Late blight can be devastating to fruits, stems and leaves when weather conditions are favorable (long periods of muggy weather with cool nights and moderately warm days). Affected plants look as if they were killed by frost. Both green and ripe fruits become corky brown on their surfaces and develop a texture resembling that of an orange peel. The rotten areas remain firm but make the fruit inedible.
Use a preventative spray containing the disease-fighting bacterium Bacillus subtilis every 7-14 days. Start applications when you first start getting foliage. If disease persists or you notice symptoms before you can apply a preventive spray, spray a copper soap fungicide, and repeat at 7- to 10-day intervals until weather conditions are no longer favorable. If late blight is an annual problem, begin spraying at transplant time and continue through harvest. We recommend Plant Guardian™ Biofungicide Liquid Concentrate and Soap-Shield Flowable Liquid Copper Fungicide.