山楂果实日烧病又称日灼病,是山楂果实遇高温、曝晒而引起的一种生理性病害,其症状表现为果实向阳面组织局部坏死,轻者呈水烫状褐色斑,以后失水,凹陷形成边缘不整齐的黑褐色病斑,影响果品质量;严重者造成大量落果,可减产35％以上。该病5月下旬至7月中旬均可发生,但以6月上中旬最为严重。不同山楂品种抗日烧能力不同,据调查:面楂抗日烧能力最强,小锦球次之,大金星最差。高温、干旱是该病发生的主要原因。6月上、中旬迅速膨大的山楂幼果表层组织抗逆性较差,对水份的需求异常敏感,若遇32℃以上的高温天气,经中午2—3小时的烈日曝晒,加之土壤干旱,水分供应不足,幼果阳面组织过度失水,从而导致组织变褐坏死。赤霉素(九二0)的使用与该病发生密切相关。近几年,盛花期喷施赤霉素已成为提高山楂座果率 Hawthorn fruit day burn disease, also known as sunburn, hawthorn fruit encountered high temperature, exposure and a physiological disease caused by the symptoms showed the sun to the surface tissue of the local necrosis, the light was brown water stains, after dehydration , The formation of uneven edge dark brown spots, affecting the quality of fruit; serious cases caused by a large number of fruit drop, yield can be reduced by 35%. The disease can occur from late May to mid July, but the most serious in mid-June. Different hawthorn varieties have different anti-Japanese burning abilities, according to the investigation: the hawthorn has the strongest anti-Japanese burning ability, the smaller Jinqiu ball and the worst Venus Star. High temperature, drought is the main reason for the disease. In June, the rapid growth of middle and late young hawthorn surface tissue resistance is poor, the demand for water is extremely sensitive, if the case of high temperature above 32 ℃, 2-3 hours at noon sun exposure, combined with soil drought, Insufficient water supply, young fruit Yang surface tissue excessive water loss, resulting in tissue browning necrosis. The use of gibberellin (Ji’ao 0) is closely related to the disease. In recent years, full bloom flowering gibberellin has become a hawthorn fruit rate