Midsummer Musings: Over-watering, poison ivy and tomato diseases

Published 5:00 pm Friday, July 20, 2018

We’ve approached the middle of summer. It has been hot and dry but we’ve also have had timely rains. Keep an eye out for those tomato green hornworms. Those are the guys that defoliate your tomatoes overnight. They start out small, and by morning, they’re the size of your finger. You can track them by their droppings.

Another worm to be on the lookout for are armyworms. I’ve spotted black striped armyworms munching on the tomato fruit. There is also a khaki version of these destructive pests. You can pick these guys off early in the morning when it’s cool out.

One of the dangers during hot dry spells is overwatering. If the potting soil is moist in a hanging basket or a large pot, resist the temptation to give it an extra drink. Wet roots spell phytophera root rot, which spells death to a plant. 

You want to wet the root zone without saturating the soil. When the soil is saturated, all the air space which roots need to breathe are taken up by water molecules. The plant may suffocate to death as well as it encourages root diseases.

This advice pertains to watering lawns as well. Too much irrigation will also cause root diseases. Lawns need approximately one to one and a half inches of water per week. An easy way of determining how long to leave the sprinklers on is to lay pie plates in the watering zone and time how long it takes to get 1.5 inches of water in the pie pan and then set the timer accordingly. 

Time the irrigation in the early morning so as to prevent evaporation. Seventy percent of the water may not hit the ground when watering in the heat of the day.

Poison ivy and poison sumac

We are also having a banner year on poison ivy and poison sumac. Many people are allergic to the oils that can be wiped from the leaves and stems of the plants to our skin. Burning wood that has dried vines attached can spread the oils by the smoke into our eyes and on our skin. 

Even when wearing long pants, the oil can penetrate and cause a rash above the sock line or the knee areas. Wash clothes after working outside and wear gloves to prevent transmitting the oils. Never touch your face when working outside. Sweat can also move the oils around. Those large hairy vines growing on old trees may be poison ivy or poison oak. Be very careful cutting those down because the sawdust can cause the rash.

Birds eating the berries spread poison ivy. Poison ivy can usually be found at the base of trees in moist, shady areas. Poison ivy plants growing in the under-story are usually topped off at knee height by deer that consider it a delectable delight. 

It will continue germinate and grow through out the summer. There are several products that are effective in controlling poison ivy and sumac. Being persistent is the key to controlling these poisonous plants. Follow all label directions.

Tomato disease

Tomatoes may also be experiencing some disease problems. When examining plants for disease problems, the lower leaves will usually show symptoms first. Warm, wet weather is usually indicative of disease problems in tomatoes. 

Septoria Leaf Spot and Early Blight usually attack the lower leaves first and both may be present at the same time. Septoria first appears as small, water-soaked spots that become circular spots about 1/8th inch in diameter. It progresses to grayish white centers. Tiny, black specks may appear at the center. These are the fruiting fungal bodies. Spores may spread by splashing rain. 

The lower leaves turn yellow, whither and fall off. Early Blight most obvious symptom is the premature loss of the lower leaves. Brown to black spots quarter inch to half inch with dark edges appears on the lower leaves. The spots merge forming a “target” appearance. The fungus may also attack the stem end of the fruit causing concentric rings and black, velvety appearance. Pick off these leaves and dispose of them in a plastic bag as they appear. 

The first step to preventing diseases is to purchase disease free transplants or seeds. Disease can be spread from contaminated seeds and plants. Don’t save the seeds from last year especially if you’ve had disease issues.  

Bob Westerfield, vegetable specialist with UGA-Griffin, recommends selecting resistant tomato varieties. When you purchase seed or plants, the label has a code on it using abbreviations. “V” stands for Verticulum Wilt. “TSW” indicates resistance to Tomato Spotted Wilt. So check out the label. 

There are cultural practices as well. Plant your tomatoes in sunny locations in well-drained soil with a pH at least 6.2. Lime to the correct pH.  Fertilize according to soil test recommendation. Mulch the plants to maintain an even moisture level. Use pine bark, pine straw, newspapers and or compost. Synthetic weed barriers are also effective. 

Rotate the area where you grow tomatoes from year to year. Pathogens can build up in the soil. Remove and dispose properly the diseased plants. Don’t water the foliage. Water the base of the plant. Damp leaves encourage disease. Eliminate weeds around the garden area as well as in the garden. There are good fungicides out there if used in a timely manner. Call the office for specific recommendations.

If it’s necessary to apply insecticides in the garden or on ornamentals, make sure you do it after 7 p.m. when bees are not active. Bees and other pollinators provide an essential service in our  gardens.

What’s going on in Extension?

  • Market on Main: Every Saturday just off the square from 8 a.m. to 10 a.m. the freshest produce in Troup County.

If you have any questions or concerns, stop by or call the office. 

The Troup County Extension office is located at 144 Sam Walker Drive, LaGrange, GA. 30240 (706) 883-1675. It’s open Monday through Friday from 8 a.m. to noon and from 1 p.m. to  5 p.m.