- Author: Mark Bolda
Since we have had our first field closure in strawberry as of last night, it is important for us all to review how the USDA regulatory process unfolds for growers here.
Field closure is expensive and to be avoided. For readers who are not growers or familiar with commercial strawberry production, consider that the average weekly take out of a field can be 400 boxes per acre that we will conservatively price at 8 dollars a box back to the grower. So the weekly cost of LBAM closure to a fifty acre field is 160,000 dollars. Personally speaking, this enormous penalty is totally out of proportion with the infraction of having a quarantined pest in one’s field, but it is not my decision to make.
Cooler Inspection: USDA inspectors are to visit area coolers at regular intervals, my understanding is that because of the reduced budget for the program they will be checking in at each local facility once a month. This may change however depending on the vagaries of Federal budgets and politics. Once at the cooler, inspectors take a subsample from a load of fruit from each production field for that day. The inspectors are VERY thorough, the field closure from last night came from a larva tucked under the calyx. Unfortunately, such a larva often cannot be identified right away and so a hold is put on fruit coming out of that field. In plain English, that means the field is closed and you can no longer harvest and send fruit out of that field.
Field Inspection: Once a field has been identified as possibly infested with light brown apple moth, the next step is for inspectors to do an inspection of the field itself. I have seen field inspection, and it does not leave one leaf unturned. For somebody with experience, leaf rolls are easy to see, and inspectors walk with up to six people abreast, one person per row. Since this is their job, day in and day out, they are really good at it and if you have a leafroller, it will be found.
Treatment of Infested Fields: If no leafrollers are discovered during the field inspection, the field is opened back up. If a leafroller is discovered and furthermore found to be positive for LBAM, the grower is mandated to make an application. He or she chooses from a list of allowed materials, and fortunately this year, according to program director Rick McKay, surfactants and adjuvants are allowed and highly recommended. All parts of the application are observed by inspectors from loading, mixing and the actual spray. Nothing says that the grower can't be making applications before and after this regulated application, but they need to see the one they mandate. Then, depending on the pesticide used, inspectors return after a specified number of days to re-inspect the field. If no more leafrollers are found, the field is opened back up. If a leafroller is found, the field remains closed and the application procedure is repeated. Experience from last year says more often than not it takes more than one spray to re-open a field. In some cases, especially in organic fields, which have a much narrower selection of effective materials, it can take more than a month to re-open.
Discussion: It is imperative that growers pay attention to leafrollers in their fields. Yes, they are around, because I have been getting phone calls about this all week long now. Conventional growers have a wide range of materials at their disposal, organic growers less. It is not a bad thing yet to be putting out the pheromone mating disruption twist ties, since we are probably looking at a flight of adult moths in late June, with a subsequent larval infestation in July and August again. In light of the devastating costs of field closure, it might not be too much to have crews go through the fields regularly and be removing rolls.
- Author: Mark Bolda
This is a revision from the previous post:
A couple of samples handled by this office from strawberry over the past two weeks have turned out to be a leafroller species which might not be light brown apple moth. Probably the reason people have been asking about these is the general concern about having leafrollers in one’s production field at all. This is understandable, considering the current regulatory environment which mandates closure of at least part of a field on discovery of one species of leafroller; the light brown apple moth. Fields can also be temporarily shut down as regulators work on distinguishing leafrollers from one another in order to get a positive light brown apple moth identification.
The following short description will be about garden tortrix in strawberry.
This very important for those making a definitive identification in the field. While the UC IPM guidelines refer to garden tortrix as having a "spot on the back of the head" this spot is actually a darkened prothoracic shield behind the head on not on it (see fourth picture below). I would very much like to get a definitive sample from our area of garden tortrix for a clear picture for this blog, so will ask my readership to bring any suspect samples. It would be very helpful.
- Author: Mark Bolda
The pictures below are of a sample submitted today of physical damage to raspberry cane. Apparently this problem occurs across all varieties and areas more or less to the same degree.
Closer inspection of the affected canes reveals that the brown areas are very thin and indeed when one peels it back with a razor blade it is no thicker than a millimeter or two. There is no damage any deeper, nor are there signs of fungal or bacterial infection of any sort.
