Underground pests, particularly grubs, pose a major threat to agriculture and horticulture worldwide. These pests include the larvae of Grubs, wireworms, Gryllotalpa, Agrotis, and root maggots, which cause extensive crop damage by feeding on the roots and other underground parts of plants.
Controlling these pests is critical to maintaining crop health and preventing significant economic losses. Effective management requires understanding the biology and behavior of each pest and implementing targeted control measures.
Types of Underground Pests
Grubs
Wireworms
Gryllotalpa
Agrotis
Root Maggots
Grubs are the larvae of scarab beetles or golden tortoiseshells, commonly known as chicken moths and white earthworms. Its body is fat, round and simple, curved into a “C” shape, the skin is white or yellowish-white, and the body wall is soft and wrinkled. The head is large and round, reddish brown or yellowish brown, with symmetrical bristles on both sides of the head. Grubs have three pairs of thoracic legs, generally with longer hind feet, and an abdomen with 10 segments, the 10th called the pygidium (hip segment), which bears prickly hairs and is a subspecies characteristic.
The grub has a global distribution and lives in moist, loose, fertile soils, often camouflaging death for self-defense, and is omnivorous, preferring seeds, roots, tubers, tubers, and seedlings. According to the feeding nature is divided into phytophagous, coprophagous and saprophagous. Phytophagous grubs damage a wide range of crops and flowers and are worldwide underground pests, but some fecal-feeding species are ecologically beneficial.
Harm:
Larvae feed on the seeds, fibrous roots, nutrient roots and subterranean stem cortex of many plants, which can bite off the roots of seedlings, leading to seedling deficiency, seedling death, and in severe cases, seed destruction. Adults sometimes feed on leaves and tender stems.
Pharmaceutical control methods:
Soil treatment: before sowing or transplanting, use 10% diazinon granules 7.5 kg per hectare, mixed with 225-450 kg of fine soil and withdrawn on the bed soil or in the sowing furrow.
Irrigation: grub serious fields, with 80% Trichlorfon WP 800 times liquid irrigation roots, each plant irrigation 150 ~ 250 ml of liquid.
Spreading poisonous soil: from mid-June to mid- to late-July, use 3.75 kg of 50% phoxim emulsion per hectare mixed with 300 to 375 kg of fine soil to spread, and hoe shallowly into the soil.
Seed mixing: 0.1-0.15 kg of 45% phoxim emulsion per 50 kg of seed, diluted with 3.5-5 kg of water, sprayed on the seed, stirred and smothered in a heap for 5-10 hours, and then sown after the seed dries in the shade.
Adult pest control: in the early stage of adult pest infestation, use 45% malathion EC 2,000 times liquid or 40% dimethoate EC 800 times liquid spray, spraying once every 7 to 10 days.
Wireworms are the larvae of click beetles, which are elongated, yellow to reddish-brown in color and shiny in appearance, similar to mealworms. The length is usually between 1/4 and 1 1/2 inches and the width is about 1/8 inch. Different species are distinguished by the characteristics of the last segment of the body. Adults are brown or black “streamlined” beetles that make a clicking sound when turned over.
Wireworms feed on a wide variety of plants, including grasses (cereal crops such as corn), vegetables (such as beans, beets, cabbage, carrots, lettuce, onions, peas, potatoes, and turnips), and herbaceous ornamentals. They are especially common in areas such as old fields or grassy pastures, which are suitable for female kowtows to lay eggs.
Harm:
Larvae feed on seeds and seedlings, resulting in no or delayed germination of seeds and stunted or dead seedling growth, causing uneven plant thinning and seedling breakage.
Gnawing on the roots and underground stems of older plants, resulting in stunted roots, brown spots, and stunted growth and wilting of the above-ground parts of the plant.
It is more harmful to potatoes, digging and chiseling small, round tunnels in the potato tubers, making them unusable.
Pharmaceutical control methods:
Insecticides containing ingredients such as thiamethoxam or chlorantraniliprole can be used. When applying agents, follow the dosage and method on the product instructions to ensure control and avoid harm to the environment and crops.
Gryllotalpa are a group of ground-dwelling insects belonging to the Orthoptera: Gryllotalpidae. They have a pike-shaped body with fossorial legs that are specialized for underground digging. There are about 110 known species of Gryllotalpa worldwide, with different species varying in body size and distribution area.
