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There are a few different reasons for your pepper leaves turning white. The most common are:
- Powdery mildew
- Too much or too little water
- Nutrient imbalance
- White mold
- Rapid temperature changes
Let’s take a closer look at each of these common issues for pepper plant leaves. We’ll cover what to look for, how to avoid the issue, and, where possible, how to fix it.
Remember, pepper plants are fairly delicate warm weather vegetable plants. Yes, peppers are easy to grow with a little know-how, but they’re also prone to a number of pests, problems, and diseases. Aside from knowing how to successfully companion plant peppers, the best way to limit the risk of pests and diseases is to keep your pepper plants as healthy as possible. Grow them in well-nourished soil and with plenty of sun, as they’re nutrient-loving, photophilous plants.
Powdery Mildew
Powdery mildew on peppers starts as fluffy white spots, particularly on the underside of pepper plant leaves. In spite of a lot of misinformation on the internet, powdery mildew does not spread to the fruit or the entire plant, as described by British Columbia’s Ministry of Agriculture, Food, and Fisheries. Instead, if left unchecked, it ravishes the leaves, turning the underside white-gray and, as the disease progresses, brown. As the disease takes hold, the leaves are overcome and fall from the plant. Eventually, when enough leaves die off, the plant dies, as it can no longer photosynthesize.
Powdery mildew doesn’t just attack pepper plants. And it’s highly contagious. Even gentle air movement can carry the mildew spores onto nearby plants, where the infection rapidly spreads.
Can You Prevent Powdery Mildew on Peppers?
While you can’t guarantee prevention, there are steps you can take to significantly reduce the risk. Choosing the right pepper varieties helps, as some are more resistant to powdery mildew than others.
Also remember to give the plants plenty of space. Powdery mildew, like many fungal pathogens, thrives in warm, damp conditions, so make sure you minimize weed growth and leave enough space between plants to allow good airflow.
Another trick is to not plant peppers in soil where you know powdery mildew has been present in the last 8 years or so. And, wherever you plant your peppers, prune them, particularly at the bottom, to limit fungal spores splashing up from the soil onto the leaves.
Lastly, use a drip irrigation system, or water gently at ground level. Never splash water from a sprinkler or hose from above, as water drops hit the soil, gather soil particles and pathogens, and then bounce back up onto your pepper plant leaves.
Can You Fix Powdery Mildew on Peppers?
While there are fungicidal products available, we grow organically, so we wouldn’t recommend them. However, some people have found success with some natural remedies, including using a spray of one part milk to nine parts water on affected plants. Some studies and lots of anecdotal evidence suggest this remedy is more successful than most commercial fungicides.
You can also use a spray made of a tablespoon of baking soda, 5 tablespoons of horticultural oil, and one gallon of water.
I’ve had success with using milk but have never tried the banking soda. I do, however, have experience with a garlic spray to combat powdery mildew. Basically, you crush or puree two whole garlic bulbs, then squeeze out the juice by straining through a fine mesh seive or a cheesecloth, then discard the pulp. Now, to the garlic juice, add a few drops of Dawn dish soap, and store the extract in a tightly sealed jar in the fridge. When you’re ready to use it, add one part garlic juice to ten parts water in a spray bottle and coat affected plants.
Too Much or Too Little Water
Pepper plants are fussy when it comes to moisture. Too much or too little, and they’ll get all kinds of problems. One of the key ones being lightening or whitening of the leaves. Water pepper plants with tepid water early morning or late evening, before or after the heat of the day. This prevents the water evaporating in the heat or sitting on the leaves and causing burns.
Young plants, in particular, should be watered with extra care. Pepper seedlings are very delicate and watering them with water that’s too cold shocks them so that they cannot absorb enough nutrients. To compensate, the new growth at the top of the plant pulls vital nutrients from the bottommost growth, which then starts to pale and whiten.
And remember to let the soil dry out between watering. Peppers loathe having perpetually wet “feet”. They like having a regular, gentle drink of warm water, but they don’t like the soil to stay wet and soggy.
Nutrient Deficiencies That Cause Pepper Plant Leaves to Turn White
A missing nutrient is often the culprit when your pepper plants start to show white patches on their leaves.
The three key nutrients that are often deficient in soil and can cause whitening are iron, nitrogen, and copper. While magnesium is the most common deficient secondary nutrient, that causes pepper plant leaves to turn yellow, not white.
Unless your soil is lacking in all nutrients, it’s unwise to just apply whatever general-purpose fertilizer you have to hand. You can see the common symptoms of each nutrient deficiency below, but a great way to see what amendments you need to make is to purchase a comprehensive soil test like this one which can tell you which nutrients are lacking, or what you have too much of.
Iron
If your soil is lacking in iron, you’ll notice young leaves at the bottom of the pepper plant start to turn white. To amend the soil naturally, apply blood meal fertilizer, like this good-value offering from Burpee, or chelated iron, like Grow More’s concentrated tub.
Nitrogen
If nitrogen is the culprit, you’ll see white patches forming on leaves anywhere on the plant, not just confined to the top or bottom. To fix nitrogen deficiency in pepper plants naturally, use blood meal, as with iron deficiency. You can also use crab meal, feather meal, fish meal, well-rotted manure, or neem seed meal. And, of course, you can use your own compost.
Copper
If your pepper plants are deficient in copper, you’ll see the tips of the leaves turning white, and they’ll curl toward the middle, too. You need either a high-quality micro-nutrient fertilizer or something like Opulent Copper that can be used as a soil amendment or a foliar spray.
White Mold
If you spot white mold on a pepper plant, you’re in trouble! If you don’t act fast and remove the infected plants, white mold can sweep through an entire pepper plant crop in days. You’ll first see white spots or patches on the bottom pepper plant leaves and stems, closest to the root zone. And you’ll see soft, pale or white lesions that are sometimes wet. As the disease advances, large black sclerotia (fungal bodies) appear in the lesions.
Just like powdery mildew, white mold, or sclerotinia sclerotiorum, thrives in damp, humid areas, so open growth, properly spaced plants, and plenty of airflow is critical in trying to mitigate the risk of this infection. The same watering and care strategies should be employed, too.
If your pepper plants do get white mold, there’s not a huge amount you can do about it using natural methods. In the very early stages, you may be able to save diseased plants by removing any infected leaves and keeping a close eye on the plant to see if more lesions appear. The best course of action, though, if the disease is already progressing, is to remove the infected plants as soon as possible and dispose of them (whatever you do, don’t compost infected plants!).
As the disease progresses, the pepper leaves get swamped with spores, and the disease progresses to the stems and pepper pods, too, eventually ruining the fruit and killing off the entire plant.
Rapid Temperature Changes
Your pepper plants are delicate, particularly while they’re young. And they love warm weather. As a warm weather vegetable, pepper plants struggle to adapt to cold conditions and most definitely don’t cope well with rapid temperature changes.
Pepper plants can’t tolerate freezing temperatures and they can’t cope with a sudden drop from warm to cold with no hardening off period. So, failing to harden of your pepper plants before moving them out of the greenhouse to their final position or having a sudden, unexpected cold snap and failing to protect the plants from frost will result in white leaves turning to brown or drooping before falling off.
Sudden hot weather with too much direct sunlight can cause problems, too, including sun scald, which can make pepper leaves turn white and can also burn the pepper pods.
When growing peppers, you need to think about the outdoor growing environment and leave plenty of space for airflow to make the area inhospitable for any common fungal disease, but you should also think about light. Pepper plants need plenty of direct sun, but they should have a little dappled shade for at least part of the day, too. Particularly while they’re being hardened off, or acclimated to the outdoors.