What is Angular Leaf Spot
This is a leaf disease that results from pseudomonas syringae pv. Lachrymans. It is caused by bacteria that is host-specific, which primarily targets plants that belong to the family of cucurbits. Its symptoms will start out as small, but they can quickly escalate into a bigger problem when you do not treat them. Excessive moisture and ambient temperatures are some of the external factors that can contribute to the worsening of this leaf disease. The longer the leaves are left exposed to wetness from the rain, the higher is the likelihood that it will suffer from this problem. Heavy dews and overhead irrigation will also most likely contribute to the problem.
Angular leaf spot is a seed-borne disease. The contamination in the seed is the start of the disease as it affects the plant in its growth. Transfer from one plant to another can occur through a number of means, such as through air, insects, farm equipment, and spreading through the hands of farmers or gardeners. Spreading becomes easier if the plant is wet from rain or dew. Soil that is blown by the wind is also another culprit for the spread of contamination. This bacterium is also capable of overwintering in the crop and will stay there for up to two and a half years.
Identifying Angular Leaf Spot’s Damage
As a host-specific disease, angular leaf spot infests only those plants that belong to the family of cucurbits. To be specific, its common hosts include cucumber, melon, zucchini, pumpkin, cantaloupe, summer squash, and strawberry plants.
The following are some of the most common indications that angular leaf spot is affecting your plants:
- There will be small and angular holes on the surface of the leaves. Through time, they will grow larger, which also means that the disease is getting worse by the day. It starts on the underside of the leaf, but once the holes enlarge, they will be visible even on the upper surface of the leaf.
- Aside from the holes, the leaves will also show discoloration. The leaves will dry, and eventually, they will become yellow, black, brown, or gray. These are all signs that it is no longer healthy and that it will not take long before effects of the disease will become apparent on the other parts of the plant as well.
- The fruit will also show signs of angular leaf spot. There is usually a yellow halo around the hole. The hole will make the fruit susceptible to the entry of pathogen and hence, it will suffer from soft rot. Some parts of the fruit will be softer than the other, even if it is not yet ripe.
Results of Infestation
As this is a leaf disease, the damage will be mostly cosmetic, as shown by the unattractive appearance of the leaves of its host. It inhibits photosynthetic activity and the transfer of the nutrients that the plant needs for its healthy growth. This can lead to discoloration, wilting, and eventually, the plant will die. If the infestation is severe, it is not uncommon for commercial growers to suffer from economic loss as a result of damage to their crops.
How to Get Rid of Angular Leaf Spots
Natural and Organic Solutions
To get rid of angular leaf spot in a manner that is safe and effective, below are some of the solutions that hold a lot of promise:
- Among others, one of the best things to do is to plant varieties that are resistant to the disease. For strawberry, there are no varieties that can resist angular leaf spot. For cucumbers, on the other hand, there are some cultivars that will resist the disease.
- Watch out for the early signs of the disease. If you are sure that angular leaf spot is affecting your plants, pull it out right away. Leaving the plant on the ground will make it easy for the disease to spread even to healthy plants. For this reason, crop rotation will also be a big help.
- Proper spacing of plants will also help. This will encourage air circulation so that the leaves will easily dry and will be free from infection. To add, if plants are far from each other, the disease will not easily spread.
- Another primary control is using seeds that are free from pathogens causing angular leaf spot. This disease starts from an infection in the seed, which is why it is important to choose your seeds wisely. It will help to soak the seeds for 20 minutes in water with acidic cupric acetate or tartaric acid. The temperature of the water should be about 50 degrees Celsius. This will help in the elimination of bacteria from the seed, although not a guarantee.
- Irrigation systems also need your attention. Avoid overhead irrigation systems. Drip irrigation is a better choice. Also, see to it that there is proper drainage. If not, water will remain stagnant on the surface. This will make the soil moist and will encourage the growth of pathogens that carry angular leaf spot. Practice good watering.
- Especially in large plantations, tilling or mowing the soil will also help. Do this before planting the next season. This will provide the assurance that the soil is healthy. Remove plants from the previous season, especially is some of them showed signs of angular leaf spot.
Chemicals are not the best ways to treat angular leaf spot, but they can also be promising in terms of their effectiveness. There are few chemicals that will work for this disease. Among others, one that can be effective is a bactericide with copper. Copper sprays will be instrumental in the prevention of the disease and the reduction of the extent of the damage. Bonide is one of the examples of a liquid copper spray. Application should be done during the dormant season to enjoy a high level of effectiveness. However, keep in mind that it is important to observe caution. It contains toxic ingredients that can cause skin irritation and itching, among other problems.