Identification and Control Methods of Diomea cremata

Diomea cremata Butler belongs to the family Noctuidae of the order Lepidoptera. It is one of the looper caterpillars and is one of the important pests damaging edible fungi such as lingzhi (Ganoderma lucidum), oyster mushrooms and wood ear fungus, and it occurs fairly commonly in China.

The damage is characterized mainly by feeding on the lingzhi cap and flesh, leaving curved tunnels at the damaged sites. It also leaves notched holes on the fruiting bodies, reducing the commercial value of lingzhi.

Morphological characteristics

The adult has a body length of 11 mm and a wingspan of 25-26 mm. The male is dark purplish brown, and the head, thorax and the dorsum of abdominal segments 1-2 all bear thick, dense tufts of scales. The antennae are filiform; the labial palps are grayish black and curved upward, with the basal segment relatively small, the second segment very large, and the third segment tiny, with its base and tip white. The forewings are purplish black with a glossy sheen; the base is light black; the basal transverse line is yellowish white and curved outward; the median transverse line is black and curved outward at the front-middle part; the reniform stigma is black, curved inward and shaped like the figure "3"; the front end of the outer marginal line of the forewings and hindwings is a yellowish brown spot, followed by a row of small white dots arranged in an arc; the posterior end of the outer margin of the hindwings merges into a white curved marking. The female is dark brown, with the forewings blackish brown.

The egg is 0.5 mm long and 0.8 mm in transverse diameter, round and green, with more than 40 raised longitudinal ridges on the surface, and more than 20 fine, dense transverse ridges connecting the longitudinal ridges.

Larva: the larva has 5 instars in total; the final-instar larva is 25-30 mm long, with a blackish brown head and a cylindrical abdomen with obvious constrictions between segments; the dorsal midline is dark green, and white twisted line markings are scattered longitudinally along the dorsum. The hair plates on each segment vary in size and are brownish yellow with milky white surroundings. There are 3 pairs of prolegs on abdominal segments 5, 6 and 10, with the crochets arranged in a single row, uniordinal mesoseries.

Pupa: body length 11-13 mm, with 2 pairs of short spines at the posterior end of the abdomen.

Occurrence pattern: Diomea cremata has 5-6 generations a year in the south, mainly overwintering as pupae, usually emerging as adults in mid-April, with a full generation lasting about one month. The adults are attracted to sugar-vinegar bait and pollen; the female lays eggs on the third day after emergence, with the largest number of eggs laid on the fourth and fifth days, scattering the eggs at night or in the morning on the surface of the fruiting bodies and the substrate. The suitable growth temperature for this insect is 20-30°C; the egg stage is 5-6 days, the larval stage 11-15 days, the pupal stage 8-12 days, and the adult lifespan 3-13 days. Older larvae move slowly and have the habit of making cocoons and hanging; the larvae can still be active in November, and from late October to early November the mature larvae gradually pupate and enter the overwintering period.

Control methods

(1) Strengthen cultivation management: install screen doors and screen windows in the mushroom house to prevent adults from entering, improve environmental sanitation, and collectively remove waste and weeds around the mushroom house to reduce the source of the insects.

(2) After the last crop of edible fungi is harvested, the insects remaining in the substrate should be killed promptly to reduce pest damage.

(3) Taking advantage of the slow movement and cocoon-hanging habit of older larvae, they can be captured and removed manually to reduce the insect population density.

(4) Chemical control: when the pest breaks out in large numbers, after harvesting the mushrooms, spray the substrate surface, cultivation racks, etc. with a 5000-8000-fold dilution of 20% fenvalerate emulsion or other pyrethroid pesticides.

Commonly used pesticide: fenvalerate emulsion.