Reducing environmental stress that causes leaf curl can help the problem and prevent it too. Start with good watering practices. Aim to provide tomato plants with 1 inch of water a week. If plants don't receive that amount from rainfall, supplement by delivering water directly to the root zone with a hose or drip line.
Once infected with the virus, there are no treatments against the infection. Control the whitefly population to avoid the infection with the virus. Insecticides of the family of the pyrethroids used as soil drenches or spray during the seedling stage can reduce the population of whiteflies.
Leaf curl is more likely to be a sign of overwatering than underwatering. (Underwatered tomatoes look droopy.) Are you checking to see if the soil feels dry an inch or two below the surface before watering?
Leaf curl can usually be controlled satisfactorily by a spray of a suitable registered fungicide at any stage of dormancy. Most effective control is achieved by spraying when the buds are swelling but before they have opened. It's not possible to control the fungus once it's entered the leaf.
Leaf curl disease shows up in spring, does the damage, and then disappears (until next spring). If your trees were infected last spring, they should have completely recovered by mid to late summer. They usually grow lots of healthy new leaves (like the photo below).
Leaf curl starts appearing in early spring on stone fruit trees. Spray a mixture of apple cider vinegar and water in winter and early spring when buds appear, then every couple of weeks. This will help with brown rot, black spot and leaf curl, to name a few.
Leaf Curl, prevention is the only way to deal with it that I know of. I start spraying my trees with Neem oil / Bonide Copper Fungicide mixture when dormant 3 times last spray when the buds start swelling but are still gray colored. Blossom Blight is a problem too, this spray takes care of that too.
Viro Raze is a powerful, versatile, and modern bio viricide that is highly effective against a broad range of plant viruses, including Chilli Leaf Curl Virus, Tomato Leaf Curl Virus, Papaya Ring Spot Virus, Yellow Vein Mosaic Virus Of Okra, Little Leaf Of Brinjal, and other viruses commonly found in crops.
Water correctly: Do not overwater. The first week tomato plants are in the ground, they need water every day, but back off watering after the first week, slowly weaning the plants down to 1 to 1.5 inches of water per week.
Tomato leaf curl disease is caused by viruses in the Geminivirus family of plant viruses, and is spread by whiteflies. The virus causing this disease is tomato yellow leaf curl virus (TYLCV).
During the Growing Season
Avoid planting new fields near older fields (especially those with TYLCV-infected plants). Manage WHITEFLIES. Cover plants with floating row covers of fine mesh (Agryl or Agribon) to protect from whitefly infestations. Rogue diseased plants when incidence of virus infection is low.
Symptoms on leaves - curling & distortion
Symptoms: upward rolling of the leaves. This is a common occurrence in mid-summer and is associated with high temperatures and moisture stress. Some tomato varieties, including heavily pruned determinate-type varieties, are more prone to leaf roll.
The most common method of treating leaf curl is to spray sulfur or copper after leaf drop in the fall and again in the spring.
Prevent Leaf Curling
Another sign of magnesium deficiency, this problem can also be tackled with the help of Epsom Salt. Mix two table spoons in a gallon of water and spray your curled foliage with the solution until the leaves look perfect again.
Use ACV for fertilising your plants
Using organic, raw and unfiltered ACV, such as Willy's, is great for your plants due to it containing pulp which has the highest amount of nutrients for your plants! Simply mix water with your apple cider vinegar and pour it into a sprayer or watering can.
Controlling the Spread of Peach Leaf Curl
Manually removing the infected leaves from the tree can help control the spread of Peach Leaf Curl. The discarded leaves contain fungus spores that can overwinter in the soil beneath the tree and reactivate in the spring.
Over-watering.
Overdoing your watering can have a similar effect to underwatering. You may also find your plants produce an excess of foliage but few tomatoes. Leaves might yellow and wither, or they could curl.
Best Treatment for Leaf Curl
Where Leaf Curl has been severe in the previous year, trees can also be sprayed with Yates Liquid Copper Fungicide in autumn when the leaves drop, plus at the first sign of bud swell and again one week later.
Soil that contains a lot of sand doesn't hold water well and dries quickly. Because of this, tomato plants growing in sandy soil may need to be watered more often, about every three or four days. Clay soil, on the other hand, holds water well. Plants growing in clay soil usually only need to be watered once a week.
In addition to too little moisture, overwatering can also cause tomato leaves to curl. In this case, the leaves will usually return to normal and the plant will recover once a good watering routine is established.
Bacterial wilt disease is most commonly found on tomatoes, although other solanaceous plants such as potato, pepper, and eggplant also may be infected. The first symptom is a sudden and permanent wilting of the leaves, even when there is adequate soil moisture (Figure 18).