Detailed Explanation of Common Guava Diseases and Control Methods

Guava is a fruit tree that grows in tropical and subtropical regions, and is one of the better-known subtropical fruits. Guava has strong adaptability to the environment, especially having no particular requirements for soil, and is very easy to cultivate. However, being easy to grow does not mean it is easy to get a high yield; it also encounters many pests and diseases during cultivation, so the prevention and control of guava pests and diseases is very important. Below I will talk with you about the common pests and diseases of guava.

1. Guava leaf blight

Leaf blight mainly harms guava leaves. In the early stage, brown irregular patches form on the leaves, and in the middle and late stages they gradually turn light brown, with a clear boundary between the diseased parts and the normal parts. In the later stage the entire leaf becomes infected until it withers. Leaf blight is mainly caused by fungal pathogens overwintering in diseased plant residues and soil; when the rainy season comes, they begin to reproduce and spread, invading the leaves. The orchard should be cleaned up promptly, and the diseased residues should be gathered and burned to reduce the source of infection. When the disease is found, fungicides such as chlorothalonil wettable powder can be sprayed for control, once a week for one month.

2. Guava Pseudocercospora brown spot

Pseudocercospora brown spot mainly harms guava leaves and fruit. Brown irregular patches form on the leaves, with indistinct edges, and gray mold-like growth appears on the underside of the leaves. Small black spots form on the fruit skin, the middle of the fruit becomes sunken, and the edges of the sunken area are reddish-brown. This is mainly due to the spread of Pseudocercospora from diseased trees to healthy trees, and the highest incidence occurs when humidity is excessive. When diseased leaves and fruit are found, they should be removed promptly and destroyed in a centralized manner. Prune diseased branches to reduce the chance of disease, and spray fungicides such as carbendazim wettable powder to disinfect the orchard.

3. Guava sunburn fruit disease

Sunburn fruit disease generally occurs on the sun-facing side of the fruit. At first, small water-soaked spots appear on the fruit, which then turn into brown patches that are somewhat sunken. In the later stage all the patches spread to form one large patch. This disease is not originally caused by fungal pathogens; it is mainly that the sun-facing side is first scorched by the sun, allowing pathogens to invade. It mainly occurs in the high-temperature season of July and August in summer, when pathogens lurking in diseased residues and soil invade the scorched fruit and cause the disease. Remove diseased residues from the orchard, protect fruit exposed to the sun, and disinfect the orchard to reduce the source of infection.

4. Guava root-knot nematode disease

Root-knot nematode disease is mainly caused by the larvae of root-knot nematodes invading the roots of guava trees, causing the root tips to bend and gradually swell into an oval shape, with fewer fibrous roots, so they cannot normally absorb and transport nutrients. For control methods, an area with fertile soil and no root-knot nematodes can be chosen to establish the orchard, disease-resistant varieties can be selected, and the soil can be improved to reduce the presence of root-knot nematodes.

For varieties without disease resistance, diseases are relatively easy to occur. Observe the changes in guava trees carefully every day, and if any abnormality is found, immediately identify the type of disease so that the right remedy can be applied in time. In daily management, preventive measures should still be taken well. Diseases are extremely harmful to crops and can cause severe yield reduction or even total crop failure.