Maple Leafcutter Moth Larvae Descending
This time of year it looks like someone has visited every other Sugar Maple (and to a lesser extent, Red Maples and birches) leaf with a hole punch. The Maple Leafcutter Moth (Paraclemensia acerifoliella) is the hole-punching culprit. At the beginning of the summer, leafcutter larvae hatch and begin mining tissue between the upper and lower layers of maple leaves. The mines are barely discernible, as the larvae are so small at this stage. A bit later in the summer the larvae start using their mandibles to cut out round discs of leaf tissue. They take two of these discs and fasten them together with silk, forming a protective case around themselves as they consume additional tissue between the leaf veins. It is this feeding that causes the “punch holes.” As the larva grows, it cuts larger and larger discs to form its case.
When September comes, the larvae are mature and descend to the ground, carrying their homes with them as they move into the topsoil to pupate. Orange-headed, metallic blue-winged adult moths will emerge in the spring, leaving their leaf homes behind.
Because leaves have produced most of the sugar they are going to produce by late summer, the feeding behavior by the moth larvae that occurs from August until leaf fall isn’t a threat to the health of the tree unless complete defoliation occurs for three consecutive years or more.
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Porcupine Trails
Porcupines are forced to exert a lot of effort if they are in need of food and the snow is deep. Unlike many rodents that are light enough to travel on top of the snow, Porcupines must plow their way through it. Their weight, short legs, and bare footpads make traveling in snow challenging, to say the least.
If the snow is deep, the winter ranges of Porcupines are considerably smaller (18 acres in one research study) than their summer ranges (160 acres in same study). Because of the energy needed to travel through the snow, Porcupines usually feed just a short distance from their winter dens, more often than not within 200 feet. Their feeding trails from rocky or hollow tree dens to their woody food sources (often Eastern Hemlock-note bits of branches on snow in photo, American Beech and Sugar Maple), are very distinctive. They are used every night when Porcupines leave their dens to feed and again several hours later when they return. These trails become well marked with urine, and less frequently with scat and quills. (Photo insert: Porcupine rock den entrance)
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Early Splashes of Maroon
At this time of year, our eyes are immediately drawn to the brilliant orange, red and yellow pigments of Sugar Maple (Acer saccharum) leaves. However, there’s much to be said about the less flamboyant splashes of color adorning some of the species of trees that provide New England’s spectacular fall foliage. One such subtley-colored fall tree that often grows in upland forests along with Sugar Maples is White Ash (Fraxinus americana). One of the first trees to change color in autumn, White Ash can turn shades of yellow, orange and red, but deep red, maroon and purple are typically the grand finale of this species. Often its leaves progress from green to yellow and eventually maroon. While it might not be the first tree that catches your eye, make a point of looking for its colorful, compound leaves – you won’t be disappointed.
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Yellow-bellied Sapsuckers Have Varied Diet
Yellow-bellied sapsuckers are just starting to arrive on their northern breeding grounds. As you might assume from their name, these birds feed on the sap of trees. Their horizontal lines of drilled holes are a familiar sight, especially in trees such as paper birch, yellow birch, sugar maple, red maple and hickory, all of which have a high concentration of sugar in their sap.
In addition to sap, yellow-bellied sapsuckers also eats insects (primarily ants), and spiders, probing underneath bark to find them. They’ve even been observed “hawking”– taking off from a branch and scooping up insects in the air.
Lesser known is the fact that sapsuckers also consume vegetation, including the inner bark and cambium layers of trees, the buds of trembling aspen, and a variety of fruits and seeds. The recent cold snap had the pictured male yellow-bellied sapsucker scarfing down crab apples before the sun set. (The next NC post will be on 4/11/15.)
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Bud Scales
Much of this coming summer’s woody plant growth is contained in embryonic form inside a tree’s buds. Buds contain an undeveloped shoot, leaf, and/or flower. Formed last summer, these buds must survive the freezing and fluctuating temperatures, relatively dry air and the potential insect, bird and fungal damage that may occur during the fall, winter and early spring.
Bud scales, which are small, modified leaves, cover and protect many of these buds. The number of scales, their arrangement, color, presence or absence of hairs or sticky substances are often distinctive. Willows have one visible bud scale (actually two fused into one), whereas pine and fir buds may have anywhere from 100 to 350. The scales on a bud can either be arranged in pairs facing each other edgewise (American Basswood, pictured) or overlapping like shingles (Sugar Maple, pictured). Colors range from the wine-colored bud scales of Striped Maple to the mustard yellow Bitternut Hickory scales. The texture of bud scales has great variation, including the satiny-smooth hairy bud scales of Box Elder (pictured). Many bud scales, such as poplars, are covered by a gummy substance which serves as added protection.
