The best way to control diseases in your tulip bed is to practice good garden hygiene. Find facts and information on choosing tulip bulbs, recognizing and avoiding tulip diseases. General info on tulips can also be found: 'Tulip (tulipa)Facts and Information Guide", or "Caring and Storing Tulip Bulbs."
It is important to purchase the very best quality bulbs and avoid late season discount offers which are more than likely to be smaller and often damaged bulbs. You will find that bulbs exported fro the Netherlands are carefully controlled to eliminate diseases and must be at least a size of 10 or greater. Size is very important for guaranteeing top-quality flowers.
Choosing Tulip Bulbs
Sizing tulips for your tulip garden, is based on the circumference of the bulb. So, a 10 bulb would be 4 inches around equalling 10 centimeters. Sizes of 11 or 12 or not uncommon, especially with some of the larger varieties, such as Darwinhybrids or Single late group tulips. If you look in a bulb catalogue you will find the size of the bulb, in centimeters, marked in the description of the tulip. Note that smaller tulip varieties will only be a 5 to 8 and will never get any larger because that is the nature of that particular species of tulip.
Tulip Planting Tips, Pest, and Diseases
When you are planting it is important to make sure that the bulbs in your tulip garden are not bruised or damaged in any way. At this point, one of the biggest problems you may have is that mice as well as other gnawing animals such as: rats, squirrels, moles, chipmunks and raccoons. Be careful to not leave any portions of the tulip, such as tunics, laying around in your tulip garden or bed, as they will mark the spot for the animals to come and dine.
To avoid pest after planting your bulbs, you may try to put a thick layer of gravel over them. It seems when the pest do come, it is right after you plant them. The gravel will fall in onto the mice before they can get to the bulbs. If you have expensive bulbs planted, it would be worthwhile to do this.
Other soil predators include slugs, wireworms and nematodes. These can be controlled with chemicals. If you have well prepared soil, you should not have any problem with these pests.
The most serious disease you are likely to have is tulip fire, or botrytis. This is a disease caused by the fungus botrytis tulipae. Be assured that this disease has been diligently fought against on any bulbs you may get, but once they are planted they can get this disease. Any type of damage to the top of your bulb can serve as an entry point for fungus. If you have had a period of frost or hail, you could very easily get this fungus. It spreads very quickly when conditions are damp and rainy. The leaf tips of infected plants become yellow and shrivel up. Their shoots may be twisted and the leaves deformed or streaked with red. Round to oval spots can appear on the leaves, first yellow then gray brown with wet edges. At this stage the spots are known as lesions.
In wet weather, whole flowers and stems may become covered with mold and will eventually will form dark pin-shaped places that are called sclerotia. These can fall onto the ground and will remain viable for a number of years. It is important not to plant your tulips in the same place for several years, because of this fact and possibility of being infected.
Other fungal disease such as botrytis parasitica and gray bulb rot (Rhizoctonia tuliparum) can affect your bulbs. Infected bulbs will either fall to grow or appear with stunted or shriveled shoots and leaves.
The risk of disease occurring increases when bulbs are left in the ground from one year to the next. So it is important to be aware of this situation or dig up your bulbs each year to keep them healthy.
To conclude: Use top quality bulbs which are planted in good workable soil. Don’t overly fertilize or over water your bulbs. If possible, replant in a different site each year. Try to remove any fallen petals or dead leaves to keep disease from starting. Never add any of these stems or petals to your compost pile as could be storing up diseases that can be spread back into your tulip bed or other soil surfaces.
*Don't forget to get your snowblower in shape for the winter to come.