Control Of Major Pre-and Post Harvest Diseases With Azoxystrobin On Muskmelons(cv.Yindi)

Effects of AZX on major pre- and postharvest diseases of muskmelons (Cucumis melo L. cv.Yindi) were studied in this paper. AZX at 50,100,200 and 400mg/l were sprayed before harvest, respectively. The chemical was used for 3 times at flowering period, 7days after flowering and net formed stage, for 4 times at flowering period, 7days after flowering, 20days after flowering, and net formed stage. The results showed that AZX effectively inhibited the downy mildews and powdery mildews (caused by Plasmopora viticola and Uncinula necator, respectively) of melon leaves, reduced the latent infection rate of fruit, and controled Alternaria, Fusarium and pink rots of fruit (caused by Alternaria alternata, Fusarium sp. and Trichotethium roseum, respectively). AZX at 400mg/l with 4 time sprays had the most effective control on these pre-and postharvest diseases. AZX at 50,100,200 and 400mg/l significantly controled development of Fusarium and pink rots, respectively. AZX at 100mg/l showed the best control for both rots. Dip temperature and time had some effects on the control of Fusarium and pink rots. The treatments at 50癈 with 2min had better control than that at room temperature. AZX treatments pre- or post inoculation were compared. The treatments post-inoculation showed better control on Fasarim and pink rots than that of pre-inoculation. The longer of the period between AZX treatment and inoculation of pathogens, the weaker of the control effect. In vitro tests indicated imazalil had synergism action on AZX, but GA3 had no the action. However, with inoculated fruit both GA3 and imazalil showed synergism action on AZX. Treated fruits with 100mg/l AZX stored at 8 ± 1℃ had less decay. Both firmness and TSS were higher in treated fruit than that of untreated ones duing storage. Peroxidase (POD) and catalase (CAT) activities were increasesed in treated fruit compared to the control. The fruit treated at l00mg/L had higer POD and CAT activities than the treatments with 50mg/l and 200mg/l. AZX significantly inhibited spore germinationof Fusarium sp. AZX at 12.5-400mg/l effectively inhibited the mycelial growth of Fusarium sp and A.alternata in vitro. AZX caused some morphological changes of the hyphae from 12.5mg/l. The hyphae showed swelled, twisted and deformed, breakdown of chlamydospore. AZX in peel degraded quickly during 7 days of storage, and the residue level of three treatments at 100, 200, 400mg/l were low than lmg/1. AZX in flesh kept low during 14 days storage and the residue level was 0.035mg/kg in flesh of the treated fruit at 400mg/l, which is far below the tolerance level (2mg/kg) fixed by EPA in United States for bananas and in Italy for tomatoes and grapes.