A few trees and shrubs have buds that lack scales. These are referred to as “naked” buds, and often the embryonic leaves are quite hairy. Witch Hazel, Hobblebush and Staghorn Sumac (pictured) are species of woody plants lacking bud scales.
Most buds have multiple scales which, upon falling off when the bud opens, leave a series of horizontally-elongated scars on the surface of the growing stem. By means of these scars one can determine the age of a young branch, since each year’s growth ends in the formation of a terminal bud which produces an additional group of bud scale scars. Continued growth of the branch causes these scars to be indistinguishable after a few years so that the age of older branches cannot be determined by this means.
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Gall-making Mites on Sugar Maple Leaves
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Within a week or two of unfurling, Sugar Maple leaves are attacked and consumed by all kinds of creatures, some of which are insects and mites that cause the leaves to develop abnormal growths called galls. Certain species of eriophyid mites form felt, or erineum, galls, often on Silver and Sugar Maple leaves. After spending the winter months under the scales of buds, these mites emerge in the spring when leaves appear, move out onto the surface of the leaves and begin to feed. Their feeding induces the growth of thousands of tightly-packed leaf hairs which provide shelter for the mites on the leaf surface. These hairs appear as bright pink or red patches that resemble felt. The mites, too small to even be seen with a hand lens, move to the inside of these structures for the rest of the growing season.
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Sugar Maple Seeds & Sap
Cold nights and warm, sunny days increase the amount of the sap flow in a Maple Sugar tree, making weather an important factor in the quality of a sugaring season. But it’s not the only factor. Both the amount of sap flowing as well as its sugar content affect a given season’s maple syrup production.
Recent research indicates that the size of a tree’s seed crop in the fall is a good predictor of the sugar content of its sap the following spring. A tree, through photosynthesis, produces and stores a given amount of carbohydrates. These carbohydrates are utilized in the production of seeds as well as the production of sugar. Once the carbohydrates are used up, over a year is needed for the tree to replace them. If a lot of seeds are produced in the fall, there are fewer carbohydrates available for the production of sugar the following spring. Hence, while the weather in a given spring may be conducive for the ample flow of sap, the sap that flows may have a very low sugar content if a tree produced a lot of seeds the previous fall, making it necessary to boil more sap to achieve the desired sugar content in the maple syrup. (Source: Northern Woodlands magazine)
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Red Squirrels & Sugar Maples
We’re approaching what is often a very stressful time of year for many animals, including red squirrels. In the fall they feed on all kinds of conifer seeds, mushrooms, insects, nuts and the many fruits and berries that are available. They also have caches of cones, which they turn to once there is a scarcity of food elsewhere.
Once these caches are used up, usually by late winter or early spring, red squirrels turn to sugar maples for nutrients. Their timing is perfect, for this is when sap is starting to be drawn up from the roots of trees. Red squirrels are known to harvest this sap by making single bites into the tree with their incisors. These bites go deep enough to tap into the tree’s xylem tissue, which is where the sap is flowing. The puncture causes the sap to flow out of the tree, but the squirrel delays its gratification. It leaves and returns later to lick up the sugary residue that remains on the branch after most of the water has evaporated from the sap.
Not only do red squirrels help themselves to sugar maple sap, but they have developed a taste for the buds, and later in the spring, the flowers, of both red and sugar maples. Red squirrels are not the only culprits – gray squirrels and flying squirrels also make short work of buds and flowers from these trees.
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Ice-coated Tree Buds
Recently freezing rain coated trees with ice and the sight reminded me that when a freeze is threatening fruit trees in the spring, just as buds are breaking, orchardists often opt to replicate this phenomenon by starting a sprinkler and coating their trees with ice. Flower buds that are starting to open can be extremely temperature sensitive, suffering damage when it goes below freezing even temporarily. As counter-intuitive as it seems, a properly maintained layer of ice works well to protect opening buds from the cold. When water freezes, heat is produced at a rate of 80 calories per gram of water (the heat of fusion). If water is continually applied to the tree and consistently freezes, it is possible to maintain the buds around 32 degrees F., thereby protecting the flowers within them. (Photo- sugar maple terminal buds)
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