- Posted By: Mark Bolda
- Written by: Mark Bolda
There have been a few reports as of late concerning a rather abrupt wilting of blackberry plants in certain fields. Some of these wilts have been found to be caused by raspberry crown borer, which merits a discussion of this pest in this space.
Crown borer is actually simple to diagnose in the field. One will notice a rather pronounced wilt of the plant, and a subsequent evaluation of the crown of the plant will find a hole there, usually with some sawdust like material deposited outside. Excavation and opening this section of the plant will find significant tunneling and usually a rather large larva of a half an inch or longer in length, which of course explains the wilt, since most of the water conducting elements are ruined by all this activity and no longer functioning in bringing water higher up to the plant.
As the reader can see from the picture below, crown borer adults look a lot like a wasp, but they are not. They are a clearwing moth that looks like a wasp to protect it from predation. Note the long antenna and extensive scales on the individual that distinguish it from a regular wasp in the picture below.
Briefly, the life cycle of crown borer is two years long. It appears that the adults are active here in Watsonville in late June and so they would be laying their red-brown eggs on the undersides of leaves around this time as well. Larvae, after emerging from the eggs somewhere in the area of a month later, work their way down the cane, where they either find a place in the bark to hide or begin excavating a tunnel in the crown. In either case, the larva is not embedded in the cane yet and rather shallowly situated. The larva continues to tunnel into the crown through the following year, by the time which the damage can be quite extensive. Late in the summer, the larva must go into pupation, a state which it apparently remains in until the following spring. There is unfortunately no degree day model available for raspberry crown borer yet- this would be an exceedingly useful tool, since we are able to use pheromone traps to detect emerging adults and would be able to count with fair accuracy when the susceptible larvae are emerging and working their way down the cane.
A test using drenches at the base of the cane (Johnson and Kim, 2011. The Bramble pp 8-9) found that Brigade, Assail and Entrust all reduced the amount of crown borer in infested caneberries. Altacor, also registered in caneberries, has also been recommended for crown borer but it is not clear how well this worked in controlling them. These applications are a function of how closely one is to getting the small, superficially hidden larvae of the first year after they hatch. The deeply embedded larvae of the second year would be near impossible to get to and kill, by my estimation.
It is still my recommendation that crown borer infested plants be removed immediately from the field and destroyed. I have yet to see an infestation that is extensive in a field, so plant removal is essentially rouging and keeping the populations of this still rather infrequent pest in check rather than reducing yield by large scale plant removal. This is important, since blackberry plantations tend to be long lived, and maintaining them as clear as possible of crown borer is a good step in the direction of maintaining long term field viability.
There are pesticides mentioned for management of raspberry crown borers 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.
Thank you to Chris Matthews and Doyle Goins for their assistance with the information for this article.
- Posted By: Mark Bolda
- Written by: Mark Bolda
Starting Friday and over the weekend, a number of area blackberry growers have reported high numbers of lygus bugs in their fields. I checked on one field this morning, and indeed the level of infestation is astonishing. Somewhere in the area of ten early stage nymphs can fall out from a few shakes at a single spot at any number of points all across the field. This is without precedent in any type of berry and merits some thought and discussion.
The field that was viewed this morning was in full harvest with a lot of fruit in the yet green to pink stage. Primocane was still growing vegetatively with no flowering. I do not think lygus presents any harm to the quality of the fruit or the vegetative plant, other than as an incidental contaminant in the baskets of harvested fruit, much along the lines of what we have recently seen with stinkbugs. Lygus bug feeding damages the flower and developing fruit, so once the druplets have made and the fruit has formed, these bugs will no longer be able to harm it. Since the field examined today has next to no flowers, the nymphs must be feeding on sap from the newly developing vegetative tissue. Whether this causes harm to the plants remains to be seen.
Beyond the contamination of harvested cited above, the possibility that this colossal lygus population shifts over to later bearing varieties which are entering into flowering would give some reason for concern.
Fortunately, blackberry growers have several options available to them to control these pests. One of the best combinations we found from our work in managing lygus in strawberries has been a pyrethroid + neonicotinoid applied when the lygus are very small as they are now. Always bear in mind that this powerful combination of pesticides will weigh heavily on beneficials. Additionally, the neonicotinoids registered in blackberries present some issues with maximum residue limits (MRL's) to fruit exported to Canada.
Organic growers have few options short of border weed removal and vacuuming available to them unfortunately.
There are pesticides mentioned for management of lygus bugs 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.
- Posted By: Mark Bolda
- Written by: Mark Bolda
As many readers know by now, raspberries destined for sale in Canada have been included in the European grapevine moth (EGVM) quarantine. Raspberries are on the host list for European grapevine moth in Canada (but not the USA) and quite likely this has something to do with the rather nebulous description of Rubus spp as being a host in one or more older papers (like early 1900's sort of old) on this pest. Raspberries are Rubus ideaus, while blackberries arise from a wide number of species within Rubus.
