The following is regarding a sample of raspberry sawfly submitted to this office this afternoon. This sawfly, very likely Monophadnoides geniculatus, is not that common on the Central Coast but the infestation described to me was sort of acute.
As one can see from the photos below, the larvae of the raspberry sawfly are rather bristly and run around 10 to 13 millimeters in length. The damage is distinctive, consisting of a patchwork of holes on infested leaves. The literature describes leaves being skeletonized by raspberry sawfly feeding, but I have yet to see anything as severe here.
The important part for growers and consultants to know is that raspberry sawfly is a wasp, not a moth or fly. It belongs to the family Tenthredinidae in the insect order Hymenoptera, which derive the common name of sawflies from the ovipositor of the females which is adapted for sawing. The female raspberry sawfly inserts her eggs into the leaves in May, and the larvae emerge obviously right around now. They feed for two to three weeks after which they drop to the ground to form a cocoon, from which the adult emerges the following year in the spring. There is only one generation per year.
From a pest management point of view on the Central Coast, the incidental damage we see on the leaves will not harm the plant and by any measure the damage is short lived and limited to the two to three week feeding period. However, growers who are concerned about incidental contamination of the harvested fruit from a medium to heavy raspberry sawfly infestation may want to treat.
Thanks to the PCA and his apprentice for bringing these samples by the office this afternoon. It really helps me keep current on what is going on out there.
This comes up a couple of times every year so it is worth reviewing and certainly adds value to our catalogue of plant disorders on these berry blogs.
The following plant sample of a proprietary variety was received 4/24/2012. One can see immediately that the leaves are chlorotic and burnt at the margins and in some cases (photo 2 below) newer leaves are somewhat deformed as well. Most often one will encounter a pink tint to many of the leaves.
The situation in the field was as follows, a mixture of Round Up (glyphosate) and Shark (carfentrazone) was applied to the field to control weeds one month prior to planting. According to weed scientist Steve Fennimore, the Shark does not linger in the soil for any significant period of time, actually around three hours tops. On the other hand, Round Up can linger for a while, maybe even longer than a month especially in a sandy soil in which it is not adsorbed to fine soil particles as it would in a clay.
The solution to this predicament, and indeed in all cases of Round Up toxicity, is to let the plant grow out of it. Raspberries have substantial stores of carbohydrates to draw on and can usually overcome the temporary inhibition of photosynthesis caused by mild herbicide damage such as the case presented here.
There are several herbicides mentioned in this article. Before using any herbicides, check with your local Agricultural Commissioner's Office and consult product labels for current status of product registration, restrictions, and use information.
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:
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.
- Posted By: Mark Bolda
- Written by: Mark Bolda
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 70oF to suddenly around 90oF 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.
- Posted By: Mark Bolda
- Written by: Mark Bolda and Kelly Hamby
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.