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Cucurbits

General Insect/Mite Management in Cucurbits

Biology and Management of Aphids in Organic Cucurbit Production Systems. This article by Mary Barbercheck, Penn State University, provides an overview of the biology and life cycles, damage from, and management of the most common aphid pests in organic cucurbit crops.

General Disease Management in Cucurbits

Cucurbit Disease Field Guide - A Disease Reference Guide for Cucumber, Melon, Squash and Watermelon. Published by Monsanto Company and Seminis Vegetable Seeds, Inc..

Winter Squash Storage Rots and Their Management - This article by Oregon State University, College of Agricultural Sciences, Department of Horticulture includes photos of the rot symptoms, descriptions of the diseases, and information on how to control storage rots.

General Weed Management in Cucurbits

Weed Management Strategies for Organic Cucurbit Crops in the Southern United States. Mark Schonbeck, Virginia Association for Biological Farming describes how to manage some of the most troublesome weeds of cucurbit crops in the South.

Diseases

Common name: Powdery mildew
Latin binomial: Golovinomyces cichoracearum (formerly Erysiphe cichoracearum) and Podosphaera fuliginea (formerly Sphaerotheca fuliginea)
Host crops: All cucurbit vegetables (e.g. cucumber, cantaloupe, melon, pumpkin, and squash). There are different races of the pathogens.

Photo Source: Lyndon Porter, USDA-ARS

On-Line Resources:

How to Manage Pests: Pests in Gardens and Landscapes: Powdery Mildew on Vegetables. UC IPM Online, University of California

Pacific Northwest Plant Disease Management Handbook: Squash (Cucurbita sp.) – Powdery Mildew

Pacific Northwest Plant Disease Management Handbook: Cantaloupe (Cucumis sp.) – Powdery Mildew

Pacific Northwest Plant Disease Management Handbook: Cucumber (Cucumis sativus) – Powdery Mildew
 

Common disease name: Various viruses of cucurbits
Pathogen names: A complex of viruses is able to infect cucurbits. The most important viruses tend to be Cucumber mosaic virus (CMV), Squash mosaic virus (SqMV), Watermelon mosaic virus I (WMV-1), Watermelon mosaic virus 2 (WMV-2), and Zucchini yellow mosaic virus (ZYMV). With the exception of SqMV, which is seedborne in melon and transmitted by beetles, the other major viruses are transmitted by several aphid species in a non-persistent manner. Minor cucurbit viruses include Tobacco ringspot virus (TRSV), which is mainly transmitted by nematodes (Xiphinema americanun), Tomato ringspot virus (TmRSV), which is nematode transmitted and can overwinter on many weed species without expressing symptoms, and Clover yellow vein virus (CYVV) which is aphid- transmitted.
Host crops: Most cucurbit crops. However, the different cucurbit viruses can differ in host range, including within the Cucurbitaceae. Some of these viruses also infect plants in other families, which is important to know for disease management practices.

On-Line Resources:

Cantaloupe (Cucumis sp.)-Viruses, Pacific Northwest Plant Disease Management Handbook

Cucumber (Cucumis sativus)-Virus Diseases, Pacific Northwest Plant Disease Management Handbook

Mosaic Diseases of Cucurbits, Report on Plant Disease No. 926, Department Of Crop Sciences, University Of Illinois At Urbana-Champaign

Squash (Cucurbita spp.)-Curly Top, Pacific Northwest Plant Disease Management Handbook

Squash (Cucurbita spp.)-Virus Diseases, Pacific Northwest Plant Disease Management Handbook

Virus Diseases of Cucurbits, Cornell University Vegetable MD Online fact sheet

Common name: White mold
Latin binomial: Sclerotinia sclerotiorum
Host crops: Cucurbit vegetables (e.g. cucumber, pumpkin, and squash), pepper, snap bean, carrot, cabbage, cauliflower, lentil, field pea, potato, radish, and many weed species.

