Disease prevention in the garden

This week we explore some ways to prevent diseases in our vegetable gardens and landscapes. 

Some form of plant disease will inevitably affect your garden and flower bed, whether it be leaf spot, root or stem rot, or a host of others. Sooner or later, plant disease will enter your garden. You can bet on that. However, there are ways to reduce diseases in your garden and in some cases, even prevent them. Read on. 

Plant diseases can be caused by bacteria, fungi or viruses. All can enter your garden in a number of different ways.  And many times, it can be difficult to diagnose what the disease might be, if it is a disease at all.  In gardens, there are certain situations that are beyond our control when it comes to the incidence of plant diseases.  However, there are more ways than you may realize to prevent or at least reduce the chance of diseases affecting your plants.

One way is to create the best growing environment possible for your plants.  Keeping plants healthy is your plants’ best defense against diseases.  This includes putting the right plants in the right place.  The soil should be loose and loamy, without an excess of sand or clay, and well amended with plenty of organic matter. 

Just as location is the key to success in real estate, sanitation is the key to a healthy garden.  Start by not introducing any diseased plants into your garden.  Do this by inspecting all plants you are thinking of buying to be sure you don’t see any obvious signs, such as leaf spots, stem rots, or root damage. Next, buy plants that are resistant to various diseases, as with hybrid tomato plants. Look for varieties with at least a “VFN” on the label. 

Always keep your garden as free of weeds as possible.  Besides the obvious fact of being unsightly, weeds provide a haven for certain insect pests, which often are disease carriers.  Once they begin feeding on other plants in your garden, they can spread disease to them as well.  

People and tools commonly spread diseases from plant to plant.  Keep tools like pruners disinfected.  A solution of 1 part bleach with 9 parts water is simple and effective. Spray your tools often, especially pruners, and always after making a cut to a diseased plant.  

Mulch your plants whenever possible. Mulch provides several benefits.  One is to provide a protective barrier between the soil and foliage.  Many plants, such as tomatoes, fall victim to soil born diseases caused when water splashes up from the soil onto the foliage.    

When it comes to watering there are a few important rules to remember. Water early in the day if possible.  This gives the foliage a chance to dry out by midday.  The longer foliage stays wet, the greater the chances of disease taking hold.  The use of drip irrigation is the best way to minimize the risk of water transferring disease onto your plants from the soil.  

Leave plenty of distance between the rows in your garden.  This will allow good air circulation.  If one row is allowed to grow right into the next, the plants will never have a chance to dry out properly after a rain or irrigation.  Constant moisture above ground level encourages diseases.

Place your garden in the sunniest spot possible. Ultraviolet rays kill many would-be harmful organisms, and keeping your garden on the dry side between waterings discourages many potentially harmful organisms.

Try to avoid cultivating, pulling weeds, or thinning when the plants are still wet.  Disease organisms (bacteria, fungi, and viruses) cling to your clothes, hands, and tools, and these can easily be transferred to the plants when they are damp.  

Keep insects under control, since they are disease carriers. Do this by not allowing the area around the garden to grow up in weeds.  I realize that this is easier said than done, especially this time of year when the weeds and grass seem to display a growth spurt. Check your plants often – everyday if possible – for signs of insect damage and presence.

A prime example of this is the spotted wilt virus that we all deal with on our tomatoes. This virus is actually carried by thrips, insects which typically damage small grain crops and then move on to other host plants.

Till under or compost all plant residues after your plants have stopped bearing fruit.  Leaving them to wither untouched only provides a place for pathogenic organisms to multiply.

A word of caution is in order here, however.  Till under only healthy, unaffected plants.  The pathogens on diseased plants which are tilled under the soil will many times, under the right conditions, multiply and or overwinter in the soil and come back to haunt you in the spring.

Avoid watering your garden on muggy, overcast days.  Watering sometimes splashes disease spores present on plant leaves and on the soil onto other plants’ leaves. In other words, don’t water when the garden doesn’t need watering!

In spite of our best efforts, gardens will still get diseases.  There is no way to prevent them all.  However, if you’ll apply the above practices, you will greatly reduce the number of problems you’ll encounter. I hope these pointers will be helpful to you as you strive to produce a healthy, fruitful garden.

Tim Lewis is a Georgia Green Industry Association Certified Plant Professional, gardening writer, and former Perry High School horticulture instructor. He can be reached at (478)954-1507 or timlewis1@windstream.net.