Currently, raspberry growers within the quarantine area, loosely described as being to the west of Green Valley Road, Dalton Rd and on out to Casserly (see attachment below), are not eligible to ship into Canada.
At any rate, the USDA Project will not be inspecting raspberries within the quarantine, they will only continue to inspect blackberries. Raspberries within the quarantine that would be eligible for export to Canada will be undergoing inspections and subsequently be issued compliance agreements next week by County Agricultural Commission personnel. I do not yet know how this inspection will be done, but we will find out that out very early next week.
7/6/11 Update: It looks like shippers who have raspberry fields within the EGVM quarantine area from which they want to export fruit to Canada would be subject to the same inspection regime as for all blackberries- ie 20 lbs of fruit from 40 acres of raspberries. These fruit would be inspected by County Agricultural personnel rather than USDA personnel.
It is of course very advisable to growers that they keep their fields clear of leafrollers to the extent possible.
So, questions about export of blackberries should be directed to the USDA Project 796-9699 and questions about the export of raspberries should go to the Santa Cruz County Agricultural Commissioner's office 763-8080.
EGVM quarantine boundary
- Posted By: Mark Bolda
- Written by: Mark Bolda
A few more comments on the situation with European grapevine moth in blackberries:
1- European grapevine moth is a surprisingly small moth, as one can see from the picture below. The larvae are also very small, so if you find a leafroller longer than a quarter inch in your blackberries, it is assuredly light brown apple moth or another leafroller and not European grapevine moth.
2- More information on the slim possibility of blackberries as a true host of European grapevine moth. Colleague Lucia Varela has provided me with a paper from the European Journal of Entomology (Stavridis, 1998) finding that European grapevine moth larvae did not survive when reared on blackberry fruit or flowers, but then a doctoral thesis from the Université Bordeaux 2 in 2002 identifies Rubus as a potential host. One of the crucial pieces of evidence for this identification is a book written by a P. Marchal in 1912, which we have not been able to find in order to confirm the citation as legitimate (if any of the readership here knows of a copy please let me know! It's pretty important). Underlining the dubiousness of the blackberry-as-host hypothesis, researchers in Europe, where this pest is native, have never seen European grapevine moth on many of the hosts cited in the work above.
3- A number of fields have been inspected, and as expected all have been found to be negative for European grapevine moth. Additionally, as a testament to the success area blackberry growers have had in controlling light brown apple moth, I have not heard of any finds of that pest either in these inspections. The regulations have been modified a bit now so that growers being inspected for European grapevine moth every thirty days are considered as inspected for light brown apple moth at the same time.
The photo below is of the inspection process (which takes from 20 to 30 minutes), and, as described before in this space, it is fruit by fruit. The inspectors are professionals, very thorough (and friendly too) and there is no doubt they will find larvae if they are present.
- Posted By: Mark Bolda
- Written by: Mark Bolda
As previously noted in this space, European grapevine moth has been found in this area and there is some regulatory action directed towards it. Blackberries, while an unfavorable host for European grapevine moth, are still identified by regulatory agencies as a host and thus subject to regulatory activity.
The following description of what regulatory activity in blackberries is going to look like was kindly provided to me by Leah Gayagas from the USDA PPQ.
A 5 mile radius of regulatory rigor has been drawn around the initial two European grapevine moth finds on Pleasant Valley Road. For us in the berry business, blackberries are the only ones identified as possible hosts, so raspberries and strawberries are not included in this list and are not of concern.
Currently, what this regulatory activity means for blackberry growers in this 5 mile radius is that there will be inspections of their production fields.
In field inspections will consist of the grower assigning some of his or her pickers to retrieve at least 20 lbs of harvestable fruit from a pattern which covers the whole field, which would probably consist of a trip around the perimeter of the field and then a ‘Z’ pattern on the inside. Considering what is at stake here, it would be best for the grower to assign the best of his or her crew to this assignment to make sure the very best of the field is harvested.
Harvested fruit are then lain out on a table and closely inspected by USDA personnel.
What follows is quite important:
Any suspect leafrollers from this 20 lb minimum fruit sample are forwarded on to the identification lab in Sacramento, be they light brown apple moth, orange tortrix or European grapevine moth or whatever- it all goes. In the very, very unlikely event of the collected leafroller being European grapevine moth, the field will be closed. In the unfortunate event that the leafroller is light brown apple moth, the field will be subject to a hold and then have inspection and pesticide spray protocols applied as has been standard for this pest. So, growers in the area currently under the 5 mile European grapevine moth inspection radius should be aware that are also in effect being inspected in the field for light brown apple moth.
Please be on your toes people!
