What is Blight?
Blossom end rot (BER) is a disease caused by the fungus Phytophthora infestans. The bacteria Bacillus thuringiensis var. novyi is responsible for causing BER. Bacteria are normally present in soil and water but they multiply rapidly when there are poor aeration or moisture conditions such as those found during severe drought or hot weather. They thrive in these conditions because they have a high metabolic rate. When the temperature rises above 95 degrees F (35 C), the bacteria begin to die off. The spores then germinate and grow into new forms called “cysts”. These cysts produce more bacteria which cause further growth until it reaches a point where the bacterial population is so great that it causes the death of healthy plants. The bacteria releases toxins that kill other plants nearby.
The bacterium produces a toxin called phytotoxin. It is very toxic to many types of plant life including tomatoes, eggplants, peppers, cucumbers and onions. If left unchecked, BER will eventually wipe out your garden if not controlled before it becomes too advanced. There are several ways to control BER:
Control weeds early in the season using herbicides or pesticides such as glyphosate (Roundup). This helps to ensure that the plants have enough water, sunlight and nutrients.
Water thoroughly to prevent drought stress. If leaves begin to wilt, give them water as soon as possible.
Mulching helps maintain soil moisture and keeps the soil cool.
Plant disease resistant varieties. There are many tomato plants bred to resist BER, although some may be more resistant than others. There are also pepper and eggplant varieties specifically bred to resist the effects of BER.
Keep leaves dry. Wet leaves are more likely to become infected so make sure plants are not planted too closely and foliage is not touching the ground or other plants. Make sure that the area where you plan to grow has good air flow. Avoid overhead watering if possible.
Soak seeds in water containing 0.5 to 1% of bio-protective agent (distilled vinegar or molasses). This helps to prevent BER from occurring.
Planting marigolds in and around your garden also helps as the flowers are known to repel several types of harmful insects, including root knot nematodes.
Remove all infected plants immediately and throw them away, preferably by incinerating them.
It is important to maintain good garden hygiene by removing all plant debris after a growing season so that the spores do not over winter.
Bacteria (Bacillus thuringiensis) eat the bacterium within the root and without a food source, they die. In this case, BER will not re-occur once you apply Bt to the soil.
There are several types of Bt available such as B. thuringiensis kurstaki which is sold under the brand name “Dipel” and B. thuringiensis serovar. Each Bacillus species works in a different manner so do your research before you decide which strain to use.
Treating With Bt
Apply Bt when temperatures are above 50 degrees F and no rain is expected for at least 48 hours. This is vital as the bacteria will be killed if it gets washed away before it has time to take effect. Soil must also be moist so that the bacteria can form new spores after applying them to the soil.
How Much To Apply
The amount of Bt to apply depends on the type of plant you are treating. Use 5 to 10 milligrams per square foot of leaf area for leafy vegetables while 5 milligrams is enough for root vegetables and small seeded crops. More detailed information on how much to use can be found on the container.
Using Bt (Dipel) For Root Knot Nematode
1. Dissolve 1 tbsp of Dipel in 2 cups of water.
Stir well and allow the solution to sit for 24 hours.
2. Add 1 tsp of this mixture to each gallon of sprayer tank.
Fill with water and mix well before using.
Sources & references used in this article:
Commercial pepper production handbook by WT Kelley, GE Boyhan, KA Harrison, DM Granberry… – 2009 – esploro.libs.uga.edu
Pepper Importance and Growth (Capsicum spp.) by CMF Pinto, IC dos Santos, FF de Araujo… – … breeding of chilli peppers …, 2016 – Springer
Bell Peppers: Growing Practices and Nutritional Value by RJ Ciju – 2019 – books.google.com
Effect of some soilless culture techniques on sweet pepper growth, production, leaves chemical contents and water consumption under greenhouse conditions by SF El-Sayed, HA Hassan, SO Mahmoud – Middle East J, 2015 – academia.edu
The role of magnesium in plant disease by DM Huber, JB Jones – Plant and soil, 2013 – Springer