柑橘黄龙病田间防控模式研究

Study on Field Control Model of Citrus Huanglongbing

为明确柑橘黄龙病(Huanglongbing,HLB)防控“三项”措施的有效性与可持续效应,通过建立HLB田间传播模型、病树砍除模型、木虱防治模型,据此理论进行解析和验证试验。结果表明,HLB始盛期拐点为发病率HLB=21.1%,建议HLB_(0)≥20.0%作为毁园临界预警。相对封闭橘园理论推算病树清除率下限为0.80,连续3年清除病树可使黄龙病初始发病率HLB_(0)=20.0%、传染率IR=1.0的果园实现低风险栽培(HLB<1.0%),其代价为累计病株砍伐率∑Cut≤25.0%。经仙游县2例果园,持续4年的试验验证,与理论推演基本相符。在敞开式橘园,当周边相邻背景果园面积S1远大于目标园面积S2(以下序号同义),且HLB_(1)>HLB_(2)时,目标果园受周边HLB高危入侵,维持橘园需要每年承担至少△HLB2(△HLB2≥IR1·HLB1)的损失,且HLB_(2)不收敛,即每年需承担同等砍树、补苗代价;当HLB_(1)>>HLB_(2)时,则要求增加病株消除率CR_(2)负荷,从而推高成本;若HLB_(1)<HLB_(2)时,目标园黄龙病向外扩散,HLB弃园属于此类情况;若目标园更替周期30年与及时补苗,则周边橘园安全阈值HLB_(1)≈3.0%。由HLB防控核心范式CR(1+IR)>IR推演dCR/dIR>1/(1+IR)^(2),表明清除病树比全园泛杀木虱更能有效的降低传染率,尤其在烈性传染时,应首选砍除病树来抑制疫情。无病苗对防范HLB仅具时效性,HLB入侵概率与栽培年限成正比。因此,在确保橘园常规病虫害防治即病、虫斑果率<5.0%条件下,持续清除HLB病树为控制疫情最经济与有效的方法,推荐将清除HLB列为冬季清园的制度化必备操作。在遇田间HLB识别疑难时推崇严苛“有病推定”。

In order to determine the effectiveness and sustainable effect of the three measures for the prevention and control of citrus huanglongbing,HLB field transmission model,infected tree cutting model and citrus psyllid control model were established.The effectiveness and sustainable effect were evaluated and verified based on the above models.The results showed that the incidence rate of HLB was 21.1%at the inflection point of the start peak period,so it is recommended that incidence rate of HLB_(0) greater than or equal to 20.0% could be used as a critical warning for the destruction of the orchard.In relatively closed citrus orchard,it was theoretically estimated that the lower limit of diseased tree removal rate was 0.80,and low-risk cultivation(incidence rate of HLB<1.0%)was realized in the orchard where the initial incidence rate was 20.0% and the infection rate IR=1.0 after the removal of diseased trees for 3 consecutive years.At the same time,the cutting rate of diseased plants was less than 25.0%.The test results of two orchards in Xianyou County as examples for 4 consecutive years have been verified,and the results are basically consistent with the theoretical deduction.In an open citrus orchard,when the area S1 of the surrounding adjacent background orchard was much larger than the area of the target orchard S2(the following serial numbers are synonymous),and HLB_(1)>HLB_(2),the target orchard was invaded by the surrounding HLB at high risk,and maintaining the citrus orchard needs to bear at least △HLB_(2)(△HLB_(2)≥IR1·HLB_(1))loss every year,and HLB_(2) does not converge,that is,the same cost of cutting trees and replanting of seedlings has to be borne every year.When HLB_(1)>>HLB_(2),CR2 load was required to increase,thereby improved costs.If HLB_(1)<HLB_(2),the disease of the target garden spreads out,and abandoned orchard fell into this category.If the replacement cycle of the target garden was 30 years and the seedlings can be replanted in time,the safety threshold of the incidence of Huanglongbing in the surrounding citrus orchards was 3.0%.Deduced from the core paradigm of HLB prevention and control CR(1+IR)>IR,dCR/dIR>1/(1+IR)^(2) showed that removing diseased trees was more effective in reducing the infection rate than killing psyllids in the whole orchard.Especially in severe cases,the first choice should be to cut down diseased trees to curb the epidemic.Disease-free seedlings are only time-sensitive to prevent HLB,and the probability of HLB invasion was directly proportional to the years of cultivation.Therefore,under the condition of ensuring that the rate of disease and spotted fruit is less than 5.0% for conventional pest control in citrus orchards,continuous removal of HLB diseased trees is the most economical and effective way to control the epidemic.It is recommended that continuous removal of diseased tree is a necessary operation when clearing the orchard in winter.Strict“presumption of disease”is recommended when encountering difficulties in identifying HLB in the field.