Studies On Investigation And Control Of Major Pitaya Diseases In Guizhou Province

As a new tropical and subtropical fruit tree, pitaya (Hylocereus undatus Britt. & Rose) for integrating with fruits, flowers, vegetables, health care, and has a quite high economic value. In recent years, viewed from development of ecological and high-efficiency agriculture, and characteristic and fine fruit, more attentions are paid to research pitaya. It was found that the diseases occurred relatively lighter when scattered planted, but a bit more serious when centralized planted. According to the preliminary investigation, planting areas of pitaya in Guizhou province had harmful infection from many pathogenic bacteria, which seriously affected the growth of plants, even led to the death, so gave a great threaten to the production of pitaya. The investigation and identification of diseases in Guizhou pitaya and theirs occurrence regularity were studied in this paper to master some protective technologies and provide a theoretical basis for disease control of pitaya.Disease in pitaya mainly include stem blight (Mycosphaerella sp.( Phoma sp)), stem spot (Septogloeum sp), soft rot (Erwinia), black spot (Alternaria sp.), virus disease, physiological disease, chilling injury and so on, among which the first three kinds were the main pitaya disease according to the investigation during 2007 2008. Additional, the taking place symptom and regularity of the main three diseases in pitaya were made systematic investigation to further understand the key factors to lead disease and take effective measures to control disease.Agricultural measures should be raised primarily as the main control strategy, and chemical measures play a supporting but subsidiary role on the prevention and control of the three diseases. First, paying more attention to the eradication of primary infectious pathogen. Second, selecting resistant varieties, controlling-test with medicament should be carried out when necessary. Chemical control of stem blight and stem spot disease in pitaya should be combine screening of indoor fungicide with field control effect. In the process of trail on fungicide suppression of stem blight, 6 kinds of fungicides in high concentrations were found to have better inhibitory effect, among which, 50% Thiram WP was the best, and others successively were 50% Carbendazim·sulfur WP, 70% Thiophanate Methyl WP, 42%Kejunjing WP, 70% Mancozeb WP and 75% Chlorothalonil WP, followed by EC90 of 537μg/mL, 1259μg/mL, 1259μg/mL, 3162μg/mL, but 42% Kejunjing WP and 75% Chlorothalonil WP, followed by EC₉₀ of 4677μg/mL, 5843μg/mL were less effective. Correspondingly, based on the test of fungicide suppression of stem spot, 5 kinds of fungicides in high concentrations were found to have better inhibitory effect, among which, 42% Kejunjing WP was the best, and others successively were 50% Carbendazim WP, 50% Thiram WP, 70% Mancozeb WP and 70% Thiophanate Methyl WP, followed by EC90 of 1071.52μg/mL, 1412.54μg/mL, 4466.84μg/mL, 4677.35μg/mL and 8317.64μg/mL. According to the indoor test of pharmaceutical inhibition, some suitable fungicide and its concentration for the stem blight and stem spot diseases in pitaya had been selected to carry out the field controlling effect. Results showed that 50% Thiram WP with concentration of 400μg/mL and 500μg/mL or 50% Carbendazim·sulfur WP with concentration of 700μg/mL and 900μg/mL can all achieve the best control effect at the preliminary stage of stem blight disease in pitaya. Moreover, 42%Kejunjing WP with concentration of 500μg/mL had the best control effect at the preliminary stage of stem spot disease in pitaya. All of the Chemicals with different concentrations were carried out every seven days, for three times, and can be popularized and applied in production. Agricultural measures were usually taken to control stem rot disease in pitaya, which can effectively reduce propagation, transmission and spreading of the disease. Pruning in time and removing rotten position at the beginning of stem rot, then spraying fungicides for the wound, thus can also achieve a better control effect.