- Author: Rachael Freeman Long
There have been several alfalfa fields in the Northern Sacramento Valley area that have been deficient in molybdenum (Mo or moly), which is unusual, but not unheard of for the Sacramento Valley. Symptoms of molybdenum deficiency are like those of nitrogen and sulfur deficiency: light green or yellow, stunted plants, caused by a lack of moly that is essential for nitrogen fixation by the rhizobium bacteria that live on alfalfa roots. There may be a region just south of Sacramento that may have alfalfa with somewhat low concentrations of Mo but as you go further south, Mo toxicity begins. Some low copper—high molybdenum soils have been documented in the Modesto and south areas.
Plant tissue testing is the only way to confirm...
- Author: Larry Godfrey
Spring is the optimal time for aphids to flourish. The cool weather is perfect for many aphid species to build-up high numbers. Some aphid species prefer hot conditions but as a general rule cool weather and aphids go “hand-in-hand”. Cole crops, roses, other ornamentals, etc. are stressed by aphids in the spring. Four species of aphids infest alfalfa with the pea aphid and blue alfalfa aphid being favored by the cooler conditions. The spotted alfalfa aphid prefers hot weather and the fourth species, the cowpea aphid, appears to also like hot conditions but populations have also been found at other times of the year.
How do you tell these species apart? A pictorial key is...
- Author: Shannon C. Mueller
We are approaching our sixth month of alfalfa & forage blog postings and it would be great to receive some feedback. Are you enjoying the blog? Is the information helpful? Do you have suggestions for topics you'd like to see or improvements we could make to increase the effectiveness of this blog? Let us know!
- Author: Michelle Leinfelder-Miles
The Sacramento-San Joaquin River Delta region – for its soil type, climate, and irrigation and groundwater sources – is a unique agricultural region of California. Diverse crops are grown in the Delta region, but alfalfa is a particularly important one as the second most widely grown crop. Border check flood irrigation using surface water is the primary method of irrigating Delta alfalfa.
As a forage crop, the marketed product of alfalfa is the vegetation, or alfalfa hay. Hay yields are directly related to crop evapotranspiration (ET), or the water transpired by the crop plus the water evaporated from the soil. As crop ET increases, so does alfalfa yield; although, agronomic and economic reasons put constraints on...
- Author: Carol A Frate
Walking through an alfalfa field the other day, I saw numerous leaves infected with downy mildew. Because only young leaves are susceptible, symptoms are near the top of the plant and easily visible. Early stage symptoms include a light green blotchy area on the leaf surface (Photo 1). In time the area will turn yellow and eventually may dry out (Photo 2). These diseased areas on leaves are usually localized. In the morning when humidity is high, on the underside of the leaf you can see light gray or violet “fuzz” (Photo 3). Look at the “fuzz” with a hand lens. It is the mycelium and spores of the fungal pathogen Peronospora trifoliorum, the cause of downy mildew in alfalfa. The main...