Question: What is wrong with my raspberry bushes? Some of the leaves have turned dark green and curled. They bloom and produce berries, but the berries never fully develop. At first, only one or two were like this, but every season more are affected.
Answer: This sounds like leaf curl, a virus disease that causes plants to be stunted and bushy with tightly curled leaves. Control by destroying all affected plants. They will not recover.
Set out certified disease-free plants in a new location as far away from the old bed as possible. Control aphids that transmit raspberry viruses using a multipurpose fruit spray containing malathion.
Question: Several of my ferns show peculiar red-brown to black bands on the leaves. The hands are narrow and extend from the center to the margin of the leaf. What is this?
Answer: Leaf nematodes. Control by burning infested leaves. Indoors, keep water off the foliage. Birdsnest and similar ferns may be treated by immersing the plants in hot water, held at exactly 110° degrees Fahrenheit, for 10 to 15 minutes. Isolate your healthy or treated ferns from those infested.
Question. What causes rhubarb leaves to turn yellow and wilt? There are no insects on the leaves. I transplanted the sick plant to new ground and broke up the root into a dozen new settings, all growing well until they reached a certain size and then wilted.
Answer: Rhubarb has several fairly common root and crown rots which produce such symptoms. The control is to plant healthy roots from disease-free fields in clean, well-drained soil. If you suspect the soil, treat it with formaldehyde, Vapam, and V.P.M.
Use Soil Fumigant or something similar before planting. Follow the manufacturer’s directions. Spray crowns early in spring and again after harvest with fixed copper or Bordeaux mixture.
Dig up and destroy infected plants and remove 6″ inches of the surrounding soil. Avoid wet mulch. Only plant rhubarb back in the old location for five or six years after first sterilizing the soil.
Question. For the past two springs, my large pyracantha bush has been covered with white flowers. When the berries form, they are blighted with dark coloring. Please tell me what and when to apply whatever is needed.
Answer: Scab causes berries to turn black, scabby, and distorted. A velvety olive-green or black mold and spots with fuzzy margins appear on the leaves. Later the leaves turn yellow and brown and drop early. Laland firethorn is quite susceptible.
Control by spraying about five times ten days apart (or just before rainy periods). Use a multipurpose fruit spray containing captan, zineb, verbal, or disclose. Start spraying just before the blossoms open. Yunnan firethorn is resistant.
Question: When my cucumber fruits grow to pickle size, they get a brown spot, and sap oozes out, forming a brown scab. Sonic tells us the disease is in the soil. I have been told it is a cue of her scab. Can you give me sonic information or suggestions to overcome this?
Answer: You have good informants! Scab is general in tourist areas. It attacks muskmelon, watermelon, summer squash, pumpkin, gherkin, and cucumber. Control by planting a disease-free seed in well-drained soil and following a crop rotation of two years or more.
Burn all plant debris after harvest. If you suspect your seed, treat it for five minutes in a 1 to 1,000 mercuric chloride solution (one 7.5 to 8-grain tablet in a pint of water). Use a glass or enamel container, for mercury eats away at metals.
The solution should be at room temperature. After treatment, wash the seed for five minutes in running water, then dust with captan, thiram, chloranil, or Seeman. In the garden, apply a spray containing captan, zineb, thiram, or maneb at seven- to 14-day intervals, starting when the vines start to run.
Cover all plant surfaces above the ground. Cucumber varieties tolerant to scab include: `Ashe.”Dark Green Slicer, “Fletcher, “Hybrid Long Green, “Hycrop Hybrid Pickling,’ and ‘Improved Highmoor.’
Question: All of a sudden, my peonies started to dry up, especially the stems with the hods and hods. What disease is this, when should I spray them, and what with?
Answer: The question of why peonies don’t bloom comes up every spring. If buds reach the size of peas and fail to develop further, the cause could be one or more of the following:
- Infertile soil (especially if the potassium level is low).
- Damage by thrips.
- Late spring frost or dry periods before bloom.
- Severe root-knot infection.
- Too deep planting.
- Excessive shade.
If you eliminate these possibilities, then gray mold or botrytis blight may be the cause, especially since you state that the stems are also dying. Control by cutting and burning the tops at or below ground level in the fall.
Spray crowns and soil 6” inches around as the shoots emerge. Use captan, zineb, verbal, or many, plus a spreader sticker or detergent to ensure thorough wetting.
Repeat 10, 20, and 30 days later. Apply the last spray as the flowers start to open. More sprays may be needed later if the weather is rainy or humid.
Question: What does a 2,4-D injury look like? I have damaged my zinnias, roses, marigolds, sweet william, and other plants.
Answer: 2,4-D injury symptoms vary depending on the concentration of the spray fumes or drift reaching your plants. Leaves and stems may be deformed, even severely twisted or curled.
Leaves usually have many sawtooth edges and close yellow veins. Leaves are often distorted, narrow, fan-shaped, and stiff. Symptoms may appear from a few days to a couple of weeks or more after exposure. Fumes or spray may drift up to a mile or more! Control by using only the amine form of 2,4-D.
Use the 2,4-D at low pressure and when the wind is away from grape, rose, tomato, zinnia, and other susceptible plantings. Use a separate sprayer for applying weed killers.
44659 by Dr. Malcolm C. Shurtleff