How to Manage Pests

UC Pest Management Guidelines


Yellows (Molybdenum Deficiency)

(Reviewed 11/05, updated 11/05)

In this Guideline:


Crown leaves become bright yellow and margins become necrotic. Leaves are stunted and misshapened. Symptoms move out the runners until the entire plant is affected. Fruit set is eliminated and plants may be killed.


Yellows is the result of a molybdenum deficiency in cucurbit plants. Molybdenum is generally available in high enough quantity for all plant growth. However, under acid soil conditions molybdenum is difficult for melons of some cultivars to absorb. Yellows occurs commonly in the Stanislaus County production areas and has been associated with cut and fill areas along the California aquaduct and the Delta-Mendota Canal.


A single application of sodium molybdate at 200 ppm will result in a complete recovery of affected plants in 2 to 3 days.



[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Cucurbits
UC ANR Publication 3445


R. M. Davis, Plant Pathology, UC Davis
T. A. Turini, UC Cooperative Extension, Imperial County
B. J. Aegerter, UC Cooperative Extension, San Joaquin County
J. J. Stapleton, UC IPM Program, Kearney Agricultural Center, Parlier

Acknowledgment for contributions to Diseases:
W. D. Gubler, Plant Pathology, UC Davis

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