Identification and Control Methods of the Lingzhi Flat Bug
The flat bug Mezira membranacea branacea (Frab.) belongs to the order Hemiptera, family Aradidae. This insect was first discovered on log-cultivated lingzhi (Ganoderma lucidum) in Baoxi Township, Longquan City in 1994. In recent years, it has caused very serious damage in log-cultivated lingzhi production areas, with its range of damage expanding day by day, greatly affecting the yield and quality of log-cultivated lingzhi. The lingzhi flat bug is mainly distributed in Longquan, Zhejiang, China; Shaowu, Fujian, China; Nanning, Guangxi, China; Hainan Island, China; Taiwan, China; and Japan.
Damage characteristics: The flat bug sucks the sap from lingzhi mycelium and primordia, affecting mycelial growth. After lingzhi logs are damaged, the number of fruiting bodies produced decreases, the lingzhi individuals become smaller, and deformed lingzhi appear; in severe infestations, fruiting body formation is inhibited, reducing lingzhi yield and quality.
Morphological characteristics
Adult body length 9-12 mm, pronotum width 3.0-4.0 mm, abdomen width 3.4-4.5 mm. Body flattened, body color brown to black. Head extended forward, with the tip forked. Antennae protruding, 4 segments, the first segment relatively thick, the fourth segment shortest. The front half of the fourth segment is brown and densely covered with gray cilia. The rostrum is brown, relatively short, extending to the posterior margin of the open rostral groove. Compound eyes protruding, hemispherical. Pronotum nearly trapezoidal, with 4 irregular elevations on the front half, and the center of the posterior margin distinctly curved forward. Scutellum triangular. The two sides of the base of the forewings are parallel, and the wings are narrow and small. The forewings of males extend past the center of the seventh abdominal tergite, while those of females extend to the base of that segment; the veins of the membranous wing are distinctly raised. The lateral lobed angles of the seventh abdominal segment of females are horn-shaped; the posterior margin of the ninth abdominal segment is relatively flat and blunt, with its center slightly protruding. Males have a prominent central longitudinal ridge, and the abdominal spiracles are located on the ventral surface, far from the lateral margins.
Egg length 1.8-2.0 mm, resembling a grain of rice, milky white when first laid, semi-transparent, glossy; later turning orange-red, with red eye spots appearing. The front end is slightly larger than the rear end, and the eggshell surface has distinct 5-6 sided reticulate ridge patterns.
Nymphs have 5 instars in total. The 5th-instar nymph is light brown, elongated oval in shape, with the head protruding forward. Antennae 4-segmented, each segment sparsely covered with brown cilia; compound eyes red, relatively large; rostrum extending to the middle of the prosternum, scutellum raised upward, wing pads chestnut brown, extending to the dorsal surface of the first abdominal segment. The tubercles on the abdominal segments are arranged in 4 longitudinal rows, tubercle shapes and sizes varying, chestnut-colored; spiracles regularly arranged between the second longitudinal row on the outer side of the ventral surface; the center of the dorsal surface of the fourth abdominal segment has a relatively large brown raised protuberance, and the center of the dorsal surface of the fifth abdominal segment has a small brownish-red round spot. The thorax and abdomen are densely covered with small light brown dots formed by tubercles.
Occurrence pattern: The lingzhi flat bug has two generations per year in Zhejiang. Adults overwinter in the soil around and at the bottom of lingzhi logs, and can also overwinter under wood chips and bamboo chips closely attached to the soil surface inside lingzhi sheds. In late April of the following year, adults begin activity and mate. The peak oviposition period is from late May to early June. Adults can emerge during both day and night. In the early emergence stage, the body is pinkish-white with a slight reddish tint and basically immobile; after 4-5 hours the body begins to harden, the body color darkens, and finally becomes brown or black. They can mate multiple times, and eggs can be laid within 1 day after mating, but most begin laying eggs on the second day. The oviposition period is 6-12 days. Eggs are mostly laid in cracks in the log wood. Mid-June is the peak hatching period. Newly hatched nymphs cluster and attach to the bodies of adults or older nymphs, dispersing as the adults move; after the third instar they detach from the adults. From mid-to-late July to early August, most nymphs begin to emerge as first-generation adults. First-generation adults lay eggs from late July to mid-August, and second-generation adults appear from late September to mid-October. From late October to early November, adults successively enter the overwintering period. Adults have a death-feigning habit; they prefer shade and avoid light; they like to live in groups, with as many as more than 300 individuals clustering together; their flying ability is relatively weak, and on stuffy hot days, flying insects can be observed inside lingzhi sheds.
Control methods
(1) According to the overwintering habits of adults, before overwintering place some wood chips or bamboo chips around the lingzhi shed and surrounding field plots to attract adults for overwintering, then concentrate and eliminate them.
(2) Arrange new logs before the adult peak period, so that the first batch of lingzhi can be harvested before July and the second batch before early October, avoiding insect damage.
(3) Implement a crop rotation system, avoid continuous planting, and reduce insect damage.
(4) For chemical control, use 80% dichlorvos emulsifiable concentrate at 1000 times dilution plus 5.7% cyfluthrin emulsifiable concentrate at 2000 times dilution, or use 40% phoxim emulsifiable concentrate at 1000 times dilution plus 5.7% cyfluthrin emulsifiable concentrate at 2000 times dilution for drenching, with a spray liquid volume of 75 kg per cubic meter of logs. Alternatively, use the irrigation and spraying method: taking advantage of the habit of both adults and nymphs crawling upward out of the soil surface after encountering water, first irrigate to submerge the soil surface for 4-5 hours, then use spraying to kill them. Cover with plastic film promptly after spraying to improve control efficacy.
Commonly used pesticides: dichlorvos emulsifiable concentrate, cyfluthrin emulsifiable concentrate, phoxim emulsifiable concentrate.