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.

The hot weather of this past week has unsurprisingly caused a certain amount of sunscald on caneberry fruit.   As can be seen in the photos below, sunscald manifests itself as a white to brown discoloration of one or more of druplets on mature and immature fruit.

The current round of sunscald has accompanied the hot spell of the past three days, and this is consistent with what we have witnessed in the past.  Any time on the Central Coast that we go from fairly steady temperatures in of 70^oF to suddenly around 90^oF with an absence of fog, we experience significant increases in sunscald.

While it may seem that the sunscald of raspberry fruit is caused by simply very hot weather, it is a little more complicated than that and it is actually radiation from the sun which is causing the problem.  Apparently, this radiation causes enough physiological changes within the fruit to discolor it, but not causing it to become necrotic right away.  Humid air, which in our area tends to be cool (think fog), scatters and absorbs radiation from the sun, while hot air tends not to carry too much of the radiation scattering moisture and therefore is not doing as much to scatter it and prevent it from damaging fruit druplets.  Windy weather is even worse, since it is moving the moisture out and away from the canopy.

There are several solutions to this problem.  One, the least practical, is to introduce moisture into the canopy via overhead irrigation.  It is best of course to do this in the early morning, to ensure that the flowers and fruit are dry by the evening.  Another is to use some form of shadecloth to cover the plants, which many Pajaro Valley growers are already doing to a certain extent in the form of macro-tunnels, where very little sunscald has been observed.   Finally, it is known that some varieties are more susceptible to sunscald than others, so if one is consistently having problems with sunscald, switching varieties might be a good solution.

A rather thorough presentation of one year’s worth of work on spotted wing drosophila was made at the big entomology meeting on September 13. As this presentation will not be posted anywhere, the following will be a summary of the work and what we know so far, along with some pointers that may be useful for growers to follow in their efforts to control this pest.

Along with various private industry efforts, the work that is being done right now by UC Davis and UCCE on spotted wing drosophila is important.  The California caneberry industry is 56% of the national fresh market production and has a production cycle on the Central Coast starting in April and continuing on until December, creating a situation of considerable potential of economic harm for this pernicious pest.

The trapping portion of this study tested two common bait formulations, yeast + sugar + water and apple cider vinegar, against a water control from late October 2010 to early September 2011.  We are still in the first year of the study so it is a bit early to draw conclusions, but over time the yeast + sugar + water perhaps performed a little better than the apple cider vinegar. Both baits tended to follow the same pattern meaning there was a period of no response to the traps (they caught very few adult flies) from late February to late May and a large increase of adult flies in the late season.  Additionally, there tended to be more females trapped than males. Whether this is a function of there simply being more females in the field than males or that the traps are simply more attractive to females remains something to be investigated.

Sampling for larvae which began mid-May of this year seems to indicate the first generation of larvae may appear before any noticeable adult fly population, and this continues later on through the season as larval peaks correlate with adult population peaks.  Larval and adult fly populations peak after the end of harvest, which only underlines that growers remove the crop as soon as possible after the cessation of fruit production.

A remaining target for us is the whereabouts of the population of spotted wing drosophila during the period of no response to traps (late February to late May).  We are not trapping flies in the fields, but obviously they start to come from somewhere when the season gets underway again in the spring.  We must understand what is going on here, as these stages of low pest activity tend to historically be the areas where the strongest measures of integrated pest management can be applied.

I was taken to several raspberry fields today to investigate an unusual and rather concerning plant disorder.  As one can see from the pictures below, leaves were significantly yellowed, with an abrupt change without regard to leaf venation from yellow to green in many cases.  Some leaves had fallen off, and severely yellowed leaves fell off at the touch. Within the field of yellow, there were many spots of green.  The undersides of the leaf were showing the same, but with the addition of fluffy orange spots throughout. The symptoms were widespread and affected the lower quarter to third of nearly every plant in the visited fields.  Clearly, this was fungal but the question was what fungus?

The literature does admit that downy mildew can occur on raspberries and even result in yellow discoloration.  However, this disease is always marked by purple blotches on the upper side of the leaf, and fluffy mycelial growths on the underside of these very spots.  Microscopic evaluation of several infected leaves today gave no sign of the telltale bunches of mildew mycelia and sporangia masses.  This disease is definitely not downy mildew, since few of the symptoms are consistent with this pathogen.

Rather, and this can be seen from the photos below, the masses of orange to yellow spores on the undersides of infested leaves had were typical of the rusts, and in many more advanced cases one could find the diagnostic teliospores of Phragmidium rubi-idaei, the causal organism of yellow rust.

The extent of leaf yellowing in the pattern depicted below is unusual.  Especially the sharp demarcation of green to yellow.  Short of the defoliation, the literature does not refer to yellowing of the leaf in association with yellow rust infestation.  This bears watching. 

Growers report that these symptoms have appeared very rapidly, and have advanced significantly over the past few days.  Rust spore germination is contingent on water, so that we have had a significant rainstorm followed by mostly cool weather since has a lot to do with the severity of this current epidemic, in my opinion.  

The rusts are controlled by a reduction of moisture.  One way is of course to increase air circulation in the hedgerow, but even better is the use of tunnels which sharply reduce the humidity on and around the plants.  The fungicides Rally and Pristine are registered and very effective against rust.  Organic growers have access to fixed coppers and oils.   All of these materials can reduce fruit yield if used excessively and too early on sensitive developing plant tissue, so growers should not strive to eliminate rust from the hedgerow with repeated fungicide applications, but rather just limit it's spread to the upper foliage where flowering and fruiting is going on.

There are several fungicides mentioned for management of rusts in this article.  Before using any fungicides, check with your local Agricultural Commissioner's Office and consult product labels for current status of product registration, restrictions, and use information.