White mold infecting of a gourd of a squash plant.			White mold on squash vines.
Photo Source: Lyndon Porter, USDA-ARS

Pathogen bleaches the vines white. Black sclerotia (dormant survival structures) of the pathogen are often produced inside infected vines.
Photo Source: Lyndon Porter, USDA-ARS

On-Line Resources:

Pacific Northwest Plant Disease Management Handbook: Cucumber (Cucumis sativus) – Sclerotinia Stem Rot {White Mold}

Fruit Rots of Squash and Pumpkins: Sclerotinia White Mold, Vegetable MD Online, Cornell University

White Mold of Vegetables, Pest Management Fact Sheet #5084, The University of Maine
 

Insect/Mite Pests

Common name: Melon aphid (cotton aphid)
Latin binomial: Aphis gossypii
Host crops: Cucurbit vegetables (e.g. cucumber, pumpkin, squash and watermelon), eggplant, pepper, and many weed species.

Melon aphids are often found distributed along the midrib on the underside of a host plant. The aphids range from 1.0 to 1.8 mm long (ca. 1/16 inch) and from pale yellow to green to dark green (almost black) with multiple colored individuals in a single colony. There can be winged as well as wingless forms – latter enable the aphid to seek other plant hosts.	Melon aphids, like other aphids, are soft-bodied, pear shaped with long antennae at one end and a pair of cornicles (tailpipes) on the posterior end. The cornicles secrete defensive fluids. Aphids have a long stylet (‘straw’) they stick into the plant to feed on plant fluids. Note the whitish cast skins.	In addition to scouting for aphid colonies, aphids can be detected by copious amounts of glistening honeydew (sticky, sugar-rich fluid voided by aphids) coating the leaves beneath aphid colonies. Honeydew may contain numerous cast aphid skins and black sooty mold that colonizes the honeydew.
Photo Source: Michael Bush, Washington State University Extension, Yakima, WA

On-Line Resources:

Biology and Management of Aphids in Organic Cucurbit Production Systems. eXtension.

Pacific Northwest Insect Management Handbook. Chapter: Vegetables, Section: Pumpkin and Squash pt. 1

Common Insects & Mites: Aphids. Washington State University Hortsense.
 

Abiotic Problems Common to Cucurbits

Problem: Blossom end rot
Cause: Calcium deficiency resulting from various environmental conditions and management practices, e.g., inadequate Ca in the soil, inconsistent water as a result of alternating wet and dry periods that decrease Ca uptake by plants, and even excellent growing conditions such as a period of very bright sunshine and warm temperatures mid-season.
Crops affected: Tomato, pepper, eggplant, and various cucurbits.

Symptoms of blossom end rot on tomato fruit.

Photo Source: Krishna Mohan, University of Idaho

On-Line Resources:

Blossom end rot: Understanding a perennial problem. Michigan State University Extension.

See Diseases, pests, and other problems common to many vegetables: Blossom end rot of vegetables.

Problem: Edema
A physiological problem: prominent when air is cooler than the soil, soil moisture is high, and relative humidity is high. The low plant transpiration rates combined with an increase in water absorption by roots from the soil leads to increased cell turgor pressure, resulting in eruption of epidermal cells as the inner cells enlarge. Protrusion of the inner cells causes epidermal cells to die and discolor, resulting in a ’warty’ appearance that can be misidentified as a disease. In addition to foliar symptoms on some hosts, many cucurbit crops develop wart-like protruberances on the fruit.
 

Severe wart-like growths on a pumpkin caused by edema.	Close-up view of severe edema symptoms on a pumpkin.	Small but extensive symptoms of edema on a winter squash.	Close-up view of edema symptoms on the surface of a winter squash.
Photo Source: Lindsey du Toit, Washington State University.	Photo Source: Phil Hamm, Oregon State University.	Photo Source: Lindsey du Toit, Washington State University.

On-Line Resources:

Pumpkin and Squash Production Factsheet: Oedema, Ontario Ministry of Agriculture, Food and Rural Affairs

Edema - General Principles Information Note 3 (VDIN-003), North Carolina State University Plant Pathology Extension

What are these bumps on my vegetables? Edema or oedema: It doesn’t matter how you spell it, it still doesn’t look good. What is it, what causes it and how can I prevent it? Michigan State University Extension