Environment
The number of flea beetles emerging in spring from hibernation depends on the severity of winter temperatures. Warm winter temperatures favor the survival of flea beetle vectors and increase the risk of Stewart’s disease. Low temperatures are highly unfavorable for beetle survival. The numbers of emerging adults can be estimated by calculating a winter temperature index by averaging the mean temperatures (expressed in °F) for December, January, and February. If the sum of the mean temperatures is 90°F or greater, the beetles will survive in high numbers and the disease risk is high; if the sum is between 85° and 90°, the risk is moderate to high; 80° to 85°, moderate to low; and a sum less than 80°F represents low risk.
Flea beetles do not survive in the northern half of Illinois due to low winter temperatures. Those found in late spring or summer have migrated from the south. Snow or other winter cover apparently has little effect in providing sufficient shelter to enhance survival of the overwintering flea beetles. Prolonged periods of wet summer weather are unfavorable for beetle multiplication and feeding, while dry weather is favorable. Consequently, although this disease has been found throughout the world, the bacterium has never survived and spread other than in North America. The reason for this is because the disease depends on where Chaetocnema pulicaria occur. In North America, Stewart’s wilt is found in the mid-Atlantic and the Ohio River Valley regions and in the southern portion of the Corn Belt. This region includes parts of Connecticut, Delaware, Illinois, Indiana, Iowa, Kentucky, Maryland, Missouri, New Jersey, New York, Ohio, Pennsylvania, Rhode Island, Virginia, and West Virginia. Stewart’s wilt can also be found in eastern and midwestern states and prtions of Canada, but this depends on whether or not the corn flea beetles survive the winters. Corn flea beetles can transmit the bacteria northward during the summer, but if the insect vectors cannot survive the harsh winter temperatures, then the bacteria cannot be spread. The toothed flea beetle, adult 12-spotted cucumber beetle, seed corn maggot, wheat wireworm, white grubs, and larvae of corn rootworms can also carry Pantoea stewartii from one plant to another during the summer. These pests cannot overwinter and transmit this disease.
Read more about this topic: Stewart's Wilt
Famous quotes containing the word environment:
“A positive learning climate in a school for young children is a composite of many things. It is an attitude that respects children. It is a place where children receive guidance and encouragement from the responsible adults around them. It is an environment where children can experiment and try out new ideas without fear of failure. It is an atmosphere that builds children’s self-confidence so they dare to take risks. It is an environment that nurtures a love of learning.”
—Carol B. Hillman (20th century)
“People between twenty and forty are not sympathetic. The child has the capacity to do but it can’t know. It only knows when it is no longer able to do—after forty. Between twenty and forty the will of the child to do gets stronger, more dangerous, but it has not begun to learn to know yet. Since his capacity to do is forced into channels of evil through environment and pressures, man is strong before he is moral. The world’s anguish is caused by people between twenty and forty.”
—William Faulkner (1897–1962)
“... several generations of slum environment will produce a slum heredity ...”
—Albion Fellows Bacon (1865–1933)