Pepper plants, including the jalapeno, have a reputation of being quick and easy to grow. While that is true, they are also susceptible to several pests and diseases that can quickly destroy an entire plant or reduce the yield of peppers. Knowing the signs of disease or infestation can help save both the plant and the peppers it will produce.
Along with many other garden vegetables and plants, jalapeno plants are especially susceptible to attacks from aphids. They can be seen on the bottom of leaves and often look like little green or white dots. A clear or white sticky film may also coat the leaves or the peppers when aphids are present.
Appearing as large black spots on the peppers, usually near the tip, blossom-end rot can have several causes. Lack of water is the most common, but it can also occur when there is not enough calcium in the soil. Once blossom-end rot sets in, it is too late to cure or correct, but noting the conditions that caused it, such as lack of water, allows it to be corrected in the next planting.
There are at least three types of leaf spot that attack jalapeno plants and, according to Texas A&M Agrilife Extension, they often are present together. Typical signs included wilted leaves, leaves with spots or plants that lose their leaves entirely. Agrilife recommends treating leaf spot with a combination spray of chlorothalanoil and a copper fungicide. Treatment must begin at the first sign of infection.
Leaf miners are not a specific pest, but the term refers to a group of pests that lay their eggs on leaves; the emerging larvae then feed on the leaves. They include moths, beetles and flies. A wavy or squiggly line on the leaf, or an unusual pattern that appears like a blister is a tell-tale sign of leaf miners. University of Florida Extension recommends using an insecticide to remove the infestation. If the infestation is mild, a plant may continue to grow and set jalapenos, but the yield will probably be reduced. Removing the affected leaves may temporarily stop a mild infestation.