The main hazards of Gryllotalpa include gnawing on seedlings and destroying the root system. They can bite off the rootstocks of seedlings, causing them to die and affecting the emergence and survival rates of crops. For example, in vegetable cultivation, Gryllotalpa may destroy the newly emerged seedlings in large quantities, resulting in the lack of seedlings and broken rows. At the same time, they dig tunnels in the soil, damaging the root systems of crops and affecting plant growth and development. The root systems of crops such as corn and wheat may be damaged by Gryllotalpa activity, reducing the ability to absorb nutrients and water.
The main methods of controlling Gryllotalpa are soil treatment and bait trapping. Before sowing, soil can be treated with agents such as phoxim and chlorpyrifos to kill Gryllotalpa larvae and adults in the soil. For example, the agents are mixed proportionally with fine soil, spread on the soil surface and then tilled. In addition, poisonous bait can be made by mixing fried wheat bran and bean cake with trichlorfon, etc., and then spreading it on the field in the evening to kill Gryllotalpa. mixing the bait with the chemicals according to the proportion and placing it in the place where Gryllotalpa often moves around has a significant effect.
Agrotis (Latin name: Agrotis ipsilon), commonly known as root cutter, is a polyphagous crop pest of the Lepidoptera nightshade family. Its morphological characteristics are as follows:
Eggs: hemispherical, 0.6 mm in diameter, creamy white when first laid, brownish before hatching.
Larvae: old mature larvae 37-50 mm long, yellowish brown to blackish brown; body surface densely covered with small black granular protuberances, with light-colored longitudinal bands on the dorsal surface; 2 dark brown longitudinal bands on the dorsal plate of the terminal abdominal segments.
Pupa: body length 18-24 mm, reddish brown to blackish brown; abdominal end with 1 pair of anal spines; male moth clasper end hypertrophied, phallus without antennal apparatus.
Adult: body length 16-23 mm, wingspan 42-54 mm; head, thorax and forewings brown or blackish gray, forewing anterior margin area darker, with kidney mark, annular mark and stick mark, outside the kidney mark there is a tip outward black wedge mark with the sub-marginal line of the inner two. black wedge mark with tip inward opposite submarginal line; dorsal surface of abdomen gray.
Hazard:
Noctuid moth larvae nibble on the leaves of crops, causing leaf mutilation, interfering with photosynthesis, and, in severe cases, causing plant death and reducing yields. For example, noctuid moth larvae will munch heavily on vegetable leaves, affecting quality and yield. Some noctuid moth species also attack fruits, stalks and other parts of the plant, affecting crop growth.
Pharmaceutical control methods:
Biological control: Spray control using Bacillus thuringiensis (Bt) preparation, which is relatively friendly to the environment.
Chemical control: Use chemical agents such as chlorantraniliprole and emamectin benzoate to spray in accordance with the specified concentration and method, but attention should be paid to the safety interval to avoid pesticide residues.
Root Maggots is a collective term for the larvae of several species of root maggot flies (Diptera: Anthomyiidae). They feed on the roots and bulbs of crops such as onions, carrots, and cabbage, resulting in stunted plant growth and yellowing of the leaves. The main symptom is wilting, especially during hot, dry weather. Small holes or channels appear in the infested roots, predisposing them to fungal and bacterial infections.
Common Species:
Kale seed fly: infests cabbage, cauliflower, turnips, and other cruciferous vegetables; adults have two dark bands on the prothorax.
Onion fly: attacks onions, green onions, leeks, etc., adults are slightly larger than the kale seed fly.
Harm:
Feeds on roots and underground stems, causing hollow rot.
Inhibits crop growth with dwarf plants and yellowing leaves.
In severe cases, it can cause the whole plant to die and the underground parts lose their food value.
Wounds are prone to cause other diseases.
Pharmaceutical control:
25% Thiamethoxam: for facility agriculture substrate cultivation, recommended concentration 2000 times liquid.
40% Phoxim: used for quinoa root maggot larval stage, surface spraying, 7 days control effect of 95.5%.
40% Chlorpyrifos: for quinoa root maggot control, 7 days control effect of 92.1%.
20% Dinotefuran: control of quinoa root maggot larvae, 7-day control effect of 76.1%.
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