Got a rather lengthy text from a colleague this afternoon concerning J rooting of strawberry plants - question was: does it really make a difference whether or not a strawberry transplant is J rooted?
Let's go to the Green Sheets, which have been a real treasure trove of information.
The one included in the link below was a summary of field work done by the late Warren Bendixen, who served as the Farm Advisor in Santa Maria for many, many years:
This work was done by Warren in response to a shift going at that time in Santa Maria from 40" inch beds with 5- 6" deep planting slots with very little J rooting to the 64" beds so familiar today, but with planting slots which would result in a lot of J- rooted plants.
Key takeaway from the paper, it's in bold because it's so important.
Plants with J roots reduced fresh fruit yields by 18.5%.
If this doesn't get your attention as to why we shouldn't be J rooting, I don't know what will.
The link below is to a paper written by Doug Walsh, Frank Zalom, Doug Shaw and my predecessor Norman Welch. It succinctly makes the point that a warm fall following transplanting decreases plant vigor, encourages precocious bloom and can predispose strawberry plants to infestation by twospotted spider mites. Rain can reduce overwintering mite populations, but still warm fall temperatures will decrease plant vigor.
With the understanding that this fall and winter has more than even odds of being an "El Niño" year (http://www.elnino.noaa.gov/), which could result in warmer temperatures and more precipitation, growers and agricultural people might want to be thinking about being a little bit longer than customary on cold conditioning of the day neutrals up here on the Central Coast.
Nice introductory video from Dr. Chieri Kubota with the Arizona Controlled Environment Center at the University of Arizona.
Lots of advantages in Arizona for hydroponics - no pesticides, winter production, less water use and SAME DAY delivery from the greenhouse to the store. At five bucks a pint not that cheap though.
Interesting history of strawberry production in Arizona, including the cultivation of an everbearing variety all the way back in 1893.
A recent article referred to one of the reasons that growers need access to new strawberry varieties is that there is an inherent loss in vigor through the propagation process. That growers need access to new varieties to remain competitive is absolutely true, but that they need access to new varieties because the existing ones decline in vigor is not.
Plants do not invariably “lose their pep after years of cloning”. Indeed, reputable nurseries avoid a loss of vigor in a variety by periodically going back to meristem culture in order to keep their plant stock strong and productive. It does happen (especially in some formerly popular caneberry varieties - compare Ollalieberry in the field today to what was around in the early nineties) that older varieties of less demand don't have the meristem work done as frequently and subsequently become less vital over time.
What is meristem culture? Meristem culture is the excision of a cluster of actively dividing cells from the meristem (tip) of a newly formed strawberry runner, followed by surface sterilization, placement on a special medium, subsequent rooting, gradual acclimation of the new plant and transfer to a secure greenhouse. While some cases of genetic instability from repeatedly doing meristem culture have been noted in the literature, this cannot be described as a drift towards a loss in vigor of a variety. At any rate, programs for production of true to type (identical) plant stock using meristem culture have been used for a long time at any of the strawberry nurseries in business today.
A good example of how well and long a popular variety can be maintained through meristem culture would be the strawberry variety ‘Chandler'. Chandler continues to be widely planted by direct marketers because consumers just love its flavor and quality. Consider though that this variety was patented in 1984 by the University of California, and has had no apparent loss in vigor in all this time because the nurseries continue to go back to meristem culture to maintain it.
Growers have rumored that the variety ‘Albion' has been losing its vigor, but work at the Pomology Field Station in Watsonville over several years shows that this was not at all true. The Albion grown at this field station has experienced NO loss in yield since it was first released. Rather the rumored "loss in vigor" of the very widely planted Albion is almost certainly because of the industry wide steady drift away from methyl bromide fumigation to less effective alternatives like 1,3-D and chloropicrin.
- Author: Steven Koike
- Author: Mark Bolda
- Author: Tom Gordon
2014 strawberry alert: Statewide, the California strawberry industry is grappling with two soilborne diseases that are spreading throughout the state: charcoal rot and Fusarium wilt. Both problems have been found in the Monterey-Santa Cruz region, and until recently most outbreaks were caused by the charcoal rot pathogen, Macrophomina phaseolina. However, in 2014 a number of new plant collapse cases were confirmed to be Fusarium wilt; overall, more Fusarium has been detected in 2014 than Macrophomina, a switch from previous seasons.
Symptoms: Symptoms of Fusarium wilt in strawberry consist of wilting of older foliage, plant stunting, and eventual collapse of the plant (Figures 1, 2, and 3). When plant crowns are cut open, internal vascular and cortical tissues are dark to orange brown (Figure 4). Disease is often most severe if the infected plant is subject to stresses such as weather extremes, water stress (excess or shortage of water), poor soil conditions, or heavy fruit loads. It is important to note that Fusarium wilt symptoms are virtually identical to those caused by charcoal rot.
Biology: Fusarium wilt is caused by the fungus Fusarium oxysporum f. sp. fragariae.This pathogen is host specific to strawberry and apparently can only infect this crop. The fungus survives in soil for long periods by producing resilient, microscopic structures called chlamydospores. The development of Fusarium wilt has been associated with changes in the practices of pre-plant soil fumigation. The fungus is spread within and between fields mostly by the transport of contaminated soil during soil tillage and preparation operations.
Current year management: For planted fields currently in production, there are no reliable control options for this disease. Because Fusarium wilt is more severe and develops more rapidly if strawberry plants are stressed, growers should manage the field so as to reduce stress; such steps include proper irrigation scheduling and the controlling of mites and other pests. Applying extra water will not help symptomatic plants. Even in the absence of stress, plants showing collapse symptoms eventually become non-productive.
Long term strategies: Integrated disease management strategies for subsequent crops involve the following: (1) Crop rotation. Do not plant strawberry in fields having a known history of the problem and avoid back-to-back strawberry plantings in infested locations. (2) Pre-plant fumigation. Such applications remain a useful tool for managing Fusarium and the other soilborne pests, even though most currently available fumigants are not completely effective. If fumigants are bed-applied, the level of control may be further reduced because of incomplete treatment of the soil. Measures that improve distribution of fumigants such as increasing the number of drip tapes may be beneficial. (3) Avoid stressing the plants. Stress will hasten the development and increase the severity of symptoms, so use appropriate growing and irrigation practices to reduce stress. (4) Sanitation. Growers with Fusarium infested fields need to be concerned with limiting the spread of the fungus from infested to clean fields. Being a soilborne pathogen, F. oxysporum can readily be spread by mud and dirt adhering to equipment and tires. Note that the pathogen may be resident in a field for several years before any plants show symptoms. Therefore limiting movement of soil between fields is a good practice even where no disease is evident. (5) Resistant or tolerant cultivars. UC cultivars show significant differences in susceptibility to Fusarium wilt, although none are completely resistant. San Andreas, Ventana, and Portola appear relatively resistant but reaction to the pathogen may differ year-to-year, which may be due to the variable effects of stress. Camarosa and Albion are both highly susceptible to Fusarium wilt.
Diagnosis and disease trends: Because Fusarium wilt symptoms are identical to charcoal rot symptoms and are similar to those caused by Verticillium wilt and Phytophthora root & crown rot, field diagnosis is impossible to accurately achieve. Submit strawberry collapse samples to the UC Cooperative Extension diagnostic lab in Salinas, which is supported jointly by UC and the California Strawberry Commission. Our research and extension team is closely following these disease developments; contact us if you see new outbreaks of these important problems.