Normal coneflower (left) & deformed coneflower (right) Photo: Christy Frederick, Master Gardener.

Strange Stems

Christy of Pineville saw something unusual in her garden, “… I saw this on purple coneflower [in my garden].”

There seems to be a couple of reasons for these deformed flowers. Dr. Raj Singh, the AgCenter’s “Plant Doctor” conveyed his comments, “I have seen this problem in cone flowers and industrial hemp in Louisiana. It is call plant fasciation and may result from hormonal imbalance, genetics, or environmental responses. Exact cause of plant fasciation is not known.”

Steven Gower, Michigan State University Diagnostic Services, described this condition as “Fasciation is a term that describes the abnormal fusion and flattening of plant organs, usually stems, resulting in ribbon-like, coiled, and contorted tissue.”

The other reason for the deformed flower in the image may be “aster yellows.” The Texas Plant Disease Handbook provides some more detail, “Aster yellows is a disease caused by a mycoplasma-like organism which attacks a wide range of plants.” This range of plants include:

Crops: broccoli, buckwheat, cabbage, carrot, cauliflower, celery, endive, flax, lettuce, onion, parsley, potato, parsnip, pumpkin, red clover, salsify, spinach, strawberry, and tomato.

Flowers: aster, anemone, calendula, Centaurea, China aster, chrysanthemum, Clarkia, cockscomb, Coreopsis, cosmos, delphinium, daisies, Gaillardia, hydrangea, marigold, Nemesia, Paris daisy, periwinkle, petunia, phlox, Scabiosa, snapdragon, statice, strawflower, veronica, and zinnia.

Weeds: cinquefoil, daisy fleabane, dandelion, horseweed, plantain, ragweed, thistle, wild carrot, and wild lettuce.

A tiny insect called a “leafhopper” spreads this disease for one hundred days after its initial infection. These leafhoppers spread the disease from host weeds to garden flowers and vegetables.

Finally, The Texas Plant Disease Handbook provides these control measures for aster yellows:

(1) Obtain healthy seed, cuttings, and plants.

(2) Early control of leafhoppers on lettuce and carrots.

(3) Spray weeds surrounding field with insecticide according to current recommendations.

(4) Apply insect control before cultivation, weeding, and other field operations.

(5) Control weeds during the growing season in the field, on irrigation ditch banks and in surrounding areas.

(6) Avoid rotations where one susceptible crop follows another.

(7) Destroy volunteer overwintering plants and avoid planting near established diseased crops.

(8) Destroy affected plants in small areas as soon as they are diseased.

(9) Screen small plantings with wire mesh to exclude leafhoppers if practical.

Bumps on a tomato stem are normal. Photo: Melinda Fuller

Tomato Wilts & Bumps

Melinda sent an email about her tomatoes, “Do you have any idea what could be wrong with this tomato plant. Left for a weekend and came home to find one plant completely wilted. Use drip irrigation so was not water supply. I spray entire plant with Neem oil but finally pulled it because afraid it could have a virus and spread. I do have two other plants that have upper limbs that are starting to wilt. Notice the bumpy stem. The roots looked fine when I pulled it. Any help would be appreciated.”

There are three main causes of wilt in tomatoes:

• Southern bacterial wilt (SBW): Potatoes, eggplants and peppers would also be susceptible to SBW.
• Southern Blight: SB is a fungal disease, and like SBW, and exists in the soil.
• Tomato Spotted Wilt Virus: An insect, called a thrips, spreads this viral disease, and it also affects peppers and eggplants.

All tomato plant with wilt symptoms should be removed to prevent spread to healthy plants. The best way to avoid these diseases is prevention. Read labels to see which varieties are resistant to SBW, SB & TSWV. Also, avoid planting tomatoes, potatoes, eggplants & peppers in the same place. For TSWV, thrips avoid plants with mulch, but the reason thrips avoid mulched plants is unclear.

The bumps on the tomato stem are normal. The University of Maryland Extension website reports, “Small knobs, swellings, or bumps on stems are usually harmless and caused by plant genetics (natural growth) or stressors in the environment. Pepper, tomato, and rosemary plants often exhibit such growths. No action needs to be taken.”

A tomato infested with a fruitworm. Photo: Lori Dupre, Baton Rouge.

Tomato Fruitworm

Lori is having a tomato problem, too, “I went away for the weekend and came back to find something had moved in on one of my tomatoes. It looks like eggs of some kind and there are small holes on the side of the fruit. I intend to cut off this one tomato, but I would like to know what this is and if there is a preventive treatment to use so that other fruits are not lost.”

The “eggs” on the top of this tomato in the image is fresh “frass” or “insect poo” from a tomato fruitworm. Chemical control could include Sevin, Malathion, Bifenthrin or Permethrin. Organic control could include Spinosad, Dipel or Thuricide. As always, read the label of each insecticide for safe and effective use.