Studies On Identification And Field Control Of Chinese Hickory Dry Disease

Income from the Chinese hickory?Carya cathayensis Sarg?plantation contributes significantly to the local economy in the mountainous areas of Anhui and Zhejiang provinces.It is the main source of income for farmers in the region.Currently the Chinese hickory pest problems have become a bottleneck for further expanding of hickory plantations.A new fungal disease of the Chinese hickory,stem dry rot,was discovered in Ningguo,Anhui province recently.Ningguo is one of the main growing areas of the Chinese hickory.Published literatures showed that there are a few major diseases on the Chinese hickory,which include hickory leaf spot,stem blight,seedling root rot and canker diseases.Stem dry rot has never been reported previously.The disease usually occurs on the trunks,main branches.It starts with a small,nearly circular lesion and spreads slowly.In order to find a fungicide to control the disease effectively,a panel of fungicides was screened and two of them were selected for field trials.The pathogen of the disease was isolated and purified and its pathogenicity was confirmed following the Koch's postulates.The pathogen was identified based on the morphological characteristics and ribosomal internal transcribed spacer?rDNA-ITS?sequences.Below are a few key points of the results from this study.1.Identification of the pathogen of the Chinese hickory stem dry rot: The pathogen was identified as Fusarium solani based on the morphological characteristics and rDNA-ITS sequences and its pathogenicity was confirmed.The study of biological characteristics of the fungus showed that it can grow in the pH range of 4-9.5.The optimal pH for growth is pH7.The growth temperature ranges from 4 – 40°C and optimal at 25 °C.The fungus grows well on SDAY,1/4SDAY,PPDA and PDA media.The most suitable medium for the growth and sporulation of the fungus is PDA.2.Screening of fungicides for treatment of the Chinese hickory stem dry rot: 9 effective and low toxicity fungicides were selected for in vitro antifungal testing.The results showed that all of the nine fungicides had certain inhibitory effect on the mycelium growth.The Difenoconazole and Hymexazol?Lu Heng No.1?are the most effective with EC₅₀ at0.10 ug / mL and 0.38 ug / mL respectively.Fenaminosulf had poor inhibition on the fungus with EC₅₀ at 19.18 ug / mL.Therefore,The Difenoconazole and Hymexazol were used for field trials.3.Field trials of the Chinese hickory stem dry rot control with selected fungicides: Two fungicides selected based on laboratory in vitro test result were used for field trials.Four application methods were used,i.e.methods A-trunk drilling injection,method B-dressing with nonwoven fabric with fungicides after removal of lesion,method C-spraying and method D – combination of method A and methods B.The results showed that both Difenoconazole and Hymexazol had certain inhibitory effect on the lesion expansion.But different application methods showed great difference in the results.The most effective method is method D which showed efficacy at 85.4% and 87.9%respectively for Difenoconazole and Hymexazol,followed by method A with efficacy at74.4% and 80.2% respectively.The third is method B with efficacy at 52.0% and 57.4%;method C is not very effective and had efficacy at 30.1% and 36.5%.After comparing four kinds of control methods it is obvious that method showed the best result.