Effective control methods for leaf beetle pests on licorice

The main species of leaf beetles harming licorice include Diorhabda tarsalis, Pynrrhalta aenescens, Monolepta quadrigutdata, Diorhabda rybakowi, Ceytra sp., Colasposoma dauricum, Coptocephala asiatica, Basilepta fulvipes, etc. Since both the adults and larvae of leaf beetles voraciously consume licorice leaves, the damage is severe, and in affected fields whole patches of licorice leaves are often completely stripped off.

Diorhabda tarsalis is currently a major pest of licorice. In the northwest region of China, it produces three generations per year, overwinters as adults, and begins activity the following year when the average temperature reaches 10-15°C. The larvae have 4 instars and feed on licorice leaves. Adults and larvae occur overlapping, and when the damage is severe only stems and leaf veins remain; artificially planted licorice dies completely in the same year or the following year of infestation.

Control method: When a high insect population density is found in May-June (overwintering insects), pesticide should be sprayed promptly for one control application. 3% jiadi powder or 2.5% trichlorfon powder can be used, with about 2.5 kg per mu. Alternatively, during the peak occurrence period, 2.5% deltamethrin at 3000-5000 times dilution can be used. Before overwintering, measures such as clearing field debris and fallen leaves before winter and irrigation before winter can be carried out to reduce the overwintering survival rate.

(3) Control of licorice seed pests. The main licorice seed pests include Bruchidius ptilinoides, Bruchophagus glycyrrhizae, etc., which can cause considerable damage. The former mainly causes damage during storage, while the latter mainly causes damage in the field.

Bruchidius ptilinoides produces one generation per year, overwinters as larvae inside licorice seeds, and begins emergence in late May. It mainly feeds on licorice seeds during storage, and adults can also feed on licorice leaves. For seeds not treated that year, the infestation rate after overwintering reaches over 35%, and after two years of storage it reaches 77.4%.

Control methods should focus on the pod-setting stage and the period after licorice seed pods are harvested, threshed and stored in the warehouse.