It's official.  As of March 8, the Federal Order will be revised to reflect that blackberries and raspberries are no longer on the regulated host list for European grapevine moth.  What this means to you as person working in caneberries is that from here on out you will not be inspected for European grapevine moth.  The link to the revised Federal Order is below:

http://www.aphis.usda.gov/plant_health/plant_pest_info/eg_moth/downloads/spro/DA-2012-07.pdf

As stated before in this space, Canada is expected to follow suit in short order.

This was a team effort and it is time to give credit where it is due.  Thank you to Lucia Varela of UCCE, Santa Cruz County Agricultural Commissioner Mary Lou Nicoletti, Sam Cooley of Driscoll's, and Leah Gayagas and John Fergusen from the USDA. 

It's a beautiful day in the Pajaro Valley.

As many Central Coast caneberry growers know, this summer season has seen an astonishing number of lygus bugs in blackberries.  Counts of 10 to 20 lygus bugs per shake easily rival the heaviest infestations in strawberry.

However, contrary to the “catfacing” or misshapen fruit left by lygus activity in strawberry, there does not seem to be a documented type of damage from lygus in blackberry.  All the same, customers have been getting tetchy about having bugs in their baskets of fruit, so it is indeed important for us as an industry to take this on.

Unfortunately, management of lygus in blackberry has proven to be just as difficult in blackberry as strawberry, perhaps even more so since there are fewer insecticides registered for use in blackberries.

Thrips incidentally occur in blackberry flowers as well and did in great numbers in this trial.  Again it is not certain whether or not they cause a lot of damage.  Nevertheless, thrips were also evaluated in this trial since they are a known pest in other crops and situations.

The organically registered insecticides MPede and Aza-Direct have shown promise in controlling stink bugs (same insect order as lygus bugs), so the study described below is a screen these two materials compared against a grower applied standard of Diazinon along with an untreated control. 

Trial was composed of 4 24 ft x 26 ft replicated treatments in a blackberry field with significant lygus and thrips activity.  MPede and Aza-Direct were applied with a motorized backpack sprayer by Brian Deeter from Gowan Company.  Diazinon was applied at the label rate by the grower in an adjacent block, so while not part of the experimental design, it did provide reasonably strong information in comparison to the three other treatments. 

My research assistant and I did the evaluations which consisted of shaking 3 feet of flowering blackberry hedgerow into a five gallon bucket for the lygus and agitating three mature flowers individually onto a white sheet of paper and counting the expulsed thrips there.  Dates of evaluation were August 11 (pre-application), August 15 and August 19 (one week post application).

As the reader can see from the chart below, beyond Diazinon there is little effect on field populations of lygus or thrips from either MPede or Aza-Direct.  Furthermore, the lack of thorough control of lygus and thrips by Diazinon, long regarded as one of the most powerful pesticides available to blackberry growers, is unsettling.

Means followed by same letter do not significantly differ (P=.05, Student-Newman-Keuls)

Mean comparisons performed only when AOV Treatment P(F) is significant at mean comparison OSL.

Finally, it will be worth my while to return to this field to evaluate the effect, if any, this pest load is having on fruit development.  As already mentioned above, beyond the contamination of harvested fruit, thrips and lygus damage to blackberry has not yet been well defined.   

There are a number of pesticides mentioned for management of lygus and thrips in this article.  Before using any of these products, check with your local Agricultural Commissioner's Office and consult product labels for current status of product registration, restrictions, and use information.

We have had the misfortune of discovering Armillaria root rot on blackberry on the Central Coast.  This is significant in that root rots such as those from species of Phythophthora or Verticillium are extremely rare in blackberries cultivated in this area.

Generally known as a pathogen of forest trees and orchard crops such as apples and avocados, this root rot is known by the common name “oak root fungus” and is caused by several different species of Armillaria fungus.  The above ground symptoms of Armillaria root rot are those common to other root rots, that is to say wilt and stunting of canes and leaves (Photo 1 below).  Below ground, roots in blackberry show obvious signs of rot frequently accompanied with whitish mycelial growth (Photo 2 below).   While the literature also says this mycelium forms sheets and fans that was not the case in this particular situation.   Importantly, the symptomatic plants are found in patches which slowly advance outward over time.  In more advanced infections, one would also find black rootlike strands of 3-4 mm in diameter known as rhizomorphs.  In the situation addressed here on the Central Coast, the infected areas were limited to rows and tended not to cross over into the next, so the paucity of root growth and moisture in the area between rows may be limiting to disease spread from row to row.

Armillaria infections of blackberry are a result of previously infected orchard plantings.  Since this pathogen can persist for decades in infected stumps and other woody material, the history of a field should be of serious consideration for blackberry growers when looking at new ground to plant.

While it is undoubtedly a good idea to fumigate a piece of ground known to have been infected with Armillaria fungus, fumigation itself might not be enough because even the best fumigant may be hard put to penetrate infested stumps and other woody debris.  With this in mind, to the extent possible, remove woody debris from a cleared orchard or forest prior to fumigation. 

Once an infection is underway, the only way to address the problem is to limit the spread of the disease. This means removing symptomatic plants and as much of the roots as possible along with those plants immediately adjacent.   No, this will not eradicate the fungus from the plantation but will serve to at least limit its spread through the field to other plants.

The recent implementation of an eradication program and proposed quarantine of grapes of a small area in south Santa Cruz County due to multiple finds of European grapevine moth, Lobesia botrana, puts us in the position of having to discuss in detail the possibility that this pest could occur in blackberry.    

While blackberries are described in the literature as having been a host of European grapevine moth and thus will fall within compliance actions, I have reason to doubt that European grapevine moth will be found in our cultivated blackberry varieties here on the Central Coast because of the following:

1- The clustered inflorescences of grapes are quite distinct from those of blackberries, yet have been described as a major part of the attraction of grapes to European grapevine moth.  Blackberries occur in loosely formed inflorescences of less than 10 fruit, and are not in compare to the numerous, closely grouped fruit of wine and table grapes.   Simply put, the morphology of the inflorescences of cultivated blackberries in our area is not amenable to European grapevine moth.

2- The species of blackberries on which European grapevine moth was reported in UC and CDFA literature is given as Rubus fruticosus, which is the wild blackberry commonly known as Himalayan blackberry found alongside roads and in the woods.  Cultivated American blackberry cultivars do not come from this R. fruticosus, and rather come from R. allegheniensis, R. argutus, R. frondosus, R. ursinus, R. macropetalus and R. loganobaccus. 

3- The current campaign outside of species specific pheromone based mating disruption underway by area blackberry growers in eradicating the other invasive leafroller species, the light brown apple moth, from their fields will go a long, long way in keeping fields clear of European grapevine moth should it ever find its way there.

The link for the full provisional guidelines is here:

http://www.ipm.ucdavis.edu/EXOTIC/eurograpevinemoth.html

In spite of of the factors predicting very low odds of European grapevine moth infesting Central Coast blackberries, growers are nonetheless cautioned to be vigilant and are encouraged to contact this office should they have questions concerning this matter.