I have an ongoing study with an alternative fumigant (not chloropicrin) compared to an unfumigated control up against the methyl bromide/chloropicrin standard.   There's some other stuff in here too, that will be discussed at a later date.

The collaborating grower observed a few weeks ago that plants in the unfumigated control and alternative fumigant were going yellow, in particular the older leaves.  That this was not occurring to any sizable degree in the methyl bromide standard was notable.

As many of you my readers know, I really frown upon the identification of leaf yellowing as being caused by this or that deficiency in the absence of any sort of laboratory analysis, so I took two leaf samples from each of the three treatments and submitted them to Perry Labs here in town. 

Table 1: Average of two leaf blade samples from unfumigated check,  alternative fumigant and methyl bromide standard

Remembering that two samples per treatment aren't going to give us a what can be called a truly scientific conclusion, these results do at least give us a look at what is going on.  First of all, the yellowing probably isn't from nitrogen, which is showing up very much at sufficiency in all treatments.  Ditto Ca, Mg and the micros (note that original sample Fe numbers are all over the place); Na is low.  

Circling back, we do see that P is lower in both unfumigated and the alternative than the methyl bromide standard, plus the symptoms show up in the older leaves, which checks out for a very mobile element like P.  K is just under that recommended from the revised nutrient guidelines from the work I did with Tim Hartz at UC Davis.  Additionally, P and K, which come into contact with roots via diffusion in the soil solution (meaning the roots need to grow to the minerals since they are both pretty immobile in the soil) as opposed to mass flow as is the case with nitrate (meaning the nutrient moves to the root since it is mobile), could have their uptake rates reduced by a lessened abundance of roots and root hairs.  

The question is then if what we are seeing here is that the lower root growth stemming from less than accustomed fumigation efficacy is also a cause of an apparent deficiency in phosphorous and maybe potassium. 

This is an announcement for the Annual Strawberry Field Day held by colleague Surendra Dara in Santa Maria, California, this coming May 6.  It's always been a good event, very well worth the time to go!

http://cesanluisobispo.ucanr.edu/files/209810.pdf

I was called out last week to evaluate the following situation, which I am sure is not at all unfamiliar to any of you who spend time working with raspberries under tunnels. Symptoms, as shown in the pictures below, consist of very obvious yellowing, sometimes half the leaf, sometimes less, sometimes more, started a few days after the tunnels went up and a run of hot days.

Consistent with the work we have done on this issue in the past, it's fairly clear that the leaves are dying from the high temperatures in the newly erected tunnels. The elements nitrogen, phosphorous and potassium are being remobilized from the yellow leaves to newer leaves on the plant, while others, markedly calcium, are left behind or continue to accumulate (look at the large differences between iron and boron in healthy green leaves as compared to yellow leaves). Curiously, copper trends high in both – usually I see that around 2 or 3 parts per million.

Recommendation to the grower last week when I took the samples was to vent the tunnels by moving the plastic up a bit, and happily he reports an improvement in the plants already. 

Growers and pest control advisors on the Central Coast should be alerted to the gravity of the current leafroller situation.  Owing to a warm winter, large numbers of leafrollers, including light brown apple moth (LBAM), have been observed throughout the Monterey Bay area. 

Berry growers need to be diligent in using best pest management practices for leafrollers (given in other posts on this blog as well as the UC IPM website) right now to prevent additional field shutdowns and regulatory scrutiny.  The issue is particularly important for organic berry fields where worm control tactics are limited.

This is a very big deal, because the USDA – CDFA regulatory effort is still in full swing.   If LBAM is detected in a shipment, it could very well result in field closure for a long period of time, handing eye watering losses to the grower.   Very much worth paying attention to the matter of LBAM on the Central Coast.

In the way of review, growers shipping should have a compliance agreement issued to them by the County Agricultural Commissioner.   Harvested fruit is inspected on a monthly basis at the cooler, and if a suspect LBAM larva is found, the shipment is held up.   An investigation is launched during this time to  confirm whether the larva is actually an LBAM.  During this time, no fruit may be moved from the field that was the source of the lot.    Results may take days to get back, and if it is confirmed to be LBAM by DNA laboratory analysis the USDA- CDFA people will visit the grower for an inspection of the block or field where the larva was found.  It is very important to note that while the grower is waiting for results to get back on a suspect larva, he or she should be very active in cleaning up the field - pre-emptively treating with insecticides and removing leaf rolls. 

If on inspection more larvae are found in the field (they don't miss many, your threshold of detection is very low), the field is shut down for shipment outside the area of quarantine, and regulatory sprays must be done and need to be repeated until inspections find ZERO suspect LBAM larvae in the field. Regulatory sprays have to be witnessed by USDA or CDFA personnel.  The whole process can take a month or longer, when one figures in delays, shortage of inspection personnel and mandated limits on work hours for state and Federal employees. 

Further elaboration on the inspection protocol can be found here:

http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=4993

Compliance agreements issued to growers require weekly inspections (every seven days) for LBAM of the production field by a PCA or qualified scout.  If this weekly scouting is not done or records of it not kept, a grower having a positive LBAM find (starting 30 days to harvest for export to British Columbia, Canada) will be in violation of the compliance agreement.  This will result in the compliance agreement rescinded (ie taken away) and the possibility of a hefty fine.

PCA's are busy professionals, and sometimes the weather doesn't comply it might be difficult for them to get to the field every seven days. That's why it is so important for the grower to have qualified scouts on the farm doing weekly LBAM inspections (they are not difficult).  Mark has held a number of trainings already, and will hold two more trainings; one in English on May 28 at 8 am at the UCCE office, 1430 Freedom Boulevard, Suite E (same office as before) and another on May 29 in Spanish at 8 am at the same location.  The trainings aren't long, tops maybe an hour after which each participant will receive a signed certificate of participation.  If you need help with management of leafrollers right now, you can contact Mark (mpbolda@ucanr.edu), or Hillary (hthomas@calstrawberry.org), directly to provide additional resources or to consult with you on the site specific issue, risk factors, and management options.

In short, yes, it's important to pay attention to leafrollers in your fields this year.   Additional information in English and Spanish is included in this Green Sheet from the Commission that went out on February 18, 2015:

http://reports.calstrawberry.org/Reports/Green%20Sheets/02.18.2015_LBAM%20Advisory.pdf