Homeowners with a windbreak or individual pine tree plantings need to be on the lookout for needle blight and be prepared to treat the disease. Many people dont realize pine trees lack the ability to replace lost needles. Needles shed on the interior of a branch will never grow back and therefore it is important to protect against needle blight. I have seen many pines in our area that are looking a little sickly.
There are two common types of blight that affect pine trees Dothistroma needle blight and Sphaeropsis tip blight. Both are prevalent in our area.
Dothistroma needle blight can be severe on Austrian and Ponderosa pines. This blight is caused by the Dothistroma fungus that infects pine needles in May. Most of the time, symptoms wont show up until fall. By that time, it is too late to control the disease.
Therefore, now is an important time to get out and scout trees. Affected needles will be dotted with small (1/8 inch) brown spots bordered by a yellow halo or will show a half-needle symptom where the outer half of the needle turns brown while the inner half remains green.
Protection against Dothistroma needle blight requires an application of a copper fungicide such as Junction, Kocide, Camelot, Monterey Liqui-Cop or Bonide Liquid Copper Concentrate. The fungicide should be applied about mid-May and a second application in mid-June to protect the tree. Thorough spray coverage is essential.
Sphaeropsis tip blight is also a problem for pines. This disease results in the dieback of new shoot growth in the spring. Over the course of several years, the disease can cause severe damage and even death of the entire tree. Symptoms tend to be more prevalent on lower parts of the tree and first appear in late May to early June. New, developing shoots fail to elongate properly and turn yellow or tan.
Again, an application of a copper fungicide can control the disease, but timing is critical. The fungicide must be applied just as the new buds are elongating. Spraying after this critical time will not be effective in controlling tip blight. We are already too late in the year to control tip blight as the fungicide application should have been applied a couple of weeks ago the end of April.
If you have a Scots pine planting, it is a whole different story. Most of these have been lost in the area from pine wilt. Pine wilt is a fatal disease caused by a pine-wood nematode that is transmitted from pine to pine by a sawyer beetle. In general, trees infected with this disease wilt and die rapidly. The needles turn yellow/brown and remain attached to the tree. Nothing can be done for trees infected with this disease.
Keep in mind too that pines do go through a natural needle drop process. Evergreens do not keep their needles indefinitely but will drop them after one to several years. Natural needle drop happens when the older needles on the inside of each branch turn yellow and eventually drop. Needles on the tips of the branches are unaffected. This is a natural process, so no response is needed.
Remember, natural needle drop only affects the needles on the inside of the tree. If the needles on the tips of the branches are yellowing or individual needles are showing spots or bands, then natural needle drop is not the culprit.
If you are uncertain if your pines have a disease, give me a call and I can make a visit to your home to look at them. My services are free of charge.
Krista Harding is a K-State Research and Extension Agricultural agent assigned to South-wind District. She may be reached at [email protected] or 620-244-3826.
