A friend sent me these photos from an alfalfa field near the Merced area in California's Central Valley.  Can you diagnose what this is?

We're not 100% sure what it is, but have a pretty good idea- and have provided a view at the end of this blog - but see if you can diagnose this yourself.

Here are a few hints:

• Symptoms appeared several weeks ago, in February/March, 2014
• This field had been irrigated twice during winter time due to the drought this year, followed by late Feb early March rains
• These are quite heavy clay-loam soils
• The pH of the soil is rather high, probably 7.5 to 8.2
• Symptoms were generally widespread...

Blue alfalfa aphid (BAA) populations have again been seen in southern and central California including locations in the Imperial, Palo Verde, Antelope, and San Joaquin Valleys (see Peter Goodell blog from 16 January 2014). In many locations, this was even an earlier build-up than observed in 2013. There are many theories and rumors as to what is causing this BAA population build-up. The “bottom-line” is that we do not know conclusively and research needs to be done to determine the reasons for this. The goal is to put together the resources (funding and personnel) to study this situation in a reasonable period of time. In the short-term, management practices will need to be developed to get through this situation until more...

The recent rains were a welcome relief for many parts of our state, but we are still in a serious drought with our reservoirs and snowpack at historical low levels. Ensuring adequate water for crops will be a challenge this year.

In general, perennial crops, such as orchards and vineyards, cannot survive extended periods without irrigation. However, alfalfa is more resilient because it can go into a drought-induced dormancy over the summertime, at least for one year. The tradeoff is that without water there will be little yield, but research has shown that the stand will persist on most soil types and yield will recover the next year once water is applied to the field again.    

In most years hay growers...

For those of you who have followed the controversy about the export of ‘virtual water' in the form of hay exported to other countries – there is a recent article posted in January on the National Geographic Website: “Exporting the Colorado River to Asia, through hay”

Photo: Water conveyed from the Colorado River to the Imperial Valley.  Alfalfa hay as well as a plethora of winter vegetables in rotation with alfalfa are grown there.  (Mark Henle, National Geographic, photo)

This article follows up on Robert Glennon's October 2012 piece in the...