placement of winter and spring cereals within each zone. Economic analysis of oilseed break crop benefits such as weed and disease control will help to demonstrate the medium-term economic benefits of crop diversification to support the growth of a regional canola industry in the iPNW.

Integrated Weed Management Systems Identified for Jointed Goatgrass (Aegilops cylindrica) in the Pacific Northwest

Abstract Jointed goatgrass is an invasive winter annual grass weed that is a particular problem in the low to intermediate rainfall zones of the Pacific Northwest (PNW). For the most part, single-component research has been the focus of previous jointed goatgrass studies. In 1996, an integrated cropping systems study for the management of jointed goatgrass was initiated in Washington, Idaho, and Oregon in the traditional winter wheat (WW)–fallow (F) region of the PNW. The study evaluated eight integrated weed management (IWM) systems that included combinations of either a one-time stubble burn (B) or a no-burn (NB) treatment, a rotation of either WW–F–WW or spring wheat (SW)–F–WW, and either a standard (S) or an integrated (I) practice of planting winter wheat. This study is the first, to our knowledge, to evaluate and identify complete IWM systems for jointed goatgrass control in winter wheat. At the Idaho location, in a very low weed density, no IWM system was identified that consistently had the highest yield, reduced grain dockage, and reduced weed densities. However, successful IWM systems for jointed goatgrass management were identified as weed populations increased. At the Washington location, in a moderate population of jointed goatgrass, the best IWM system based on the above responses was the B:SW–F–WW:S system. At the Washington site, this system was better than the integrated planting system because the competitive winter wheat variety did not perform well in drought conditions during the second year of winter wheat. At the Oregon site, a location with a high weed density, the system B:SW–F–WW:I produced consistently higher grain yields, reduced grain dockage, and reduced jointed goatgrass densities. These integrated systems, if adopted by PNW growers in the wheat–fallow area, would increase farm profits by decreasing dockage, decreasing farm inputs, and reducing herbicide resistance in jointed goatgrass. Nomenclature: Jointed goatgrass, Aegilops cylindrica Host AEGCY; wheat, Triticum aestivum L. ‘Madsen’, ‘Stephens’, ‘Penawawa’, ‘Rod’, ‘Eltan’, ‘Alpowa’.

Influence of long-term tillage and crop rotations on soil hydraulic properties in the US Pacific Northwest

In the low precipitation zone (<0.3 m [11.8 in] annual precipitation) of the Inland Pacific Northwest, no-tillage continuous spring cereal and no-tillage spring cereal-chemical fallow rotations are being examined as alternatives to the traditional winter wheat–summer fallow rotation for soil conservation. There is limited information, however, regarding the long-term effects of no-tillage cropping systems on soil hydraulic properties in this semiarid region. The objective of this study was therefore to characterize infiltration, water retention, saturated hydraulic conductivity and bulk density of a silt loam that had been subject to various tillage and crop rotations in east-central Washington. Treatments examined included no-tillage spring barley–spring wheat (NTSB–SW), no-tillage spring wheat–chemical fallow (NTSW–ChF), and traditional winter wheat–summer fallow (WW–SF). Soil properties were measured in spring and late summer 2006 due to the vulnerability of the soil to rapidly dry and erode during these seasons. Saturated hydraulic conductivity was determined by the falling-head method, infiltration was measured using a double-ring infiltrometer, and water retention characteristics was assessed by examining the temporal variation of in situ soil water content. NTSB–SW resulted in higher infiltration and saturated hydraulic conductivity, lower bulk density, and larger and/or more continuous pores in the upper soil profile (<0.1 m [<3.9 in] depth) than WW–SF and NTSW–ChF. Infiltration and saturated hydraulic conductivity were lower for chemical fallow than for traditional fallow in spring whereas hydraulic conductivity was lower for summer fallow than chemical fallow in late summer. Soil hydrologic properties appeared more favorable for no-tillage continuous spring cereal rotations. These results are useful for soil and water management and conservation planning in the low precipitation zone of the Inland Pacific Northwest.