Accompanying the current spate of Macrophomina and Fusarium discoveries by the UCCE Diagnostic Laboratory in Salinas and by other pathologists, growers, farm managers, and PCAs are now faced with the question of what the next step should be.
Fumigation: The advice for growers and farm managers is to avoid bed fumigation at this juncture. Even beds fumigated by professional operators will have little reservoirs of surviving pathogens on the shoulders where the fumigant did not travel. Of great concern are pathogen populations surviving in the soil making up the untreated furrows. Growers who are not flat fumigating with methyl bromide + chloropicrin should consider using a high rate of chloropicrin under impermeable film. This likely will not be as good a treatment as the mix of methyl bromide + chloropicrin used in the past, but it is the next best soil treatment solution.
Reducing stress to the plants: The diseases caused by both Macrophomina and Fusarium develop earlier, more rapidly, and more severely if plants are stressed. Strawberries that are under-chilled or subject to irrigation deficits, fertility shortfalls, and/or pest issues (such as mites) can succumb fairly rapidly, while those perfectly managed can withstand disease for a longer time. Growers wanting to reduce their diseases losses from here on out will need to play a tight defensive game and address plant stress factors in a timely manner.
Not disturbing the existing bed: The in-field spread of both Macrophomina and Fusarium is mainly accomplished by tillage and other procedures that move soil around. Because neither pathogen makes airborne spores (such as those made by powdery mildew and gray mold pathogens) or swimming zoospores found in soil water (produced by Phytophthora), the spread of inoculum is only by physical movement of the soil. Presumably, beds remaining intact and in place, as they would be for second year strawberries or other system of minimal tillage, will keep the pathogen from being spread to non-infested parts of the field.
This situation has been observed locally. In 2013, a strawberry field had significant Macrophomina outbreaks in certain parts of the field. Held over for a second year, the dead areas were replanted and again developed disease in those sections; however, second year plants that were healthy in 2013 were mostly healthy in 2014. While growing second year strawberries is not being recommended, this type of situation demonstrates the key role of soil movement in disease epidemiology.
Sanitation: Sanitation is critical for limiting the spread of Macrophomina and Fusarium. Tractors, tillage equipment, and irrigation pipes moving from infested fields should be cleaned. Remember too that a strawberry field that had significant dieback two years ago and is now planted to lettuce or another crop, likely still has plenty of Fusarium or Macrophomina around. It is a good practice for all of us to pay attention to where we have been and clean up if you are coming out of an infested field.
Having the Right Attitude and Accept the Changing Reality: In this environment of new diseases and reduced to no availability of good fumigants, those able to keep open minds and adopt new practices stand the best chance to weather the storm from these new pathogens. Growers and agricultural professionals of all stripes MUST adapt to this new era. Go to meetings, keep up to date on the latest research, talk with reputable professionals and be ready to make the changes necessary to keep your crop the most productive it can possibly be.
Photo progression- Field with Macrophomina June 21. Photo by Steven Koike, UCCE.
Photo progression - same field as above with Macrophomina- July 5. Photo by Steven Koike, UCCE.
Photo progression - Same field as above with Macrophomina July 26. Photo by Steven Koike, UCCE.
Nice little article describing the collaboration between me and Steven Koike on solving disease and physiological problems in the strawberry industry. You name it- we take it on, solve it and post what we found out in this space so everybody can learn along with us.
Yellow, dying strawberries? Bring in team Koike- Bolda from UCCE and solve it.
California has emerged as the world's almond orchard because of near-perfect conditions for the crop, but in terms of production, it may have hit its peak, reported Jennifer Rankin in The Guardian.
"The future for farming almonds in California will always be there," said David Doll, UC Cooperative Extension farm advisor in Merced County. "It is more about coming into balance with our water resources."
The story quoted from a UC report that California farmers have spent an extra $500 million this year pumping extra water to cope with the drought.
Co-author of the study, Richard Howitt, professor in the Department of Agricultural and Resource Economics at UC Davis, cautioned against singling out particular crops.
"Don't blame almonds for the problem," he said. "The problem is one of water mismanagement."
He suggested changes in how California manages water so farmers monitor their groundwater use and replenish supplies when there is more rain.
"[The farmers] should be repaying what they are taking. And if they are taking more, as they always are in droughts, then they should be making plans to repay it back in wet years. If you treat your groundwater the way you treat your retirement account, then everything would be OK."
More information about water stress in almonds may be found in David Doll's blog, The Almond Doctor.
Because of the drought, California almond farmers have been forced to drill new wells, rely on salty groundwater for irrigation and bulldoze some trees, reported Robert Rodriguez in the Fresno Bee.
The story presented results from the USDA National Agricultural Statistics Service, which worked with state ag officials to send surveys to 688 California almond farmers; 458 of them responded.
The survey found that nearly 70 percent of almond farmers have only groundwater to irrigate their trees. About 23 percent said they had to drill new wells and 32 percent were reconditioning existing wells.
Normally growers mix surface water with groundwater to dilute the salts in water that has been pumped up from wells. But for many farmers, that hasn't been possible this year.
"Consequently, the amount of salt in the trees has placed them under stress and it is being reflected in smaller nut size, reduced growth and the potential for small crops in the future," said Bob Beede, University of California Cooperative Extension emeritus adviser who specialists in nut crops. He added that salt buildup can kill a tree.
2014 Plant Disease Seminar
Thursday, November 13, 2014
8:00 a.m. to 12:00 p.m.
**County of Monterey Agricultural Center— Conference Room**
1432 Abbott Street, Salinas, California
8:00 – 8:30 Registration for morning session (no charge).
8:30 – 9:00 2014 plant disease developments in coastal California
Steven Koike. UC Cooperative Extension, Monterey
9:00 – 9:30 Weeds as pathogen reservoirs: INSV case study
Richard Smith. UC Cooperative Extension, Monterey
9:30 – 10:00 Iris yellow spot virus of onion: coastal & statewide update
Tom Turini. UC Cooperative Extension, Fresno
10:00 – 10:30 Break: Sponsored by CAPCA, Monterey Bay Chapter
10:30 – 11:00 Challenges of spinach seed production
11:00 – 11:30 Biology of Fusarium oxysporum & management of
Fusarium wilt of lettuce
Tom Gordon, University of California at Davis
11:30 – 12:00 Pre-plant soil preparation post methyl bromide:
where are we going from here?
Mark Bolda. UC Cooperative Extension, Santa Cruz
Continuing education credits are requested. Call ahead (at least 24 hrs.) for special needs arrangements; efforts will be made to accommodate full participation. For more information, contact Steven Koike (831-759-7350; 1432 Abbott Street, Salinas, CA 93901) or visit our website at http://cemonterey.ucdavis.edu.
Requirement from California DPR: Bring your license or certificate card to the meeting for verification when signing in for continuing education units.