The Sun News

MEEKS: Plant diseases can thrive in rainy weather

The recent rains may have all of you ready to build an ark. I have never been one to complain about rain, but the weather that we have been having has been ideal for many plant diseases. Diseases need four things to establish: a host, right environmental conditions, time and the pathogen. This is known as the disease triangle, with time being in the center of it all. There are four types of organisms, pathogens, that cause plant diseases; fungi, bacteria, viruses and nematodes. Fungi and bacterial diseases usually occur when environmental conditions are warm, raining and humid. There are some diseases that occur with hot and dry conditions. Viral diseases occur when they are transferred to the plant from a host. For example, thrips are known to transfer viruses such as tomato spotted wilt. Nematodes are found in the soil and cause problem to the root system, ultimately affecting plant growth and yield. Nematodes can only be detected by pulling a soil/roots sample and sending it to the lab.

Even though there are many factors that are beyond our control, there are a few practices that can help prevent the spread of disease. For the purposes of this article I am going to focus on vegetable gardens, but much of this information can be applied to all plants. The first is site selection. Vegetable gardens need to be in a sunny, well-drained area that is well-ventilated. Crop rotation also will help reduce disease. Vegetables that are in the same family should only be grown in the same area once every three to five years. This will reduce pathogen buildup in the soil. When available, plant disease-resistant varieties. When saving seeds, only save seed from healthy plants and consult seed saving guidelines for which seeds can be saved. Plant seed base on soil temperature and not time of year. If the soil temperature is too cool or warm it can effect seed germination and increase the chance of seed borne diseases. Adjust planting dates to avoid when pest pressure is at the highest. Proper spacing of plant will help increase ventilation reducing foliar disease, allowing the leaves to dry more quickly.

Vegetables need an inch of water a week. Too much and too little soil moisture can increase the chance of diseases. Mulching will help keep pathogens from splashing back from the soil onto the plant when it rains. Proper fertilization and pH also will help with decreasing plant disease. This can be determined with a soil test. Weeds compete and harbor insects and should be controlled to reduce diseases. Sanitation, which is the removal of diseased plant material, will reduce the chance of future disease outbreaks. Fungicides should be used as a last defense. Fungicides will keep it from spreading but will not cure the areas that are already infected. They should be as a preventive, when the conditions are favorable for the disease.

Following these management practices can help reduce plant disease in your garden.

Source: UGA Publication, Elizabeth Little, Disease Management in the home Vegetable Garden


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