Small ground tiger, scientific name Agrotis ypsilon (Rottemberg) Lepidoptera, noctiaceae. Also known as soil silkworm, ground silkworm, black soil silkworm, black silkworm. Synonymous Noctua ypsilon. Distributed throughout the country.
1. Harmful characteristics
The larvae bite off the stems of the vegetable seedlings near the ground, causing the entire plant to die, causing the lack of seedlings to break the ridge, and even destroy the seeds in serious cases. It can also be drilled into the fruit of eggplant and pepper, or the leaf bulbs of cabbage and kale, which affects the quality. Second, morphological characteristics
Adults: 16 to 23 mm long, 42 to 54 mm wingspan, dark brown body. The inner and outer horizontal lines are double-line black and wavy. There is 1 kidney-shaped spot and 1 ring-shaped spot near the middle chamber of the forewing. The kidney-shaped plaque has 1 distinct black triangular sword-like stripe on the outside, with the tip outward, and 2 black sword-like stripes with the tip inwards within the sub-outer margin line, and the three-striped sword end is opposite. The hindwings are off-white and the abdomen is grey.
Male adult morphology
Female adult morphology
Egg: Hemispherical, bottom diameter about 0. 5 mm, height 0. 3 mm, the surface has a longitudinal and transverse uplift line. It is milky white at first birth, then yellowish, and pale grayish purple near hatching, with black spots on the top of the egg.
Larvae: Mature larvae are 42 to 47 mm long, with a yellowish-brown head and grayish-brown body. The back of the body is rough, covered with cracked wrinkles and tiny black particles. There are 2 pairs of hairy flakes on the back of each of the 1st to 8th segments of the abdomen, arranged in a trapezoidal arrangement, and the anterior pair is smaller. The hips are yellowish brown with 2 dark brown longitudinal bands.
Larval morphology
Pupae: 18 to 24 mm long, russet brown, shiny. The dorsal anterior margin of the 5th to 7th segment of the abdomen is dark brown, and each consists of a column of small black dots. The terminal is black with a pair of gluteal spines and is bifurcated.
Pupal morphology
Third, life habits
(1) Adult insects: adults are nocturnal, mating and laying eggs, and the eggs are laid on short weeds below 5 cm, especially on the leaf back or young stem close to the ground. Adults have a strong tendency towards black light and sweet and sour wine.
(2) Larvae: larvae total 6 years old, before the 3rd instar in the ground, weeds or host larvae parts of feeding, for little harm; after 3 years of age lurking in the topsoil during the day, come out at night to harm, agile movements, sexual cruelty, cannibalism. The old mature larvae have a suspended animation habit and are frightened into a ring.
(3) Development: Under the condition that the average daily temperature is about 20 °C and the optimal water content of the soil is 15% to 20%, the development period of eggs, larvae and pupae is 5 to 6 days, 30 to 34 days, and 18 to 22 days, respectively. Pupal development calendar 12— It takes 18 days, and the overwintering pupae last up to 150 days. The lifespan of female moths is 15 to 17 days, and the lifespan of male moths is 8 to 12 days. (4) Hazards: Newly hatched larvae often cluster on the heart leaf or leaf back of the seedling to take it, and bite the leaf into small gaps or mesh holes. After the 3rd instar, the larvae bite off the stems of the vegetable seedlings near the ground, and often drag the broken seedlings into the hole.
Fourth, the occurrence factors
(1) Generations occur. Due to the influence of temperature, the annual generation of algebra varies from north to south, 2 generations in Heilongjiang, 3 to 4 generations in Beijing, 5 generations in Anhui and Jiangsu, and 6 generations in Fuzhou.
(2) Overwintering. In the Yangtze River Basin, it can overwinter with old mature larvae, pupae and adult insects; in Guangdong, Guangxi and Yunnan, it breeds all year round, and there is no overwintering phenomenon.
(4) Environmental factors. Prefer warm and humid conditions, the most suitable development temperature zone is 13 ~ 25 ° C, in rivers and lakes or low-lying waterlogging, rainy and perennial irrigation areas, especially in the early spring vegetable fields and periphery of the weeds, can provide spawning places; honey source plants, can provide supplementary nutrition for adult insects, will form a larger source of insects, serious occurrence.
(5) Soil conditions: loose soil, good agglobulous structure, strong water retention loam, clay loam, sand loam are suitable for the occurrence of small land tigers.
Fifth, prevention and control methods
(1) Booby-trapping adult insects: Using the tendency of small land tigers to light, the field is installed with frequent vibration insecticidal lamps or black light lamps to trap and kill adult insects; pots or other utensils equipped with sweet and sour booby traps can also be placed in the field to trap and kill adult small ground tigers. Preparation method of sweet and sour liquid: 6 parts of sugar, 3 parts of vinegar, 1 part of white wine, 10 parts of water, 1 part of 90% of enemy insect crystals, mix well, and set during the adult occurrence period. Some fermented and sour foods, such as sweet potatoes, carrots, rotten fruits, etc., can also be booby-trapped to kill adult insects.
(2) Pre-sowing agent seed mixing: There are many optional seed mixing agents, such as 48% chlorpyrifos emulsion can be used to dilute the seed with water according to 0.3% to 0.5% of the seed amount. Or 18% fipronil chlorpyrifos microcapsule suspension at 1% of the seed amount, diluted with water. It can control a variety of underground pests, add some systemic insecticides, and can be treated concurrently.
(3) Before the vegetable seedlings are colonized, select the gray vegetables, thorny vegetables, if you sell vegetables, small spiny flowers, Bai Ji, Mu Zi, QingYi, White Grass, Goose Grass and other weeds that the tigers like to eat, and then artificially catch or mix them into the potion poison.
(4) Clean the countryside: Before seedlings and colonization in early spring, remove the vegetable field and the surrounding weeds, and when the weeds are cleared, shovel off the soil layer on the sunny surface of the field stem by about 3 cm to prevent the adult tigers from laying eggs.
(5) Artificial capture: In the early morning, around the affected seedlings, find the latent larvae, catch them every day, and insist on 10-15 days.
(6) Poison bait booby trap: After sowing, it is sprinkled between rows or plants. Bait preparation method: (1) bean cake (wheat bran) poison bait: bean cake (wheat bran) 20-25 kg, crushed, sieved into a powder, stir-fried evenly mixed with 40% octyl thiophosphorus emulsion 0.5 kg, pesticide can be diluted with water and sprayed into the stirring, to bean cake (wheat bran) powder moistened as well, and then according to the amount of 4-5 kg per acre sprinkled around the seedlings.
(7) Chemical control: Ground tiger 1— The poor resistance of the 3-instar larval stage and exposure to the host plant or the ground are the appropriate period for drug control. Check early in the morning every other day, if you find that the heart leaf is damaged or the leaf has small holes, spray it in time. Use 2.5% high-efficiency cypermethrin water emulsion 15 to 20 grams per mu, or 4% perchloromethyl salt microemulsion 40 to 45 grams /mu, and add 45 kg of water to the ridge spray for prevention and control.