Late Blight
- Issue type
- disease
- Seedborne
- No
- Resistance code
- LB, Ph-2, Ph-3
- Affects
- Tomato
Symptoms
Large gray-green water-soaked blotches that brown within days, white sporulation on leaf undersides in humid mornings, and firm brown greasy patches on fruit. Spreads regionally on storm fronts and can level a planting in under two weeks, the Irish famine pathogen on its second host.
Management
Because inoculum blows in, sanitation alone cannot hold it; resistant varieties carrying Ph-2 + Ph-3 (Mountain Magic, Defiant PhR, Iron Lady) changed the game for growers in blight-prone regions. Destroy volunteer potatoes and infected plants immediately, cull piles are the classic season-starting source. Regional monitoring networks track outbreaks in real time.
Varieties with documented resistance
| Variety | Level | Code | Basis | Days | Breeding |
|---|---|---|---|---|---|
| Mountain Magic | resistant | Ph-2+Ph-3 | Independently observed | 66-70 | F1 hybrid |
| Defiant PhR | resistant | Ph-2+Ph-3 | Independently observed | 65-70 | F1 hybrid |
| Iron Lady | resistant | Ph-2+Ph-3 | Independently observed | 75-80 | F1 hybrid |
| Mountain Merit | resistant | Ph-2+Ph-3 | Independently observed | 73-77 | F1 hybrid |
| Mountain Rouge | resistant | Ph-2+Ph-3 | Independently observed | 74-80 | F1 hybrid |
| Damsel | resistant | Ph-2+Ph-3 | Breeder declared | 70-75 | F1 hybrid |
| Mountain Gem | resistant | Ph-2+Ph-3 | Independently observed | 70-78 | F1 hybrid |
| Galahad | resistant | Ph-2+Ph-3 | Breeder declared | 69-75 | F1 hybrid |
| Celano | resistant | Ph-2+Ph-3 | Breeder declared | 60-65 | F1 hybrid |
| Purple Zebra | resistant | Ph-2+Ph-3 | Breeder declared | 75-80 | F1 hybrid |
| Matt's Wild Cherry | tolerant | - | Independently observed | 60-70 | open-pollinated |
| Legend | intermediate | Ph-2 | Independently observed | 68-70 | open-pollinated |
| Juliet | tolerant | - | Breeder declared | 60-62 | F1 hybrid |
| Plum Regal | intermediate | Ph-3 | Independently observed | 68-75 | F1 hybrid |
| Jasper | tolerant | - | Independently observed | 60-65 | F1 hybrid |
This is the page where the difference matters most, because it is where a variety gets chosen for its resistance. Breeder declared means the claim comes from whoever breeds or sells the seed, which for most resistance genes is the only evidence that exists. Independently observed means an institution with no stake in the sale grew the plant and reported what happened.
Trials that measured this disease
Published field evaluations where researchers grew varieties and rated this disease themselves. These are the strongest evidence on this page, because the observation and the seed have no common owner.
Evaluation of Late Blight Resistant Tomato Varieties, 2013
2013 · New York · field
| Variety | Measured | Result |
|---|---|---|
| Mountain Magic | Late Blight severity | 1.3 % |
| Mountain Magic | Late Blight: disease progress (AUDPC) | 78.3 index |
| Matt's Wild Cherry | Late Blight severity | 0 % |
| Matt's Wild Cherry | Late Blight: disease progress (AUDPC) | 26.4 index |
| Jasper | Late Blight severity | 8.6 % |
| Jasper | Late Blight: disease progress (AUDPC) | 99.3 index |
| Defiant PhR | Late Blight severity | 2.3 % |
| Defiant PhR | Late Blight: disease progress (AUDPC) | 137.2 index |
| Iron Lady | Late Blight severity | 1.6 % |
| Iron Lady | Late Blight: disease progress (AUDPC) | 125.2 index |
| Mountain Merit | Late Blight severity | 3.1 % |
| Mountain Merit | Late Blight: disease progress (AUDPC) | 220.9 index |
| Mr. Stripey | Late Blight severity | 11.9 % |
| Mr. Stripey | Late Blight: disease progress (AUDPC) | 203.6 index |
| Plum Regal | Late Blight severity | 31.3 % |
| Plum Regal | Late Blight: disease progress (AUDPC) | 894.5 index |
| Legend | Late Blight severity | 42.5 % |
| Legend | Late Blight: disease progress (AUDPC) | 728.3 index |
| New Yorker | Late Blight severity | 86 % |
| New Yorker | Late Blight: disease progress (AUDPC) | 1,285 index |
| Mountain Fresh Plus | Late Blight severity | 71.8 % |
| Mountain Fresh Plus | Late Blight: disease progress (AUDPC) | 1,058.1 index |
Evaluation of Late Blight Resistant Tomato Varieties, 2012
2012 · New York · field
| Variety | Measured | Result |
|---|---|---|
| Mountain Magic | Late Blight severity | 0.1-0.3 % |
| Matt's Wild Cherry | Late Blight severity | 0.1-0.3 % |
| Jasper | Late Blight severity | 0.1-1.8 % |
| Mountain Merit | Late Blight severity | 0.1-1.9 % |
| Defiant PhR | Late Blight severity | 0-0.2 % |
| Legend | Late Blight severity | 18.9-42.8 % |
| Plum Regal | Late Blight severity | 11.3-81.3 % |
| New Yorker | Late Blight severity | 55.6-88.8 % |
| Mountain Fresh Plus | Late Blight severity | 47.3-85 % |
| Juliet | Late Blight severity | 37.8-70 % |
Sources & References
Evidence: 1 source, an independent reference.
- Vegetable MD Online · Cornell University, Plant Pathology, University or Government