It is most likely brown rot. Lots of wet weather brings that on. It can also later infect your peaches. I had some brown rot in one of my cherries and today I picked out all the rotting fruits so it would not infect other things. Spraying per se may not do any good at all, it all depends what you are spraying with. Get some Monterey Fungi-fighter if its brown rot, it is highly effective against that disease. The standard orchard sprays usually contain captan and it is not very effective against brown rot.

Scott

Spray or no spray, you get all the rain we just went through and the cherry crop is going to be minimal, I think. It will be interesting to see if the commercial guys pull anything through.

i don't think its brown rot, because the tree itself is very healthy, and i sprayed at blossom time with captan. also the fruit is not mature yet and doesen't the rot show up on ripe fruit?

It can show up earlier.

Any chance of pictures?

The cherries don't have to have brown rot for the trees to give up on them. When you get continuous cool wet weather immediately after set some varieties and species will lose their fruit. It takes a lot of energy to make fruit and not all can do it with stored energy.

I had many immature cherries rot this year so it definitely can show up earlier. Brown rot likes sugar so it is true that it is more likely to show up later, but if the conditions are right it can show up early. I have also already picked off several dozen rotting peaches and plums this year as well, same deal. Picking off the fruits is a good idea if only a small minority are infected as it will limit the spread of spores.

As I mentioned in my original post above, Captan is not a very good spray for brown rot, a fact that has been confirmed in numerous scientific studies.

Scott

"As I mentioned in my original post above, Captan is not a very good spray for brown rot, a fact that has been confirmed in numerous scientific studies."

Scott,

I agree SI's generally offer better control of non-resistant brown rot, but I think your assessment of Captan may be a bit harsh.

Cornell rates it 3 (out of a possible 4. Three is a good rating, 4 is excellent.) The Midwest Spray guide rates it a tad lower at a fair to good rating.

I've found Captan to provide good control of brown rot. It also has the advantage of low risk for resistance buildup due to it's multiple modes of action against the fungus.

Studies also show it has decent adhesion during rain. In my experience it adheres a little too well, as it leaves a film that can be difficult to wash off. For this reason I don't plan to use it close to harvest if at all possible.

Captan spray must be buffered or it breaks down rapidly. I'm convinced some of the problems associated with Captan to control brown rot are due to spray water being too alkaline.

Way I see it, studies can be very misleading because research trials fail to take in the whole picture on the ground. The difference between pesticides with kick-back and those that are only preventive is huge for the non-researcher but the advantage may not show up in research.

The SI's have kickback, Captan does not. If you fail to protect the fruit for a single day with captan your harvest may be toast whereas Monterey Fungus Fighter, Indar and the like can rescue a crop not only infected but where some fruit is already completely rotten.

Olpea, you can say what you like about rainfastness of Captan, but the only commercial grower I regularly talk to is always out there during light rains doing Cap aps. The SI's have liberated me from having to do this kind of thing. It's not just kickback but also being systemic, as of course, you know.

Resistance is an issue primarily for commercial growers,IMO, and in small stands of fruit trees it seems to take much, much longer to be a factor.

The same goes for insecticides and one reason Imidan is so effective in a low spray program is because of its ability to reach back and kill eggs already in fruit. Most of the info on various pesticides fails to include this important attribute of certain insecticides and fungicides. It's not even on the labels.

Harvestman, every research study I have seen puts Captan several rungs below the others, these are field studies which should portray what is happening on the ground. So I think in this case the researchers have it right (not always though!). Olpea, I think the midwest spray guide is accurate: fair to good. When pressure is light that will work but not this spring unless you are spraying it all the time. I looked at the Cornell guide and the footnote on brown rot states that captan is generally less effective than the better sprays. I couldn't find any table of efficacy.

Scott

Hman,

As I said, I agree SI's generally offer better control than protectants. The problem with SI's is their very limited number of uses.

For example, Bumper can only be used around bloom for blossom blight and then a couple pre-harvest sprays for fruit rot.

I know one Indar spray per season works for you, but here I can't rely on one or two pre-harvest sprays. Our season is just too long and the pressure too high.

I simply disagree Captan is easily washed off. All I've ever read suggests it doesn't, which mirrors my own experience.

