{"id":49564,"date":"2022-12-02T11:31:37","date_gmt":"2022-12-02T11:31:37","guid":{"rendered":"https:\/\/dev.metos.global\/?page_id=49564"},"modified":"2026-05-04T09:39:46","modified_gmt":"2026-05-04T09:39:46","slug":"disease-models-lettuce","status":"publish","type":"page","link":"https:\/\/metos.global\/en\/disease-models-lettuce\/","title":{"rendered":"Disease models – lettuce"},"content":{"rendered":"\t\t
\n\t\t\t\t\t\t
\n\t\t\t\t\t\t
\n\t\t\t\t\t
\n\t\t\t
\n\t\t\t\t\t\t
\n\t\t\t\t
\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\"Disease\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
\n\t\t\t\t\t\t
\n\t\t\t\t\t
\n\t\t\t
\n\t\t\t\t\t\t
\n\t\t\t\t
\n\t\t\t\t\t

Lettuce <\/b>disease models\n<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
\n\t\t\t\t
\n\t\t\t\t\t\t\t\t\t

\u00a0<\/p>

Downy Mildew, Grey Mould and Leaf Spots of Lettuce:<\/strong>\u00a0Lettuce is susceptible to various fungal pathogens (Bremia lactucae, Botrytis cinerea, Septoria lactucae, Cercospora longissima, Microdochium panattonianum<\/em>) and bacterial pathogens (Xanthomonas campestris pv. vitians<\/em>) causing damages on leafs, mould in the head and leaf spots. Because the leaf is the harvested product, Downy Mildew, Grey Mould and Leaf spots can cause considerable damage under the right environmental conditions. In the present version\u00a0FieldClimate is offering Models for the Infection by Downy Mildew, an Infection Model for Anthracnose and a Risk Model for Grey Mould<\/u>.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

\n\t\t\t\t\t\t
\n\t\t\t\t\t
\n\t\t\t
\n\t\t\t\t\t\t
\n\t\t\t\t
\n\t\t\t\t\t

DOWNY MILDEW \u2013<\/br>Bremia lactucae<\/em><\/a><\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t
\n\t\t\t
\n\t\t\t\t\t\t
\n\t\t\t\t
\n\t\t\t\t\t

ANTHRACNOSE \u2013<\/br>Microdochium panattonianumis<\/em><\/a><\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t
\n\t\t\t
\n\t\t\t\t\t\t
\n\t\t\t\t
\n\t\t\t\t\t

GREY MOULD \u2013<\/br>B. cinerea<\/em><\/a><\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
\n\t\t\t\t\t\t
\n\t\t\t\t\t
\n\t\t\t
\n\t\t\t\t\t\t
\n\t\t\t\t
\n\t\t\t\t\t\t\t\t\t
\n\t\t\t\t\t\n\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\tRecommended equipment<\/span>\n\t\t\t\t\t<\/span>\n\t\t\t\t\t<\/a>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
\n\t\t\t\t\t\t
\n\t\t\t\t\t
\n\t\t\t
\n\t\t\t\t\t\t
\n\t\t\t\t
\n\t\t\t\t\t\t\t
\n\t\t\t\n\t\t\t\t\t\t<\/span>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t
\n\t\t\t\t\t\t
\n\t\t\t\t\t
\n\t\t\t
\n\t\t\t\t\t\t
\n\t\t\t\t
\n\t\t\t\t\t\t\t
<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
\n\t\t\t\t
\n\t\t\t\t\t

Downy mildew<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
\n\t\t\t\t
\n\t\t\t\t\t\t\t\t\t

Downy mildew\u00a0(Bremia lactucae<\/em>) is a common fungal disease of lettuce\u00a0in cooler growing regions. In some areas growers report that 60% (or more) of the total fungicide spray applications on a lettuce crop specifically target this disease. A program that provides good disease control, yet decreases use of downy mildew fungicides, would significantly reduce the total use of pesticides on lettuce.<\/p>

Symptoms<\/h3>

Leaf symptoms of downy mildew first show as angular, pale yellow patches which are delineated by leaf veins. The first leaves of the lettuce plant or older leaves close to ground usually are the first to show symptoms. The underside of the leaf opposite the yellow patch will show white masses of spores from 7 to 14 days after infection. As the spore mass grows larger, it takes on a white, downy appearance; hence the name downy mildew.<\/p>

Pathogen<\/h3>

Life Cycle and Requirements of the Organism:<\/span>\u00a0Infection occurs when a downy mildew spore (conidium) germinates and enters the lettuce leaf via direct penetration of epidermal cells. Entry through leaf stomata also occurs. Colonization occurs when intercellular hyphae of the fungus grow and penetrate new lettuce leaf cells, utilizing the nutrients found in these plant cells. This systemic infection can proceed rapidly. When weather conditions are right, sporulation occurs when hyphae accumulate under leaf stomata. Conidiophores bearing conidia emerge from the stomata. Wind disseminates the conidia to repeat the infection process. Conidia may also form into zoospores that either directly infect leaf tissue or become encysted for later infection.<\/p>

Life Cycle of\u00a0Bremia lactucae<\/em>, the lettuce downy mildew pathogen\u00a0Conditions for Sporulation:<\/span>\u00a0Like in all Downy Mildew Pathogens Sporulation takes place during night under high relative humidity and sufficient temperature.<\/p>

Conditions for Spore Dispersal:<\/span>\u00a0Falling relative humidity or sunrise\u00a0seem to be responsible for spore dispersal.<\/p>

FieldClimate Downy Mildew Infection Model<\/strong><\/h3>

The model is based on the work done in the group of Arianne Van Bruggen in UCDavis. We adopted it to a climate where rain can be the source of leaf wetness during the summer. The key climate and epidemiologic factors are:<\/p>