Bacterial wilt is a cucurbit

Cucurbitaceae

The plant family Cucurbitaceae consists of various squashes, melons, and gourds, including crops such as cucumber, pumpkins, luffas, and watermelons...

 disease caused by the pathogen Erwinia tracheiphila, a Gram-negative

Gram-negative

Gram-negative bacteria are bacteria that do not retain crystal violet dye in the Gram staining protocol. In a Gram stain test, a counterstain is added after the crystal violet, coloring all Gram-negative bacteria with a red or pink color...

 bacterium in the family Enterobacteriaceae

Enterobacteriaceae

The Enterobacteriaceae is a large family of bacteria that includes many of the more familiar pathogens, such as Salmonella, Escherichia coli, Yersinia pestis, Klebsiella and Shigella. This family is the only representative in the order Enterobacteriales of the class Gammaproteobacteria in the...

. Cucumber

Cucumber

The cucumber is a widely cultivated plant in the gourd family Cucurbitaceae, which includes squash, and in the same genus as the muskmelon. The plant is a creeping vine which bears cylindrical edible fruit when ripe. There are three main varieties of cucumber: "slicing", "pickling", and...

 and muskmelon

Muskmelon

Muskmelon is a species of melon that has been developed into many cultivated varieties. These include smooth skinned varieties such as honeydew, crenshaw and casaba, and different netted cultivars...

 plants are most susceptible, but squash, pumpkins, and gourds may also become infected. Watermelons are immune to the disease.

Disease transmission

E. tracheiphila is spread between plants by two species of insect vectors, Striped cucumber beetle

Striped cucumber beetle

The striped cucumber beetle, Acalymma vittatum, is a beetle of the family Chrysomelidae and a serious pest of cucurbit crops in both larval and adult stages.-Description:...

s (Acalymma Vittatum) and spotted cucumber beetle

Spotted cucumber beetle

The spotted cucumber beetle is a major agricultural pest insect . In the adult form it eats and damages leaves of many crops, including cucumbers, soybeans, cotton, beans and many others...

s (Diabrotica undecimpunctata). The beetles acquire E. tracheiphila by feeding on infected plants, then carry the bacteria in their digestive tracts. The disease may be spread to susceptible plants through feeding wounds, by way of infected mouthparts or frass

Frass

Frass is the fine powdery material phytophagous insects pass as waste after digesting plant parts. It causes plants to excrete chitinase due to high chitin levels, it is a natural bloom stimulant, and has high nutrient levels. Frass is known to have abundant amoeba, beneficial bacteria, and fungi...

. The bacteria is capable of overwintering in the gut of its insect vectors.

Symptoms and diagnosis

Bacterial wilt is a disease of the vascular tissue

Vascular tissue

Vascular tissue is a complex conducting tissue, formed of more than one cell type, found in vascular plants. The primary components of vascular tissue are the xylem and phloem. These two tissues transport fluid and nutrients internally. There are also two meristems associated with vascular tissue:...

. When a plant is infected, E. tracheiphila multiplies within the xylem

Xylem

Xylem is one of the two types of transport tissue in vascular plants. . The word xylem is derived from the Classical Greek word ξυλον , meaning "wood"; the best-known xylem tissue is wood, though it is found throughout the plant...

, eventually causing mechanical blockage of the water transport system. The first sign of infection, which appears about five days after acquisition, is the wilting of individual leaves on a single stem. However, the disease will soon spread down the runner and then infect the whole plant, causing it to shrivel and die.
There is a diagnostic test for bacterial wilt that can be done in the field. The presence of the E. tracheiphila causes the sap to become a milky color and acquire a sticky consistency. If the stem is cut near the crown and the ends are slowly pulled apart, the sap should form a viscous string.

Treatment and prevention

Once a plant is infected, there is no way of stopping the spread of the disease. Some cucurbit cultivars are less susceptible than others, so it be beneficial to plant these cultivars. However, since wilt-resistant plants have not yet been developed, the most effective way to prevent the disease is to keep beetle populations at a minimum. While various methods of beetle control have been tested, the most effective preventative measure is to keep beetle populations as low as possible

Pest control

Pest control refers to the regulation or management of a species defined as a pest, usually because it is perceived to be detrimental to a person's health, the ecology or the economy.-History:...

 through careful field monitoring and insecticide

Insecticide

An insecticide is a pesticide used against insects. They include ovicides and larvicides used against the eggs and larvae of insects respectively. Insecticides are used in agriculture, medicine, industry and the household. The use of insecticides is believed to be one of the major factors behind...

sprays.