You're welcome. While the original outbreak is believed to be the Bonny plants from the big box stores, it shows how dangerous Late Blight can be. If you originally bought Bonny plants, they may have been dead much sooner in the season; if they weren't Bonny plants from the nursery, and you still got it, it goes to show how easy this disease can spread.
Now multiply everything by the fact that there are still many people who don't have the internet to read these things, see these reports & pictures, etc. Many are still in the dark. They lose everything and don't do proper cleanup and contribute to the spread of the disease without even knowing it.
Luckily for us in the northern states, it's difficult for it to overwinter if we have a hard freeze. And while there are different strains, we so far only have asexual reproduction of the spores. There are actually what they call A1 & A2 lines; it's hard to understand how this works but consider one as a male and the other as a female, asexually they reproduce by themselves, but if we get both in the same place at the same time, they mate and can survive by sexual reproduction. Think of it as a "super strain" that would be hard to contain if that happens. I think this has happened in Mexico or S. America or somewhere.
Sorry, I'm not a microbiologist or anything, the best info on the A1 & A2 is in that FAQ link and the weekly update link
http://nysipm.cornell.edu/scouting/l...ht/default.asp.
Here's the most interesting stuff:
Why an endemic problem but not an epidemic catastrophe in susceptible crops this summer?
As previously documented, the spring and early summer of 2009 was setup for losses in tomato and potato crops of unprecedented proportions, given that infected tomato plants had been sold to unsuspecting home gardeners from large "big box" stores and environmental conditions (frequent rains and cool temperatures) were common throughout the NE. Additionally, in the case of potatoes, late blight occurrence in 2008 in some seed producing states, also could provide inoculum on infected tubers used for the 2009 crop. Based upon tests to identify the clonal lineages of Phytophthora infestans conducted in Dr Fry's lab at Cornell, the isolates recovered from infected tomato and subsequently infected potato did not fit any of the previous late blight genotypes previously identified in NY. The new genotype is mating type A2 (perhaps P-T, but not as virulent as some in the past), unlike the previous genotypes like US-11 (P-T) and US-17 (p by laboratory tests only-T) which are A1 mating types and were even more destructive on tomato. The pathogenicity indicated by (P-T) refers to pathogenic specialization on both crops, where capital P and T indicates primary pathogens of both crops, while a lower case letter indicates less pathogenicity for the crops. Separate infections did occur in potato in western NY and were identified as US-8 (mating type A2, P). US-8 is now the primary genotype of late blight infecting potato on a regional basis. So, our salvation this summer was that the primary genotype(s) spread throughout the region were apparently not as pathogenic on tomato and potato as we have encountered in other years. This is little consolation to homeowners and organic growers who suffered total loses, but does explain how some growers were able to keep losses to a minimum.
What steps worked for growers faced with late blight in 2009?
I will divide this discussion into two parts, since we are dealing with the two different genotypes in NYS, and the actions taken are different. In the case of the unidentified A2 type originating initial from tomato (not quite P-T, but close) that spread to tomato and potato, growers (both conventional and organic) relied upon a tight fungicide program (5-7 day schedule) with late blight specific fungicides in conventional operations (products including contact materials like chlorothalonil, Gavel, and Ranman, and translaminar materials like Curzate, Previcur Flex, Revus, and Tanos). Organic growers relied on copper fungicides applied on a 3-4 day schedule (Nu-Cop and Basic Copper 53). Another procedure followed, especially by organic growers, was to flame out of the most aggressive hot spot areas located near tree lines to remove the most heavily infected plants early in the initial spread of late blight. This practice undoubtedly saved a lot of the crop and allowed copper sprays a chance to reduce remaining infections. In organic operations we also saw growers cutting down infected potato foliage of more susceptible varieties in an effort to reduce the inoculum level in their fields.
In the case of commercial potato fields faced with the need to control US-8 (mating type A2, P) within their crop (likely originating from infected seed tubers), the steps take were more aggressive. Hot spots of infection in fields were killed as soon as detected and then an aggressive 4-5 day spray schedule was followed using the late blight specific products mentioned above.
The bottom line in both cases this season, the successfully control on late blight hinged on the application of appropriate fungicides on a very tight schedule.
What can we expect for the remainder of the season?
Unfortunately, we are not out of the woods by any means, as what I call "back filling" of infections is still occurring in remaining susceptible crops (potato and tomato) in both homeowner gardens and commercial acreages (both organic and conventional). Reports of late blight infections just now appearing in home gardens and isolated cropping areas are just now coming in. Although a brief spell of hot weather may have slowed down late blight a bit, it is still sporulating and producing inoculum during our heavy evening dew periods. All concerned interests must continue on a regular fungicide program until the crops are finished. Special care must be made in the case of potato to examine harvested tubers to make sure they are free of tuber blight. It is advisable to move the crop as soon as possible to reduce tuber infections in storage. The other significant reminder is to make sure that all tubers are harvested and that special attention is directed to removing and destroying volunteers that may survive the winter season and have the potential of carrying over late blight to next year. A common problem is encountered when corn is planted as the rotational crop in fields that had late blight this season. Volunteer potatoes are difficult to rogue out when hidden by the emerging corn or other rotational crop.
What can we learn from tomato and potato crops with more limited infections?
Differences in the amount of infection of potato and tomato, both traditional varieties and heirlooms, have been observed this year across the state. For sure there are definitely differences in the amount of infection for both crops. However, given that the predominate clonal lineage that occurred this year is apparently not as aggressive as those encountered recently, this might lead one to consider a variety as resistant or tolerant to late blight, when in fact in another year is could perform differently. One fact does remain, with the exception of comments made about overwintering of inoculum on potato tubers, next year we begin the season with a "clean slate", one that will be more kind to all fanciers of tomato and potato.
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Keep in mind that all it takes to spread into 2010 is just ONE buried potato that was infected that someone missed harvesting; P. infestans needs a live host and while the potato plant above ground may be dead, the actual potato (tuber) below ground may still be alive and harboring Late Blight! When it sprouts a plant next year, we can be reliving this all over again!