Unlike the grower you mention, I don't fill up the sprayer to specifically go out and hit the orchard with Captan. Rather when I have to apply an insecticide, I generally tank mix a protectant fungicide with it. It keeps the overall innoculum down as well as providing some residual on the skin, so that when the skin gets nicked (for various reasons) it can heal before disease sets in.

Captan also fights scab, which although little concern for most backyard growers, is a concern for me.

Scott,

I interpreted Cornell's comment on Captan to refer specifically to sweet cherries which had to do primarily with the height of the trees (i.e. The compound being too diluted on such a large tree mass to provide adequate control.)

It says,"Sulfur, captan plus sulfur, and ferbam plus sulfur do not provide adequate control on sweet cherries. The maximum allowable rate of 4 lb/A for captan is inadequate on trees greater than 10 ft tall, particularly on sweet cherries."

Below is the link to Cornell's Stone Fruit Fungicide Efficacy Table. Their older table rated it as "Good". I see their new table rates it as "Fair to Good", the same as the Midwest Guide. Table 6.2.3

The next time you come across any field research about the efficacy of Captan, please shoot it my way. I'd be interested in reading it.

Olpea, I don't understand how the height of the tree could be a factor but maybe it is due to greater shade and tougher rot issues.

I agree that resistance is a big concern and if captan is working for you then there may be no reason to use something else. I'm using even less effective sprays than captan and am not all that unhappy - I just add some sulphur/serenade or oil/serenade to every tank mix.

I looked for articles earlier this morning and could not find ones I had found before. I did find one below (abstract anyway). One thing I really dislike about the ag researchers is you have to pay $$ to get the full articles. Govts pay for the research so it should be free.

Scott

Here is a link that might be useful: brown rot article

Thanks Scott.

"Olpea, I don't understand how the height of the tree could be a factor but maybe it is due to greater shade and tougher rot issues."

One of the major criteria for EPA labeling is the concentration of the compound over a given land area. This works well for environmental concerns (water quality, etc.). However, as you know taller trees take more spray per land area than smaller trees.

It's a mathematical issue. Take a tree 5' tall with a 2.5' radius. It occupies 19.6 sq.ft. and the volume of the canopy is 98 cu.ft. (For ease of illustration, I assumed the canopy is a perfect cylinder from the ground up. Obviously fruit trees don't grow quite like that, but the mathematical principle still holds.)

Next take a tree that is 15' tall with a 7.5' radius. That tree occupies 176.6 sq.ft. but the volume of the canopy is 2649 cu.ft.

From a land area standpoint, the larger tree occupies 9 times the land area as the smaller tree and would justify 9 times the amount of a given crop protectant from the label. However, from a tree canopy standpoint (volume of canopy) the larger tree is 27 times larger, so the pesticide on the larger tree can only be applied at 1/3 the strength as the smaller tree (9 times greater land area divided by 27 times greater tree volume).

Another way of saying it is that a fixed amount finished spray must be spread over a larger tree canopy, thus diluting the pesticide to the point it becomes ineffective. That's the point I think Cornell was trying to make.

Thanks Olpea, that does make sense. The overall number of leaves per acre may not be much greater with large trees (the sunlight per acre is obviously constant!) but they will be spread out over a larger volume so will be harder to cover with a fixed amount of spray. This is in fact probably a supporting reason why professional growers are going to pedestrian orchards these days, even though I never heard this angle mentioned before.

Scott

"The overall number of leaves per acre may not be much greater with large trees (the sunlight per acre is obviously constant!)"

Scott,

I'm sorry but I'm think we're missing each other. My point is there is more foliage/leaves per acre.

Think of a 5' tall tree. The length/depth of the foliage canopy is about 2' feet tall. A typical 10' tall fruit tree has a canopy about 6' tall/deep (with more leaves per given area).

Now consider a 25' tall sweet cherry. It has a very tall/deep canopy (perhaps leaves covering the top 20' of the canopy). The leaf density per land area will be much higher than a shorter tree (Leaves readily grow in less than 100% sunlight.)

Perhaps a large oak tree would be a better way to visualize the point. If it's tall enough you can stand under it during a rain storm and hardly get wet (because of the height/depth of the foliage canopy - i.e. the large number of leaves per area absorb the rain drops). You can't get away with that under a shorter (say 6' tall) tree.

Imagine trying to wet that oak tree foliage with a given amount of spray that was based on a tree with the same diameter, but only 10' tall.

