Tomato disease update

Update on bacterial disease, root pathogens, late blight

Bacterial disease:

Bacterial disease is breaking out in many fields, especially where intense rain storms have moved through.  Once you see a lot of symptoms, there’s not much that can be done to manage it.  The disease pressure is too high for us to be able to control it.

For fields with bacterial disease that are being overhead irrigated, try to time the irrigation so the foliage will dry as quickly as possible.  I realize that this may not be possible, as it’s often a 24 hour job to get across the acres you need to cover in hot, dry weather.

Sometimes growers may add some extra nitrogen to the crop to help the crop grow new foliage.  However, the plant uses resources to produce this new foliage – resources that would otherwise go to the fruit.  If bacterial pressure is high and the new growth is quickly attacked, I’m not sure the photosynthesis contributed by the new growth will make up for the resources the plant used for the regrowth.  Nitrogen often delays the crop, too.

Root pathogens:

It is also a good time of the season to dig up a few plants to look at the roots.  The corky root pathogens can cause brown corky lesions on roots and nematodes can also cause root symptoms.  In some cases, the foliage still looks healthy, but you may be losing some yield potential.  It’s important to know what’s going on beneath the soil surface.

Late blight:

Although one incidence of late blight was confirmed in Essex County recently, since then the weather has warmed up to the point that the disease should not be active.  There have been no further confirmations of the disease in Southwestern Ontario, but keep up the crop scouting.  Once the weather cools off, if we start getting rains, fog, or dew, any late blight spores that blow in to the area will have a chance to infect.