Archive:Poplar/Introduction
From Bugwoodwiki
From: Ostry, Michael E.; Wilson, Louis F.; McNabb, Harold S., Jr.; Moore, Lincoln M. 1988. A guide to insect, disease, and animal pests of poplars. Agric. Handb. 677. Washington, DC: U.S. Department of Agriculture. 118 p.
Poplars are among the fastest growing trees in temperate regions of the world. Intensively managed plantations of genetically superior Populus clones can rapidly produce large volumes of wood for fiber and fuel. In addition, poplars are also valuable for nontimber uses such as ornamental plantings, windbreaks, visual screens, and soil stabilizers.
However, many insects and diseases can threaten the success of poplar plantations by reducing productivity and/or quality of affected trees. Frequently insects and diseases, together with other biotic and abiotic agents, either kill trees or prevent them from reaching their potential growth.
Growers of poplars need to be able to identify the cause of a problem should one develop. Once they know the cause, growers are better able to answer the following questions:
I.What is the expected impact of this condition? II.Will this condition change my management plans and goals? III.Are control measured warranted? IV.What control measures are available?
Although there are several hundred insect pests and pathogens of poplars, only a few of them are potentially dangerous. We have emphasized insects and pathogens that are most likely to be important in poplar plantations in North America. References are provided for obtaining additional information on the major insect pests and diseases.
As poplar culture becomes more intense and widespread, increased exchange of breeding and planting stock may introduce additional insect pests and pathogens into North America. Many of these are destructive elsewhere and could become destructive here as well. For this reason we have included descriptions of the major pathogens elsewhere in the world that could threaten poplar production here unless growers guard against their accidental introductions.
In this guide, we suggest management strategies to minimize injury to trees by insects and disease agents. Direct chemical control is usually not warranted or possible except in nurseries, either because it is not economically feasible or because no chemical is currently registered for use in controlling a specific insect or disease. We advise growers to consult their State and County extension agents for current recommendations because of possible changes in pesticide laws, rates, formulations, and application methods.
Populus is a genus rich in genetic diversity. In addition to the many species of poplars, many interspecific and intraspecific hybrids have exhibited resistance or tolerance to several of the major insects and diseases in this guide. However, growers must be aware that many commercially available clones are extremely susceptible to certain insect pests and disease, making them highly undesirably for most uses. Most of these clones have not undergone field testing in all the locations where they are now being planted, so their pest resistance under different growing conditions is unknown.
In this guide, where we have research data, we make recommendations for or against poplar species or clones with percentages that have exhibited resistance or susceptibility to serious insect and disease injury. We encourage growers to test several clones in their area before planting large numbers of trees.
To identify accurately the cause of an injury, a grower must first carefully examine trees exhibiting abnormalities such as off color foliage, missing foliage, branch dieback, and cankers. These are symptoms of insect infestations and diseases. Note the part of the tree that is affected (for example, lower trunk, upper branches, young shoots, etc.) and the time of year when symptoms develop. Take note of the proportion of trees that are affected and whether there is a pattern of affected trees. For example, are trees with the same symptoms grouped or scattered throughout the planting? Try to find signs of the casual agents such as fungus fruit bodies, insects, webs, and eggs, on or next to the injured tissues. For individuals with access to a microscope, illustrations of spores are included in the descriptions of fungi that cause similar symptoms. Because a complex of factors is often involved, take care in attempting to diagnose the primary cause of injuries.
After carefully examining the affected trees, use the illustrations, descriptions, and the descriptive key in this guide to identify various injurious agents. In some cases injuries resulting from several different agents are so alike that it is difficult to distinguish the exact cause. If you can't make positive identification after using this guide, consult a forest entomologist or forest pathologist. Pest management information can be obtained from the Forest Service offices listed on page 117.
