QUESTION: Why are my Afghan pine (Pinus eldarica) tree's needles turning brown and falling off? The trees are deep watered on a regular basis. There are no signs of damage from insects or disease. What can I do about it?
ANSWER: During the summer months with high temperatures many pine tree species will naturally shed some of their older needles. However, if the terminal new growth is turning brown then you need take some action to remedy the situation. Control: Normal, proper watering should continue throughout the growing season. Some think that the monsoon rains water enough. This is usually not the case. Rain is inconsistent both in timing and amount. Another watering problem is with larger pine trees. When young trees are planted a drip system or other watering system is installed to supply the needs of young trees. Perhaps one or two emitters placed near each trunk. This is sufficient while the tree is young, but not as the tree grows older. Emitters must be doubled up or replaced with higher flow emitters and spread out laterally to encourage extended root growth. I have seen mature evergreen trees blown over by a storm when the ground was wet and always the tree had an underdeveloped root system. The cause was poor water application that did not encourage extended root growth.
QUESTION: I have a young spruce tree that is drying up on one side. The needles are falling off and part of the tree is bare. The tree is watered well. The tree is planted three feet from the northwest side of the house. What is the problem?
ANSWER: The tree is probably infected with spider mites. This can be determined by placing a white piece of paper under a branch while giving the branch a quick tap. Spider mites will be dislodged, fall on the paper and look like little specks running around. These animals are not insects but arachnids, members of the spider family. With a magnifying glass you can see that these tiny creatures have two body parts: a head and abdomen, and eight legs. There are numerous species of mites, both harmful and beneficial. Spider mites thrive in hot, dry weather. Trees planted too close to a house will try and push the house over! Also the afternoon sun reflects heat off of the house on to the tree and provides a perfect environment for mites. Control: If proper cultural practices are used predacious mites normally control harmful mites. If mites become a problem washing them off with a hard stream of water can help destroy small infestations. Dormant oil sprays applied during early spring also help keep mites in check. Dusting sulfur is labeled for mites and is an organic treatment. Care must be used when using sulfur during high temperatures because burning of plant tissue may occur. Chemical miticide are available to control severe infestations. Registered products include Kelthane (dicifol) and Omite (propargite). Always follow the label instructions when using any pesticide.