mammals (deer, hare, squirrels, mice, and voles) and some birds (finches). 

 Secondary consumers include predaceous invertebrates, birds (e.g., warblers, 

 vireos, and thrushes), mammals (shrews, mice, weasels, minks, foxes, and 

 bobcats), and reptiles and amphibians (frogs, toads, snakes, and salamanders). 

 Gosz and coworkers (1978) listed the consumers in a New Hampshire deciduous 

 forest in the following order of importance: chipmunks, mice, foliage-eating 

 insects, birds, deer, and hares. 



The biomass of invertebrate consumers is miniscule compared to the total plant 

 biomass. In a pine plantation in England the biomass of foliage-feeding 

 invertebrates ranged from .00004 to .002 ton/acre (.0001 to .005 t/ha) , 

 whereas plant material biomass was 67 tons/acre (150 t/ha; Ovington 1962). 

 Despite these major differences invertebrates form the major food source for 

 most species of birds, reptiles, amphibians, and some species of mammals. 



Of the invertebrate consumers found in forest systems insects are most 

 important. Herbivorous insects are divided into seven groups based on their 

 feeding habits (table 9-11; Franklin 1970). Foliage-feeding insects are the 

 most abundant group but under normal circumstances the foliage consumed is not 

 damaging to the forest. Insect consumption of deciduous leaves in southern 

 Ontario by forest insects was estimated to be 5% to 10% of the leaf surface 

 area, which represented only 1.57o to 2.5% of total net primary productivity 

 (Bray 1961 and 1964). As small as this seems Reichle and coworkers (1973) 

 consider it an overestimate. Under normal circumstances the effect of insects 

 as mortality factors in Maine's forests is insignificant. Total annual 

 mortality of trees averaged <l7o of total growing stock between 1960 and 1970 

 and insects accounted for about 3% of this (Ferguson and Kingsley 1972) . 

 However, overpopulation of insect herbivores has occurred in Maine's forests 

 and the results can be serious. Defoliating insects, such as spruce budworm, 

 gypsy moth, saddled prominent caterpillar, and satin moths sometimes reach 

 high enough populations to cause complete defoliation of host trees. Most 

 trees can withstand this defoliation for a few years but if insect populations 

 remain high the trees die. 



The most destructive defoliator in Maine forests is the spruce budworm, which 

 attacks primarily balsam fir and spruce. A major outbreak of spruce budworm 

 occurred in Maine between 1910 and 1919 (Pistell and Harshberger 1979). The 

 infestation covered the entire state and in all an estimated 27 million cords 

 of wood were killed. The severity of the infestation varied among areas but 

 in some cases up to 95% of the fir and 85% of the spruce was killed over areas 

 of several thousand acres. 



Maine's forests are currently experiencing an outbreak of budworm that began 

 in 1972. By 1979, 6 to 7 million acres (about 40% of Maine's forestland) were 

 infested to some degree. Approximately 3 million acres were seriously 

 infested, with tree mortality approaching 40%. Pesticides (including 

 carbaryl, trichlorfan, and aciphator) are used to control budworm numbers. 

 The spray program peaked in 1976 when 3.5 million acres were sprayed (Pistell 

 and Harshberger 1979). In 1977 and 1978 about one million acres, and in 1979 

 over 2.5 million acres, were sprayed. 



Outbreaks occur in stands of overmature balsam fir under certain weather 

 conditions (warm, dry days in late May and early June). Trees begin to die 

 after 5 years of defoliation and mortality is nearly complete after 8 years 



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10-80 



