Inhibition of Orobanche crenata Seed Germination and Radicle Growth by Allelochemicals Identified in Cereals

Orobanche crenata is a parasitic weed that causes severe yield losses in important grain and forage legume crops. Cereals have been reported to inhibit O. crenata parasitism when grown intercropped with susceptible legumes, but the responsible metabolites have not been identified. A number of metabolites have been reported in cereals that have allelopathic properties against weeds, pests, and pathogens. We tested the effect of several allelochemicals identified in cereals on O. crenata seed germination and radicle development. We found that 2-benzoxazolinone, its derivative 6-chloroacetyl-2-benzoxazolinone, and scopoletin significantly inhibited O. crenata seed germination. Benzoxazolinones, l-tryptophan, and coumalic acid caused the stronger inhibition of radicle growth. Also, other metabolites reduced radicle length, this inhibition being dose-dependent. Only scopoletin caused cell necrotic-like darkening in the young radicles. Prospects for their application to parasitic weed management are discussed. © 2013 American Chemical Society.This research is supported by projects FP7-ARIMNet-MEDILEG and AGL2011-22524 (cofinanced by FEDER funds).Peer Reviewe

Crop Profile for Barley in Washington

Washington State ranked fourth in U.S. Barley production in 1999 with 10.3% of the U.S. crop. Eastern Washington counties produce this nonirrigated grain crop. Growing conditions, culture and common pest problems are discussed and illustrated in color. Control measures are given where applicable. 20 pages

Integrated management of jointed goatgrass in the Pacific Northwest

Jointed goatgrass is a weed that competes with wheat, resulting in reduced yield and increased grain dockage. Managing jointed goatgrass in winter wheat requires a systems approach that integrates multiple control tactics, described in this bulletin. Although jointed goatgrass is a major problem in most winter wheat growing areas west of the Mississippi River, the climate and cropping patterns of the Pacific Northwest (PNW) are unique and may influence the choice of options available for effective management of this pest. In particular, producers have noted that by adopting direct seed/reduced tillage management systems, both the number of jointed goatgrass infestations and the densities of these infestations tend to increase

Amostragem do banco de semente e flora emergente de plantas daninhas Sampling of weed seedbank and emerged populations

O objetivo desta pesquisa foi determinar o número de amostras necessárias para estimar com precisão aceitável a quantidade de sementes no solo e a flora de plantas daninhas emergentes, em áreas experimentais e de lavoura, para auxiliar na tomada de decisão das estratégias de manejo das plantas daninhas. A amostragem do solo para quantificação do banco de sementes foi feita com trado tubular de 5,0 cm de diâmetro, na profundidade de 0 a 10 cm. A flora emergente foi contada por meio de um gabarito de ferro nas dimensões de 0,5x0,5 m, de forma aleatória na área. O número de amostras necessário foi estimado em razão da média de sementes da amostra, para uma determinada precisão (CV = 20% ou 40%). Foi estimado que, nas áreas experimentais, para médias de 10 a 20 sementes/amostra de solo (500 a 1.000 sementes/m²) e coeficiente de variação de 20%, são necessárias entre 40 e 90 amostras, respectivamente; com 40% (menor precisão), entre 10 e 20 amostras. Considerando o mesmo intervalo em áreas de lavoura, representativas de glebas homogêneas, o tamanho de amostragem necessária é cerca de três vezes maior. Levantamentos da flora daninha emergente apresentam menor associação dos dados (média e variância) entre si, portanto, são menos apropriados para decisões de manejo.<br>The objective of this research was to determine the number of soil samples needed to estimate with reasonable precision level the amount of seeds in the soil and the emerged weeds, in a seedbank of experimental and cropland areas, in order to help management decisions. Sampling the soil seedbank was carried out by using a tubular soil sampler core of 5 cm diameter, from 0 to 10 cm soil depth. Emerged weeds were scouted by placing iron quadrats (0.5x0.5 m), randomly. The number of samples required was estimated as a function of the average seeds per sample, given a required precision (CV = 20% or 40%). For the small plots, means between 10 and 20 seeds/soil sample (500 to 1,000 seeds/m²) and CV of 20%, it would be necessary 40 to 90 samples, respectively; with CV of 40% (lower precision), the need would be 10 to 20 samples. For the same seed number per soil sample in cropland areas, estimated sample size is about tree times higher. Emerged weed scouting presents lower data correlation between mean and variance, and was less appropriated for handling weed management decisions