Gall rust on pines
Globose swellings on the main stems and branches of two- and three needle pines (mainly jack and Scots, but occasionally on Austrian and Mugo) are caused by eastern or western gall rust fungi. Tree parts distal to the galls eventually die, or break off while still alive from wind or heavy snow effects. Orange, dust-like spores of western gall rust are produced on the gall surfaces during April through June and are wind blown to infect other pines. Identical spores of eastern gall rust are released during the same period and are wind blown to infect young oak leaves. The fungi that develop on these leaves produce spores that can infect other oak leaves on the same or different oak trees. During early summer spores from the oak leaves are wind carried back to pines. To control both of these gall rusts, remove galls as they develop and before they form orange spores (two to four years after infection).
Some spruce on a few scattered sites in central Minnesota have chlorotic/ yellow needles this spring, but the length of last year's shoots and needles seemed normal. No fruiting bodies or insect depredations were found. Where shoot growth is normal, but needles are yellow for one or more years, it's likely that the cause is physiological. And waterlogged soil was present. In waterlogged soil, plant roots and soil organisms quickly deplete gaseous oxygen, carbon dioxide increases, iron and manganese are reduced to insoluble forms and various toxic products accumulate. If the drainage returns to normal before the new growth occurs in May and June, the new shoots should be normal in color and length. Such conditions have been observed in areas bordering swamps where drainage appears to have irregular patterns, causing yellowed spruce to grow near green spruce. An early spring check for waterlogged soil occurring only in the vicinity of the yellowed spruce should confirm these conditions.
If the needles are yellow and the length of needles and stems are shorter than normal, then the cause may be a nutrient deficiency. This can be remedied by the application of soil nutrients or liming or acidifying compounds. Before rushing out to buy them, though, take advantage of the U. of Minn. Extension Service soil testing. Soil test kits are available from Extension Offices in each county.