The diagnosis of the problem is that this was caused by a period of unfavorable weather, perhaps wind, sun or cold. Since it is being described as being distributed so evenly across different varieties, it must be something that imposed itself from without at the same magnitude, of which unfavorable weather can really be the only one.
That said, this issue certainly bears watching, and if it becomes worse I would appreciate readers bringing in some samples or calling me out to the field.
4/26/2011 Update: It seems further visits to the field turned up a large number of snails, probably stemming from the high levels of moisture we have experienced of late. The damage seen on these laterals would be consistent of course with the scraping feeding of snails. If one is concerned about the level of damage, there are baits for snails, but the current warming trend and drier weather is going to do much to reduce their numbers as well.
- Author: Mark Bolda
Blackberry growers in the Pajaro Valley should be aware that there are substantial numbers of light brown apple moth (LBAM) larvae active in many fields right now. The photos below outline what this pest looks like and what it is doing right now in our blackberry fields.
In the photographed field, there were on the order of 7-9 leafrolls per two feet of hedge in the heaviest infested areas and in excess of 80% of the leafrollers sampled in the photographed field were identified as having a very high likelihood of being LBAM. This is very concerning, since under the current quarantine enforced by the USDA, the presence of any leafroller in a field can be cause for significant delay of harvest much less outright field closure if an LBAM is found.
While clearly not the level of devastating 100% loss of harvest caused by field closure for a positive LBAM find, LBAM itself is also capable of causing some damage. As one can see from the photos below, damage ranges from incidental feeding on flowers resulting in blemished (thus unmarketable) fruit to heavier feeding causing abortion of entire laterals and the subsequent loss of fruiting potential there. In the field photographed below there was damage of some sort to one of every sixteen fruiting laterals.
Anecdotally, it appears that growers who kept up with changing out pheromone based twist ties every four to six months have very low populations of LBAM suspect leafrolls, while those who allowed pheromone coverage to expire before putting up a fresh set are tending to have heavier, in some cases very heavy, larval infestations. If one is not going to be using pheromone based twist ties through the entire year, it is at least a good idea to put out a few pheromone traps to find out when adult males are starting to fly and looking to mate so as to better target use of mating disruption techniques.
As it seems many of the larvae being discovered currently are in the fourth to late instar stage (½ to ¾ inches in length), applications of Bacillus thuriengiensis formulations will not prove to be very effective. Better materials are the spinosyns, one of which (Entrust) is registered for use in organic fields, and bifenthrin (hard on beneficials though). Addition of a good surfactant is always a good idea to break spray water surface tension to facilitate movement of material into even the tightliest wound leafroll.
There are several insecticides mentioned for control of light brown apple moth in this article. Before using any insecticides, check with your local Agricultural Commissioner's Office and consult product labels for current status of product registration, restrictions, and use information.
- Author: Mark Bolda
This article is to share some information regarding orange rust in blackberries on the Central Coast. Apparently, this fungus was detected last year and it continues to spread. Previously only seen in some local plantings of Chester blackberries it has now been found on several occasions in proprietary blackberry plantings. Orange rust is a tough disease to deal with, so it is worth being able to identify and knowing what steps one needs to take to mitigate its spread.
Orange rust is caused by two fungi, Arthuriomyces and Gymnoconia which are distinguished by the shape of their spores and life cycle length. Their growth is favored by cooler temperatures and high humidity. While it is not common that orange rust infected plants die outright, their ability to produce fruit is severely compromised.
As readers can clearly see in the photos below, orange rust is hard to miss in the field. From further away, infected canes have a spindly appearance and on approaching one will see the upper leaf margins of both primocane and floricane framed with the distinctive orange of the fungal infection on the underside of the leaves.
Of all the rust fungi that we deal with in caneberries on the Central Coast, orange rust is unique in that it grows systemically in the plant, meaning that the most important management tool for growers dealing with an infestation of orange is a shovel. There is no effective fungicide for orange rust. Infected plants should be removed entirely, meaning all canes, leaves and the roots. This is best done before the pathogen spores are ready to be spread by rain and wind in mid-April through May.
