Pacific Pests, Pathogens, Weeds & Pesticides - Online edition

Pacific Pests, Pathogens, Weeds & Pesticides

Watermelon gummy stem blight (007)

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Photo 1. The large black spots are typical of gummy stem blight, Didymella bryoniae, on the leaves. Notice the concentration of the spots at the margins of the leaf where water stays for longer. Some of the spots have joined together.

Photo 2. This is typical of the defoliation that occurs with gummy stem blight infection, making it a serious disease. Leaves go yellow, collapse and die when they have only a few spots. The older leaves die first.

Diagram. Life-cycle of gummy stem blight, Didymella bryoniae.

Samari

  • Iu save faendem olova long wol long wata melon, cantaloupe melon and kiukamba (lukim Fact sheet no. 201). Hemi wanfala impoten siknis long olketa melon.
  • Siki ia hemi babae stat olsem smol mak wea kuiktaem grou go go hemi biki. Lif babae isi isi senis go long blak an skuis ap an dae. Olketa karekil an mak long vaen babae garem gummy (sticky) likuid.
  • Spred long win an ren wea muvum spoa from oketa lif go long nara lif or plant.
  • Lokol kontrol: nesari mas stap farawe from gaden, u mas kukim graon and eni ting u usim fo nesari, sekem gut olketa bebi melon blong u long nesari fo eni mak blong siknis an pulum aot if iu faendem. Lusim old gaden fo falo kasem 3 ias befo u kam baek an no plandem melon kolsap long gaden wea garem sikinis. Hemi impoten for iu mas bonem or berem everi lif an rop blong melon bihaen iu havest.
  • Kemikol Kontrol: coppers, mancozeb, or chlorothalonil afta 7 – 10 fala dei folom weda.

Komon nem: Gummy stem blight

Saentifik nem: Stagonosporopsis cucurbitacearum; (fastaem olketa kolem long Didymella bryoniae). Narafala nem blong hem tu, Phoma cucurbitacearum or Ascochyta cucumis, wea hemi asexual. Iu save faendem Phoma an Ascochyta long lif blong olketa melon long gaden long spoa wea hem stap long blak samting ontop lif olketa kolem ‘pycnidia’. U save lukim lo ae nating nomoa.

Photo 3. Gummy stem blight infection, Didymella bryoniae, on a seedling. It is just possible to see the black dots that contain the spores in the centre of the spot. Infection of seedlings in the nursery is a major threat to watermelon production as it means the fungus is taken to the field and early infection and spread is guaranteed.

Photo 4. Checking in the nursery for infections of gummy stem blight, Didymella bryoniae, on seedlings of watermelon. This should be done at least twice a week. If infections are found, the plants should be removed and burnt. Notice that the nursery is high above ground.

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