In recent years, a disease, steadily increasing in severity, has ravished many pine plantings. The Austrian pine is the most seriously affected species in the Midwest, with older trees dying by the hundreds.
The disease is called Sphaeropsis tip blight of pine and is caused by a fungus, Diplodia pinea.
The pattern of infection reveals much about the nature of the disease-causing organism. Fr example, the fungus infects and damages or kills very old pine trees, pines growing in poor soil, perhaps also exposed to a severe environment, and large pines recently transplanted.
All of this suggests that the fungus prefers to attack trees in poor health or weakened by bad conditions. However, pines growing in deep, rich soil with ample water throughout the year, and treated to an occasional feeding, seem to resist the disease successfully.
Why should older or recently transplanted pines be subject to infection? The Midwest, south of central Minnesota, is prairie country—hot, dry and windy in summer and cold, dry and windy in winter.
How Hard Pines Are Affected
Hard pines are found naturally in cool, windless countries wrapped with mists and wet snows. Unfortunately, prairie climates are unkind to hard pines.
When a tree is transplanted, the disturbed roots cannot furnish enough water and minerals to aid the top in its struggle, and the plant is weakened.
Old trees have depleted the soil around their roots, but the large top goes on, demanding water and food out of balance with what is available from the roots. The drought of the ’50s probably permitted the disease to start in the Midwest and become general.
How To Control The Tip Blight
Curbing the disease is relatively simple, although expensive if a large planting is involved. Sanitation comes first. Rake up and burn all needles under infested trees; fungus spores are found in such debris.
Prune out dead tips to soft, live wood and flexible, green needles; burn this material. If large limbs are to be pruned, paint the cuts with tree paint.
Now the tree is ready for spraying. With one exception, fungicide sprays of young Austrian pines. The center tree on either tree, where lips have turned, has become twisted.
Are preventive in action? That means that they must be on the plant before it is diseased. They do not cure an already infected plant (although they may destroy spores being formed on the surface of the leaves and twigs).
This fungus releases its spores on warm, humid spring days. The wind-borne spores infect the unfolding “candles” of pine trees. Therefore the spray must be aimed at the tips, and as these tips expand, more spray must be applied.
Begin with the first active growth of the “candles,” usually around the first of April, and renew the spray about every ten days to two weeks for three sprayings. All hard pines ought to be sprayed.
What To Use
Plant pathologists generally recommend fungicides are standard Bordeaux mixture, fermate, or the distances (Dithane Z-78, Manzate).
Any of these, made up according to the manufacturer’s recommendations for woody plant sprays for fruit trees (few packages carry specific recommendations for pine), will give good control.
The coverage must be complete. Add a sticker spreader or a little flaked soap to aid the chemical in coating the new shoots thoroughly.
Good sanitation and three sprayings at the right time each year ought to clean up an infection in two years.
Meanwhile, build up the tree’s health, and feed it two or three pounds of 6-10-4 fertilizer for every inch of trunk diameter.
Dig, do not pound, holes every 18” inches from a foot outside the drip line .of the branches halfway toward the trunk, and distribute the allotted amount of fertilizer in the holes.
Keep it within 6″ inches of the surface. Then, any time rain is not forthcoming through the summer, use a root waterer and soak the soil in the same area.
Only let the tree go with water for up to two or three weeks. Then, your healthier pine will not only resist tip blight but will look and grow better.
One final word. This is a lot of work, but it has benefited the community. You, in turn, deserve a little consideration from your pine tree-growing neighbors, so encourage them to care for their trees.
Nobody wants a horticultural version of Typhoid Mary in his backyard, especially when a little effort is so rewarding in preventing the disease.
44659 by Na