Causes and control methods of a small number of crooked, deformed pods in greenhouse kidney beans

    The kidney beans grown in greenhouses sometimes produce deformed pods, mostly appearing as a "hook," and analysis shows the following causes:

Kidney bean

    First, spraying with chemicals to which kidney beans are sensitive. Kidney beans are sensitive to chemicals containing mancozeb, zineb or diethofencarb; excessive application can easily bend the pods. Kidney beans are extremely sensitive to oxadixyl, which easily causes phytotoxicity and deformed pods. Some kidney beans also show phytotoxicity after spraying with copper preparations or thiophanate-methyl plus thiram, with mild cases causing bent pods and severe cases causing leaf and pod drop. When controlling diseases such as gray mold and sclerotinia, the safer chemicals for use on kidney beans are iprodione, procymidone, chlorothalonil, vinclozolin, iminoctadine and carbendazim. When using copper preparations to control bacterial diseases, the dosage should be halved. Chemicals containing mancozeb, zineb or diethofencarb should be used with caution or not at all, to prevent phytotoxicity that causes deformed kidney beans, affects yield and quality, and leads to unnecessary losses.

    Second, boron deficiency. With boron deficiency, kidney beans struggle to set pods; even if pods set, the flowers are large and the pods long and curved, with poor market quality. The solution is to spray 1200-fold Sule boron before flowering.

    Third, excessively high or low temperatures can cause bent pods. The most suitable temperature for kidney bean growth is 23-25°C during the day and 18°C at night, and the best temperature during the flowering period is 23°C. If daytime temperatures fall below 20°C or rise above 30°C, pod setting will be affected. At noon during the flowering period, be sure to check the temperature in the greenhouse and regulate it properly. In addition, to ensure that carbon dioxide enters the greenhouse early during the winter closed period and photosynthesis proceeds early, open the vents as early as possible one hour after sunrise in winter when temperature conditions allow, to increase the carbon dioxide concentration in the greenhouse and maintain normal photosynthesis.

    Fourth, adverse environmental effects. Soil that is too dry or waterlogged in the greenhouse easily causes newly set pods to develop what vegetable growers call a "hook." This is because overly dry or overly wet soil damages the root system, leading to weakened plants and affecting flowering and pod setting. To keep pods from bending, the root system must first be made to grow vigorously. Do not water before flowering. Watering should be based on soil moisture conditions, and after pods set, watering should be combined with fertilization. From transplanting to before flowering, water four times with light watering, generally about 20 cubic meters per mu, rather than flood irrigation, to avoid root rot and root damage.

    Fifth, excessive use of growth inhibitors. When vegetable growers spray excessive growth inhibitors on kidney beans that are growing vigorously but failing to set flowers, such pesticides as chlormequat and difenoconazole easily cause hooks to appear on kidney beans. Some vegetable growers, when spraying naphthaleneacetic acid to prevent pod drop, cause pod bending because the concentration is too high, and this should also draw our attention.

    Sixth, excessively high soil solution concentration, excessive chemical fertilizer application or saline-alkali soil can also cause deformed pods. In response, apply less chemical fertilizer and more humic acid fertilizers. After pods grow to 3-4 cm long, apply 30-60 jin of humic acid fertilizer per mu as a flush fertilizer to supplement nutrients, and by no means apply excessive chemical fertilizer, which raises the soil solution concentration and causes pods to bend. For growing kidney beans in saline-alkali soil, soilless cultivation is best, to avoid direct contact between the kidney bean root system and the saline-alkali soil, which affects root growth.