The most "curly" ginkgo pest in nature: the super small leaf roller

Ginkgo is a "living fossil" left over from 300 million years ago. It is a valuable economic forest tree species and an important garden greening tree species with important economic, ornamental, scientific research and ecological value. Ginkgo is a high-quality tree species with strong resistance to adversity and few diseases and pests. Since the mid-1980s, the ginkgo planting industry has developed rapidly, and foreign pests have also invaded. The ginkgo leaf roller is the most common and important pest of wild ginkgo. The rate of infestation has rapidly increased to 100%, and the average dead branch rate of fruiting branches is more than 30%, and in severe cases it is more than 60%.

Biological characteristics of Ginkgo leaf roller

Pammene ginkgoicola belongs to the order Lepidoptera, the suborder Heterocera, the family Pammene, and the subfamily Pammene. It occurs in all ginkgo producing areas in my country, mainly distributed in Guangxi, Zhejiang, Anhui, Jiangsu, Henan, Hubei and other provinces. The adult of the ginkgo leaf roller has a wingspan of about 12 mm and is dark brown in color. The eggs are flat and oval, with a smooth surface. They are orange-red when first laid, and dark yellow after 4 days. The mature larvae are 8-10 mm long, grayish white, with dark brown head, pronotum and anal plate. The pupa is 5-7 mm long, yellow when it first pupates, dark brown before emergence, and has black compound eyes.

The Ginkgo Leaf Roller has one generation per year and hibernates as pupae in the cracks of the bark. Generally, the adult emergence period is from late March to mid-April, the egg stage is from mid-April to early May, the larval damage period is from late April to late June, the larvae are in a dormant state after July, and pupate in mid-November.

Ginkgo leaf roller (picture from the Internet)

A ginkgo-specific pest that has both the skills of "boring" and "leaf rolling"

The Ginkgo Leaf Roller only harms Ginkgo biloba, and so far there have been no reports of other host plants. The insect harms the tender branches of Ginkgo biloba from April to July, and the damage is to bore into the short branches that bear fruits, and also bore into the new branches of the year. In the later stage, the larvae roll up the leaves to feed, causing the new branches of the year to turn yellow, burn, and fall off, and the leaves and young fruits to die and fall off, seriously affecting the growth of Ginkgo biloba and the landscape effect.

The occurrence of Ginkgo leaf roller pests is closely related to external environmental conditions. Old trees with poor tree vigor are more susceptible to damage, because leaf rollers prefer light and fear shade, so the damage at the edge of the forest is more serious than in the forest. Female trees are more serious than male trees; trees with sparse density on both sides of the road are more seriously affected by insects than trees with dense density in the village.

Damage, larvae and pupae of the Ginkgo leaf roller on Ginkgo leaves (Picture from the Internet)

Control of Ginkgo Leaf Roller

Manual control: Manually cut off the damaged branches and burn them to eliminate the larvae in the branches. Remove the damaged branches, and cut off the branches that are obviously withered in time and burn them in a concentrated manner to kill the larvae.

Strengthen cultivation management: apply fertilizers rationally and enhance tree resistance to reduce the extent of damage caused by the insect.

Chemical control: During the peak period of adult emergence, spray the tree trunks with a mixture of 250 times of 50% fenitrothion EC and 500 times of 2.5% cypermethrin EC in a ratio of 1:1. During the period of damage by the ginkgo leaf roller, the young larvae should be eliminated. Spray the affected branches with a mixture of 800 times of 80% dichlorvos EC or 800-1000 times of 90% trichlorfon powder and 80% dichlorvos EC (1:1), or 800 times of 80% dichlorvos EC and 1000 times of 40% oxydemeton-methyl EC, which has a better effect. According to the habit of mature larvae to move to the bark for dormancy, at the end of May or the beginning of June, spray with 2500 times diluted 25% cypermethrin emulsifiable concentrate, or use 1 part of 25% cypermethrin emulsifiable concentrate and 10% cypermethrin emulsifiable concentrate, mixed with 20 parts of diesel respectively, and apply it on the base of the trunk and 4 cm on the branches. The mortality rate for old larvae can reach over 90%.

Biological control: Make full use of and protect the natural enemies and pathogenic microorganisms of the Ginkgo leafroller, especially Beauveria bassiana, ladybugs and spiders.

Author: Luo Mingdan (graduate student of School of Life Sciences, Hubei University)

Scientific review: Xu Letian (Professor and doctoral supervisor at Hubei University)

Planning: Zhao Qingjian, Wu Yuetong