This isn't just a theory. Trees with a taller/deeper foliage canopy really have more leaves per land area than trees with a shallower canopy.

Olpea, I didn't know how the raw leaf area would differ depending on height so was giving an argument not based on that -- there is simply a taller target to hit with the sprayer, and you pretty much need to hit it all.

This leaves per land area is an interesting dimension of tree growth. I just looked it up and it turns out it has a scientific name, the LAI - leaf area index, basically the area of the leaves added up divided by the land area the tree occupies. In forests it does seem like the LAI is bigger for taller trees, but its not as clear to me for commercial orchards. Since the grower wants to prune the trees to be more open the LAI may not change a whole lot in a shorter vs taller tree. I found one article comparing a 2m tall with a 3m tall peach pruning system and they both had a LAI of 5. Thats not a lot of difference in height so its hard to draw a conclusion from that. My guess is LAI on a traditional orchard will probably be a bit higher than a modern pedestrian orchard, but there will not be a huge difference.

Scott

Hey I just found some somewhat better data -- see slide 23 in the link below. It states that seedling rootstock apples have LAI of 3.8 and M9 has LAI of 4.6, which means the shorter apple trees in fact have greater LAI. I think this is a very complex question.

Scott

Here is a link that might be useful: Slides

Olpea, the grower I mentioned has scab as his primary enemy and he likes spraying in light rain to help distribute the stuff, not necessarily because it washes off and must be reapplied immediately. I agree that once it sets it's very sticky stuff- hell it's sticky even before it sets, but it only stays active for about a week as I recall. I've really never used captan as an exclusive spray but in the tank mix with SI's and sometimes a strobe. I'll go through a single jug of Captec in a season so I'm far from expert on its attributes.

As you know, one of the things Captan is touted for is it's ability to redistribute in the rain which is not quite the opposite of rain fast but is an indication that wash off will be a problem more than with a systemic which you also know.

On wet years here, it generally requires more than a single SI application to get decent stone fruit in. However, I have some sites where peaches come in without any fungicide others where a single squirt will get the crop in.

One thing I learned last year- heat is as important as humidity at causing BR. It was quite dry last year but I still had to struggle to control BR- especially on my own trees where there were peaches that were frost damaged and I didn't realize till very late that they were not getting larger than golf balls. They rotted instead of ripening no matter what chemical was on them.

Even on sites better located for frost, brown rot was surprisingly active considering how low humidity was most days. Fireblight was also, by far, the worst I've seen it. It was the closest thing to a CA summer we've had since I moved here so all of this surprised me. I'm not sure if it was the length of the growing season, which was exceptionally long or the heat, which was not all that high but very consistent.

Scott,

The problem with leaf area density is that it just measures leaves. The focus of the LAI fruit tree studies is on harvestable light. They ignore tree canopy volume (leaves and wood).

I shouldn't have said tall trees produce more leaves/area in my last post. I started out discussing canopy volume and then momentarily equated canopy volume to leaves/area, which was a mistake. They are two different things.

Obviously as a tree is larger there are less leaves in the interior, as more structural wood takes it's place. Leaf area density may well decrease, but the canopy volume per area will increase. That's the part that is relevant to spraying, since the whole canopy must be sprayed (leaves and wood).

Think of it this way. A given house has a certain footprint. An average new house probably covers something like 1000 sq.ft. of land area (living area inside the house is generally much bigger because of multiple floors.) Assume the house needs a roof. If it was a perfectly flat roof, it would require 1000 sq.ft. of shingles (or 10 square) assuming no eaves. However, if that same house had a gable roof, it would take more than 10 squares to roof it. In fact, as the pitch of the roof increased it would take more and more squares because the area of the roof would increase. With a 12-12 pitch it would take almost 50% more shingles than a flat roof. A roof with the slope of a Christmas tree would have an area more than 50% of a flat roof.

Fruit tree canopies don't grow quite like Christmas trees (although large sweet cherries can resemble that shape) but all fruit trees have vertical canopy (Generally speaking taller trees have a steeper pitch.) The larger the vertical canopy, the greater the canopy volume per area and the more spray required per area.

Hman,

I've also read how Captan redistributes to new foliage well. I've never understood how on the one hand it is known for having both good adhesion and good redistribution at the same time.