Treesearch

Woody plant resistance to insect damage is of great importance in forest protection, and tree tolerance is an important element of this resistance. The compensating mechanisms responsible for tolerance are nonspecific as a rule and develop after damage has been caused by phytophagous animals or other unfavorable effects. Beyond that, plant tolerance depends on duration, repetition, and phenological periods of the damage effects, and on environmental conditions. We have studied of radial increment patterns in trees as a measure of their physiological state. This approach may be tested in...

One of the characteristic features of the gypsy moth population in the Lower Dnieper area is its variable larval coloring. Phenotype frequency has been recorded over the years in separate micropopulations at different density levels. The data show the population to consist mainly of gray larvae in all life stages, and their abundance varying from 85 to 99.6 percent. Larvae with a black stripe along the back (black type) range from 0.4 to 15 percent of the population. Depending on the phase of population gradation, the phenotype concentrations in a population can vary. At high and low...

At least 10,000 species of leafminers in four orders of insects (Lepidoptera, Diptera, Coleoptera, and Hymenoptera) are found worldwide. The common feature of all leafminers is that larvae feed within leaves for at least some larval stages. Larvae of facultative mining species feed internally but also externally as free-feeders, usually in later larval instars. Larvae of obligate mining species feed exclusively, and may also pupate, within leaves (Hering 1951, Powell 1980). Despite wide interspecific variation in life histories, leafminers are generally more closely associated with their...

Structural and functional changes in forests due to anthropogenic factors have a considerable impact on the interaction of phytophagous insects with the phytocenosis. Many features of these processes have yet to be investigated in the deciduous forest conditions of the forest-steppe zone. We investigated birch forests disturbed by anthropogenic factors in the middle and southern Urals. Anthropogenic transformation stages were determined using geobotanical analyses of grass (Polyakova 1983), physiological and chemical analyses of soil, and analyses of forest stand structures and the...

Lepidoptera is a relatively young order and one of the largest and most diverse in the Insecta. The first paleontological vestiges of moths were found among lower Jurassic deposits, but the most intensive lepidopterous evolution (mainly in suborder Ditrysia = Papilionina) took place in the mid-Cretaceous Period, coterminous with the expansion of angiosperm plants. The flowering plants were a highly determinant factor in the development of the environment, their influence on moth speciation extending beyond provision of food for caterpillars and adults. The greatly increasing heterogeneity...

Five piercing and sucking insects which were accidentally introduced from Asia during this century, together with one native species, have become very serious pests of two important forest tree species in the northeastern United States. Two armored scales, Fiorinia externa Ferris and Nuculaspis tsugae (Marlatt), and an adelgid, Adelges tsugae Annand, attack eastern hemlock, Tsuga Canadensis Carriere (Fig. 1). A margarodid scale, Matsucoccus resinosae Bean and Godwin, and two adelgids, Pineus boerneri Annand and Pineus coloradensis (Gillette), attack red pine, Pinus resinosa Aiton (Fig. 2).

Interrelations of the bud gall midge and the Siberian larch are of scientific and practical interest because of the bud gall midge's role as a plant endoparasite. We know that attack by the gall midge sets off a reaction in the entire plant. Invasion by the insect results in a certain interaction between physiological mechanisms of the insect and the plant which leads to a complex range of interdependent shifts in the metabolism of the tree, the final result depending on the character of those shifts. The reactions of both the plant and the insect are determined both by genetic factors and...

The objectives of this paper are: 1) to provide a general overview of adelgid biology and the various host relationships; 2) to review the current knowledge of the interactions of the balsam woolly adelgid, Adelges piceae (an introduced pest), and its North American hosts; 3) to report on the most recent research involving the interactions of this adelgid with Fraser fir, Abies fraseri., in the southern Appalachians; and 4) to provide a synthesis of the above in the form of an hypothesis regarding host tolerance for the balsam woolly adelgid.

Intensive herbivory may influence the resources available to the next generation of herbivore in three ways: quantity may decrease, be unchanged, or increase. There are now two good examples of the last possibility. One of them concerns Monochamus beetles on firs in Siberia (Isaev et al. 1984), and the other a galling sawfly on willow in Arizona (Craig et al. 1986). The highly intimate and sedentary way of life of galling insects should predispose them to evolve the means to manipulate their hosts. Therefore, it is not surprising that a third example which we report herein deals also with...

The family Cecidomyiidae is one of the largest of the Diptera. Gall midges are small, inconspicuous flies, but they may be very important both in forest ecosystems and in agroecosystems. Many phytophagous gall midge species attack forest trees, and some of them can be serious pests, such as the Dasineura rozhkovii Mamaev and Nikolsky, which develops in bud galls of Larix sibirica Ledeb (Isaev et at 1988). More than 1,200 species in 125 genera are known to occur in the Nearctic Region (Stone et al. 1965), and about 2,200 species in 300 genera occur in the Palearctic Region (Skuhravá 1986)....