Plant growers are alarmed if their plants have white spots on their leaves. What’s this thing? How risky is it, really? Aren’t plants going to die and crops going to be lost as a result?
There is rarely any cause for concern, but the most common source of such trouble is a disease, pests, or the consequences of poor care.
White Spots on Leaf Due to Sunburn
Small dry white spots appear on wet leaves that have been exposed to direct sunlight for an extended period.
It’s sunburn. Water droplets act like a lens, allowing light to pass through and damaging the leaf tissue.
Sunlight shining through the glass with air bubbles or other imperfections produces the same effect. A concentrated beam of light injures the leaves.
Sunburn isn’t just a problem for wet leaves. To avoid this, make sure that your plants are well-prepared before moving them outside or out of the shade.
There is a lot of ultraviolet radiation, and the delicate leaves can’t handle it. Consequently, the veins and leaf edges become white or discolored.
Diseases are often the first thing that comes to mind when gardeners notice white spots on their leaves.
It’s not out of the question that something like this could happen. Therefore, you need to pay attention to the spots and other symptoms to determine what disease affects the plant.
Dark Rims Around Light Spots
Small brown spots first appear on the leaves because of septoria, rust, and ascochytosis. Then they lighten and become dirty-white, with a dark rim around them.
Eventually, the spots spread to cover more and more of the leaves, eventually dying.
However, these aren’t the only signs and symptoms. Lesions may also appear on the stems and petioles, often brown in color. Over time, dark spots appear on septoria infected tissue.
In wet weather, a grayish coating appears on the back of the leaves of plants with rust and cercosporosis. Rust spots often crumble in the center, and holes form in their place.
Ascochytosis causes light spots with a darker border to appear in some crops.
Powdery mildew is most likely the culprit if your plant appears to be covered in a fine white powdery layer.
In the beginning, the spots are pretty small, but as time goes on, they grow in size and take over more and more space.
Plants’ leaves, stems, and even fruits are all susceptible to the disease’s ravaging effects:
- The coating is more concentrated on the leaf’s upper surface despite coating on both sides.
- Later on, it gets a little darker and thicker.
- Infected leaves turn yellow and dry out.
The Mosaic Coloration of The Leaf
White spots may alternate with regular, green areas more or less evenly. When the white mosaic virus appears in cucumbers, it causes this effect.
Young leaves often show the first signs of this disease, usually along the veins. At first, tiny spots with a yellowish or greenish cast appear.
After that, the entire leaf turns a greenish-white or yellowish color as they spread and merge.
Light green and yellow spots may coexist with white spots because this disease frequently occurs concurrently with the green mosaic virus.
Peas infected with the deforming mosaic virus have oblong spots on the veins of the leaves.
In the beginning, they are yellowish, but they turn white and eventually become nearly transparent as they age. These light green areas appear between the veins from time to time.
White Spots that are Convex in Shape
This is also known as crucifer white rust. It is harmful to cabbage, radish, mustard, and rutabaga.
Leaf, stem, and inflorescences show numerous white bumps ranging from 1-2 mm in diameter, much like blisters.
There is a noticeable yellowish tinge to the upper portion of the leaf plate where they are concentrated.
A white powdery substance comes out of the damage when broken up these growths. It’s the fungus’ spores you’re looking at.
Infested plants appear to be covered in a thick white coating. Affected areas swell and wither.
Insects that feed on tissue and leaf sap can cause white spots.
Small light dots appear on the leaves as puncture marks, then discolored spots form in these areas.
First on the leaf’s underside, then on its upper side, a delicate white cobweb appears on the leaves. It can entangle the entire plant if left unchecked.
Eventually, the spots become so numerous that they blend together, and the leaves turn yellow, wither, and dry out as a consequence.
The mites themselves are pale in color and extremely small, measuring only 0.5 mm long.
Greenhouse or tobacco thrips can cause whitish or yellowish spots on plants. With wings and a yellow-to-brown body, they are medium-sized insects that can measure up to 1.5 inches (3.8 cm).
Because they suck the sap out of the leaves, causing holes and discolored spots to appear on the leaves. More and more of them appear, and eventually, the leaf turns brown and dies out.
Insects develop in the leaves, stems, or flowers of living plants, either as larvae or adults.
Leaf miners cause white spots or pathways by drilling the leaf surface. You can quickly identify leaf miner damage by looking at the damage pattern.
At times, insects or traces of their activity may be visible on the leaf’s surface. The onion miner of the miner fly family is an example of a pest like this.
White spots can also be the result of nutritional deficiency. This happens when there is an iron, calcium, magnesium, copper, or manganese deficiency.
Iron. The tissue between the veins in young leaves turns white, yellowish, or light green over time. The veins themselves lighten as a result of severe starvation.
Calcium: An apical bud and young leaves with white apical buds often bent down and edged up.
Magnesium: The lower leaves are the first to show symptoms. A “herringbone” pattern is created when the veins’ edges and spaces between them change color.
There is no guarantee that the color will turn white. Light green, yellowish, brownish, or reddish are all possibilities for this color.
There are numerous variables to consider here, including the type of plant, the soil, and many others.
Copper: Cucumber and grain crops have white leaf tips, while lettuce and some fruit trees are whitish. The plant’s growth slows, and its leaves begin to droop and twist.
Manganese: In young leaves, gray or yellowish-green spots appear between the veins, and the discolored tissue dies.
Minerals Accumulate Due to Watering with Hard Water
White specks can be seen on the foliage despite sprinkling the leaves with hard water. However, because it’s only on the surface, it won’t harm the plant, and you can easily remove it.
But suppose they are watered for an extended period. In that case, the soil will accumulate a surplus of minerals, negatively impacting the plants. If you can, use rainwater or filtered water to water your plants.
The Unique Characteristics of Particular Varieties
Some pumpkins, zucchinis, Pattypan squash, and other plants have mottled leaves. The white spots on them are made of particular loose tissue (aerenchyma) that shields the plants from the sun’s rays.
Occasionally, it is mistaken for powdery mildew. In contrast, while these white spots are plaque in the disease, aerenchyma is considered an integral part of the leaf lamina.
Therefore, it may take a few weeks, or even months, for it to show up.
There is a slew of reasons why white spots might appear. Sunburn, various diseases, pests, or a deficiency of nutrients can all cause it.
To make an accurate diagnosis, you must consider the nature of the spots, the accompanying symptoms, and the environmental conditions in which the plant is located.