Continuing on with my perusal of the relation of fertility and plant disease out of the excellent “Mineral Nutrition and Plant Disease” by looking at potassium (K) this week. For the record, while I do a lot of reading in this area lately, don't get the impression that this is all I read about! For example I recently finished reading “The Iliad” written by the poet Homer (not in the original Greek though).
There is actually not that much to say about the relationship of potassium and plant disease. The only thing that came out of this chapter that could be relevant to us berry people is that K fertilization has been shown to reduce the severity of vascular wilts in several crop plants caused by Verticillium, but only in situations when it is deficient in the soil. When K is sufficient (something around 200 ppm K and above) in the soil, the disease mitigation benefit of potassium additions is not realized. Too, the effectiveness of the K additions is going to depend on the host plant resistance to the disease, as well as the amount of disease inoculum in the soil.
Bottom line is I'm not seeing a lot for us here. Most of our soils on the Central Coast are close to 200 ppm K or well above (see the link to an excellent survey in the Salinas Valley below), so a benefit in the way of vascular disease resistance through the use of more potassium fertilizer doesn't seem to hold a lot of promise.
Here's one that I've never seen before. True spiders with webbing so heavy that it could interfere with the growing point of raspberry.
On approaching the field, once notices a lot of the very top of many raspberry plants in this field under tunnels with those leaves rolled up. Of course this sets off alarm bells that it could be LBAM, but closer inspection reveals a far heavier webbing than is customary for a leafroller. And... lots and lots of spiders.
What would the call be to do about this? Hard to say, readers if you have experience and/or suggestions what to do, write in and I'll post your answer.
Pics taken today of the situation posted below.
Yellow rust on raspberry has been a common issue of concern for growers and PCA's this past week, very likely this has been spurred on by the wet weather of this past winter.
Recommendations for management available at the UC IPM guidelines
The pictures below are of what some of this rust manifests itself as. Viewing the leaf from the top, one sees an array of darker spots over a lighter background of the chlorotic leaf (not diagnostic, nor do I make any pretensions that this is being caused by the rust disease). Turning the leaf over, one can see the masses of pustules growing at these very spots.
UCCE Farm Advisor Mark Bolda will be providing a training on light brown apple moth (LBAM) that qualifies attendees to be an “approved scout” relating to the Compliance Agreement for shipment of berries to Canada. On completion of the brief training, attendees will receive a Certificate as a record of their participation.
This training will be held once in English and once in Spanish.
Where: UCCE Auditorium, 1430 Freedom Boulevard, Suite E, Watsonville, CA
When: May 10 – 8:00-9:00 AM in English
May 11 – 8:00-9:00 AM in Spanish
No pre-registration necessary. All are welcome to attend, even if they do not intend to ship berries to Canada.
No continuing education hours will be offered at this meeting.
Please call Mark at (831) 763 8025 if you have any questions.
Colleague Mark Gaskell has put together a CE caneberry extension event this coming April 13 that will overshadow any caneberry meeting we have ever planned before.
An A list of researchers from the sectors public and private from around the country will present on :
Caneberry market overview
Caneberry disease and insect management
Nutrient status of primocane blackberries
Evolution of the caneberry industry on the Central Coast
Blackberry production in Mexico
Three new raspberry varieties promising to shake up industry
Caneberry irrigation and nutrient uptake
I will certainly be there - if you want to be up to date on caneberries in California you probably want to find time to be there too.
Meeting will be held at the San Luis Obispo Veterans Memorial Hall, San Luis Obispo and will go from 730 am to 115 pm on April 13.
For more information and registration, see agenda posted here: