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Major pests and diseases of cucumber - Global overview ​

Overall picture of pest damage to cucumbers ​

Cucumbers are fruit vegetables that prefer a warm environment, and are susceptible to a variety of pests and diseases on their leaves, stems, and fruits. Growth inhibition due to sap-sucking pests, reduction in yield and quality due to leaf-eating pests and fruit-eating pests, and foliar expansion due to virus-mediated and fungal diseases are important management issues regardless of the cultivation method (open field or greenhouse) and region. In this article, we will summarize the damage symptoms, occurrence, and distribution of the major cucumber pests (aphids, spider mites, cucurbit beetles, thrips, etc.) and major diseases, including white powder, that are recognized in Japan and around the world.

Suice-sucking pests (including virus vectors) ​

Aphis (Aphis gossypii, Myzus persicae, etc.) ​

  • Details of damage: Clumps on leaves and shoots and sucks sap. Yellowing and curling of leaves, soot disease caused by honeydew, and growth retardation. Vectors such as cucumber mosaic virus (CMV).
  • Distribution/Characteristics: Important both in open fields and greenhouses throughout the world and in Japan. It occurs frequently during the warm season from spring to autumn [1][2][3].

Spider mites (Tetranychus urticae, etc.) ​

  • Details of damage: Suck is sucked on the underside of the leaf, resulting in spot discoloration and yellowing, and in severe cases, browning and defoliation of the leaves. Spread a spider web-like thread. Propagates rapidly in dry and high temperatures.
  • Distribution/Characteristics: Especially serious in greenhouse cultivation. It also occurs outdoors in summer [1][4][5].

Thrips (Thrips tabaci, etc.) ​

  • Details of damage: Feeding and sucking the surface of flowers, young leaves, and fruits, silver-white patchy damage, and damage to the epidermis of fruits. Also virus-mediated.
  • Distribution/Characteristics: Occurs in both greenhouses and open fields. In Japan, it is one of the major pests of house cucumbers [2][6].

Leaf-eating and fruit-eating pests ​

Cucurbit beetles (Diabrotica undecimpunctata, etc.) ​

  • Details of damage:Adult insects damage the leaves (holes and missing food). The larvae feed on the roots, causing weakening and lodging of the plant. There is also direct damage to fruit.
  • Distribution/Characteristics: Extremely important in North America. In Japan, cucumber beetles (Aulacophora femoralis, etc.) are a problem in open fields [7][8].

Scarab beetle larva (Root feeding damage) ​

  • Details of damage: Feeding the roots underground, causing poor growth and withering of the plant. It is especially serious during the seedling stage.
  • Distribution/Characteristics: Occasionally seen in open field cultivation [8].

Spodoptera, etc. ​

  • Details of damage: Massive damage to leaves and fruits. Occurrence increases in the open summer season.
  • Distribution/Characteristics: Be careful in warm regions and tropical cropping types [3].

Major diseases (including white powder) ​

Powdery Mildew ​

  • Pathogen: Podosphaera xanthii, Erysiphe cichoracearum, etc.
  • Details of damage: White powdery sludge appears on leaves and stems. Decreased photosynthesis, early death, and reduced fruit quality. One of the most important diseases for both greenhouse and outdoor fields.
  • Conditions of occurrence: Epizootic in dry and warm environments. Proliferates due to dense planting and poor ventilation [1][9].

Downy Mildew ​

  • Details of damage: Yellow spots on leaves, gray-purple haze on the underside. Rapid leaf withering and significant yield reduction.
  • Distribution: Occurs in cool and humid conditions. It is a cautionary disease in Japan [9].
  • House cultivation: Aphids, spider mites, thrips, and powdery mildew are the main problems throughout the year [1][2][4].
  • Open field cultivation: Cucurbit beetles, armyworms, whiteflies (vector pests), etc.
  • Hot and dry period: Be careful of spider mites, aphids, and powdery mildew occurring at the same time.

References ​

[1] Cucumber pest control - NARO: https://www.naro.go.jp/laboratory/tarc/to-noken/
[2] Insect Pests of Cucumber - Ministry of Agriculture, Forestry and Fisheries: https://www.maff.go.jp/j/seisan/keiei/hozen/
[3] Insect Pests of Cucumber - University of Maryland Extension: https://extension.umd.edu/resource/insect-pests-cucumber
[4] Spider mite management in greenhouse cucumber: https://www.canr.msu.edu/news/spider_mite_management_in_greenhouse_cucumber
[5] Two-spotted spider mite in vegetables - NSW DPI: https://www.dpi.nsw.gov.au/agriculture/plants/vegetables/pests-diseases/spider-mite
[6] Thrips tabaci on cucumber - CABI: https://www.cabidigitallibrary.org/doi/10.1079/cabicompendium.54230
[7] Cucumber beetles - Purdue Extension: https://extension.entm.purdue.edu/publications/E-31/E-31.html
[8] Cucumber beetles control - National Rural Education Association: https://www.jaffc.or.jp/
[9] Powdery mildew of cucurbits - APSnet: https://www.apsnet.org/edcenter/disandpath/fungalasco/pdlessons/Pages/Cucurbits.aspx

In cucumber cultivation, early detection of these pests and diseases, cultivation environment management (ventilation, humidity, crop rotation), and an appropriate combination of biological and chemical control are the keys to stable production and quality maintenance.

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