บทคัดย่องานวิจัย

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Interaction and control of alternaria stem decay and blue mold in D'Anjou pears

Sitton, Jerry Webb.

Thesis of Ph.D., Department of Plant Pathology, Washington State University, Pullman, Washington. 1984. 95 pages.

1984

บทคัดย่อ

INTERACTION AND CONTROL OF ALTERNARIA STEM DECAY AND BLUE MOLD IN D'ANJOU PEARS.

Decay of stems of d'Anjou pears by Alternaria alternata is found in fruit treated with benomyl postharvest drench for control of Penicillium expansum and subsequently held in storage for prolonged periods.  Control of P.  expansum with benomyl favors the incidence of A.  alternata, which grows more slowly and is less competitive than P.  expansum at the osmotic potential (-22 bars) and temperature (near 0 C) conditions of pears in storage.  Prochloraz, chlorothalonil, iprodione, and triadimenol, combined with benomyl controlled both alternaria stem decay and blue mold on fruit treated and held for 6 or 7 months in cold storage.  The most effective control of both diseases, stem decay and blue mold, was obtained with 1000 (mu)g/ml prochloraz combined with 500 (mu)g/ml benomyl.  Reduction of linear growth of A.  alternata on potato dextrose agar amended with prochloraz was not correlated quantitatively with disease control.  Mycelial growth of A.  alternata was inhibited with 1.0 (mu)g/ml but 1000

  (mu)g/ml was required in the drench for disease control.  Winter Nelis pears are more resistant to alternaria stem decay than are d'Anjou, Bosc, Dawn, (Pyrus communis, respectively) or Pyrus serotina pears, but Winter (Pyrus communis) Nelis pears are susceptible to infection by P.  expansum.

 There was no evidence of significant interspecies antagonism due to antibiotics.  There was evidence that these fungi were able to coexist and that the use of benzimidazole shifted "the balance" from one favorable to P.  expansum to one favorable for the growth of A.  alternata in pear pedicels.

 P.  viridicatum series, a weak pear pathogen, was capable of producing substances in vitro which inhibited growth of A.  alternata.  This fungus was tolerant of benomyl at concentrations as high as 100 (mu)g/ml on agar plates.  Like A.  alternata, P.  viridicatum series may be favored by use of benomyl.