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Stewart's Wilt is a serious bacterial disease of corn caused by the bacterium ''Pantoea stewartii''. This bacterium affects plants, particularly types of maize or corn such as sweet, flint, dent, flower and popcorn. The disease is also known as bacterial wilt or bacterial leaf blight and has shown to be quite problematic in sweet corn in the gram negative state of bacterium. The disease is endemic in the mid-Atlantic and Ohio River Valley regions and in the southern portion of the Corn Belt including parts of the following states: Arkansas, Delaware, Illinois, Indiana, Kentucky, Maryland, Missouri, New Jersey, New York, Ohio, Pennsylvania, Tennessee, Virginia and West Virginia. The occurrence of Stewart's wilt in other eastern and mid-western states, and intermittently in Canada, coincides with the occurrence of the corn flea beetle (Chaetocnema pulicaria), the insect vector and overwintering host of P. stewartii. The primary vector of ''Pantoea stewartii'' is the corn flea beetle, (''Chaetocnema pulicaria''). The bacterium overwinters in the gut of the adult beetle during the winter and come spring, is spread when adult beetles feed on the plant seedlings.〔 The bacteria have also been known to spread from the endosperm of the plant seed to the young seedlings, but this is quite rare and its incidence is insignificant compared to insect transmission.〔 Thus, survival of the insect vector through the winter months, especially in the north central U.S., is the key factor in development of the disease. The disease manifests in two phases: seedling wilt, when the growing point dies; and leaf blight, white lesions on the leaves of older plants. Sweet corn has proven to be more susceptible than field corn, although some hybrids and inbreds of popcorn and field corn are highly susceptible. One of the first forecasting systems designed was for preventing Stewart's Wilt. Apart from forecasting, Stewart's wilt severity can be controlled effectively through use of insecticides and resistant hybrids of corn, with resistant hybrids being the best means of control.〔 ==Hosts and symptoms== Stewart's wilt can be a serious disease of many corn types, including: sweet, dent, flint, flower, and popcorn.〔 Sweet corn and popcorn cultivars are more susceptible to Stewart's wilt than field (dent) corn, but there are some dent corn inbreds and hybrids that are susceptible. The production of virulence factor can be caused by the communication system between the bacteria known as quorum sensing Stewart's wilt causes yield reductions by decreasing the size of corn stand or by limiting the production of corn. This results in fewer and smaller ears of corn. Stewart’s wilt has two phases of symptoms: the wilt phase and the leaf blight phase. For both phases, symptoms first appear as leaf lesions, initiating from corn flea beetle feeding scars. At first, the leaf lesions appear long and irregularly shaped and are light green to yellow and later on, straw colored. On mature plants, yellowish streaks with wavy margins extend along the leaf veins.〔 This leaf blight phase is often prevalent after tasseling and the symptoms look similar to frost damage, drought, nutrient disorders, northern corn leaf blight (caused by ''Exserohilum turcicum''), and particularly Goss's wilt (caused by ''Clavibacter michiganensis'' ssp. ''nebraskensis'').〔 A good way to determine if the corn is facing symptoms from Stewart's wilt is to look at the leaf tissue under microscope. If the bacterial ooze exhibits nonflagellate, non-spore-forming, rod-shaped bacterium, there is a great chance it's Stewart's wilt.〔 The corn flea beetle feeds on corn leaf tissue and then transmits the bacteria, ''Pantoea stewartii'', into the plant. When large populations of corn flea beetles are feeding, skeletonization of leaves and death of seedlings can occur. In most cases, the wilt phase occurs on seedlings, but for certain corn types (i.e. sweet corn) more mature plants can become wilted. The wilt phase is systemic, meaning the majority of the plant is infected via bacterial movement and colonization of the plant's vascular system. When the bacterium spreads within the plant, leaves begin withering and can die. Plants become stunted and at times, the whole plant may wilt and die. Dwarfed, bleached tassels are common. Often, plants that have wilt symptoms will also have leaf blight symptoms. When the bacteria reach the corn stalks, the vascular bundles become brown and necrotic. A good indicator of whether or not the bacteria has infected the stalks is if there are yellow masses of bacteria oozing from the vascular bundles. With certain sweet corn hybrids, yellow, slimy ooze collect on the inner ear husks and/or cover the corn kernels. It is possible that the kernels may also have grayish lesions with dark margins or they may be irregular in shape and dwarfed. Another common symptom of the bacteria is formation of open cavities within the stalk tissue. While the plants are weak and vulnerable, stalk rot fungi can further invade the corn plant.〔(Integrated Pest Management – Stewart's Wilt and Blight of Sweet Corn )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Stewart's Wilt」の詳細全文を読む スポンサード リンク
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