Alkaliweed (Cressa truxillensis) is a native perennial plant of the western USA and in California, they are found primarily in saline and alkaline soils. Lately, it has been observed in Central Valley pistachio, olive, and almond orchards as a problematic species. Very little information is available on the effect of environmental factors on germination, shade tolerance, and the response of this species to herbicides. Therefore, studies were conducted to assess the effect of environmental factors (water potential, salinity, and pH) on seed germination, the influence of shade (30% shade 70% shade, and no shade) on aboveground growth, and the response of alkaliweed to common registered post-emergent herbicides. Results showed that the seeds were moderately tolerant to drought but highly adapted to salinity and pH as germination occurred up to an electrical conductivity level of 20 dS m-1 and pH range of 5 to 9. Both shade levels reduced aboveground growth and formation of reproductive structures. None of the postemergence herbicides provided adequate control of the plants. Therefore, an integrated management plan needs to be developed for alkaliweed control in Central Valley orchards.
Keywords: Convolvulaceae; perennial cropping systems; postemergence herbicides; semi-arid environments; weed management.