Beneficial Insect Species Have Been Used in the Production of Green, Clean, Safe Vegetables.
Using Beneficial Insects to Increase Safe Vegetable Yields
Currently, many types of green vegetables sold on the market contain residues of pesticides, which significantly affects consumer health.
The production of clean and safe vegetables in urban agriculture has become a pressing societal need in the urbanization process. Apart from the health protection aspect for the community, it also has significant economic and scientific implications as it aims toward sustainable agriculture. Research into utilizing natural enemies for effective pest control is an important direction in developing biological methods. This is also the main approach of integrated pest management and a crucial task for sustainable agricultural development.
Safe Vegetable Production
In the Hanoi area, including Ha Tay province, Me Linh district, Vinh Phuc, and four communes in Luong Son district, Hoa Binh, many regions have emerged focusing on safe vegetable production. Notably, greenhouse vegetable production models are being expanded and developed, such as the safe vegetable models grown in greenhouses in Dong Anh, Gia Lam, and Hoang Mai, as well as the vegetable cultivation area in Kim An and Linh Nam. However, in the cultivation of safe vegetables within greenhouses, pest control measures still employ methods similar to those used in open fields, leading to the abuse and increased usage of pesticides, chemical fertilizers, and growth stimulants.
Types of Beneficial Insects
According to the Plant Protection Department, in 2010, 28.3% of vegetable samples had pesticide residues exceeding the maximum allowable limits, 78.75% had lead levels above permissible limits, 50.02% had nitrate levels exceeding regulations, 67.85% contained E. coli, and 96.42% contained coliform bacteria. In recent years, research and utilization of insect resources with economic value on vegetable crops have been conducted and achieved many results. However, these studies have only been performed on vegetables grown in open fields, with no research conducted in the concentrated safe vegetable production areas within greenhouses, especially studies on pest species, their natural enemies, and biological pest control measures for greenhouse vegetables to support safe vegetable production following Good Agricultural Practices (GAP) instead of traditional field methods.
Contributing to safe vegetable production in the GAP direction, providing safe vegetable products for Hanoi and surrounding urban areas, the project “Research on the Species Composition, Development of Pest Insects, Their Natural Enemies, and Some Biological Control Measures Against Vegetable Pests for Safe Vegetable Production in Greenhouses at Several Points in Hanoi”, led by Assoc. Prof. Dr. Truong Xuan Lam from the Institute of Ecology and Biological Resources, Vietnam Academy of Science and Technology, has been implemented and yielded positive results. The project delves into analyzing the composition of pest insect species and their natural enemies on cruciferous vegetables grown in greenhouses, as well as the occurrence and development of some common species. Consequently, it involves the breeding and release of some predatory and parasitic species to control pests on cruciferous vegetables in greenhouses.
On cruciferous vegetables in Hanoi, 28 pest species from 16 families and 7 orders, along with 41 species of parasitic and predatory insects from 18 families and 6 orders, have been recorded. Among these 28 pest species, five are commonly found and pose significant harm, including the diamondback moth (Spodoptera litura), cabbage white butterfly (Pieris rapae), cabbage looper (Plutella xylostella), gray aphid (Brevicoryne brassicae), and striped flea beetle (Phyllotreta striolata). Among the 41 species of parasitic and predatory insects, eight are prevalent and found both inside and outside the greenhouses, including the red ladybug (Micraspis discolor), six-spotted ladybug (Menochilus sexmaculatus), two-spotted ladybug (Lemnia biplagiata), Japanese ladybug (Propylea japonica), three-striped rove beetle (Paederus fuscipes), brown-banded hoverfly (Episyrphus balteatus), white cocoon parasitic wasp (Apanteles sp.), and aphid parasitic wasp (Diaeretiella rapae).
Study of the Development of Common Species on Greenhouse Vegetables
During two years of investigation (2011 – 2012) on cabbage and kohlrabi, the population density of five pest species peaked twice in the greenhouse environment: the diamondback moth peaked in May and November, the cabbage white butterfly peaked in February and May, the cabbage looper peaked in January and May, the striped flea beetle peaked in May and December, and the gray aphid peaked in January and May. The density of predatory species was very low in the greenhouse, with ladybug groups peaking twice in May and December. Other groups peaked once, including predatory stink bugs peaking in June, predatory rove beetles peaking in October, predatory beetles peaking in February, and the three-striped rove beetle peaking in April. Aphid parasitic wasps played a minimal role in controlling aphid populations, with parasitism rates peaking in February.
In greenhouse-grown vegetables, the relationship between predatory stink bugs, rove beetles, three-striped rove beetles, ground beetles, and ladybugs with the main pest species (diamondback moth, cabbage white butterfly, cabbage looper, and gray aphid) is low and has little role in suppressing the populations of these pests. The farming season, fertilization regime, and vegetable care techniques differ in greenhouses compared to outside, affecting the average density of diamondback moths, cabbage white butterflies, striped flea beetles, predatory ladybugs, predatory stink bugs, three-striped rove beetles, and predatory beetles on cabbage and kohlrabi. In greenhouses, the density of predatory stink bugs, ground beetles, three-striped rove beetles, and ladybugs in fields treated with pesticides is very low, and in the treatment groups with four or more pesticide applications per season, predatory species were not observed. Even with two pesticide applications per season in greenhouses, it similarly affected predatory species as three applications would in open fields.
Results of Breeding Red-Eyed Wasps and Other Key Predatory Insects in the Laboratory
The project team has successfully preserved, bred, and maintained over 300 generations of red-eyed wasps parasitizing rice moth eggs at the Experimental Entomology Laboratory, Institute of Ecology and Biological Resources, with a breeding process capable of producing sufficient numbers of wasps to be released into fields to eliminate vegetable pests.
In laboratory conditions, the breeding of six-spotted ladybugs and the two-spotted ladybug using black bean aphids (which are bred using inexpensive substrates) resulted in high egg-laying rates in generations 1 and 2 (55.77-79.53, 96 eggs/female) with a high hatching rate (71.45-87.88%). The breeding of the predatory rove beetle E. annulipes using cat food in plastic containers yielded a multiplication ratio of 5.6-8.1 times, with an average yield of 121.5-194.9 individuals from 15-35 initial breeding pairs, while using plastic basins resulted in a multiplication ratio of 7.8-9.3 times, with an average yield of 241.2-465.7 individuals from 30-50 initial breeding pairs. Breeding of three species of brown marmorated stink bugs, including red-necked stink bugs (S. falleni), black-necked stink bugs (S. croceovittatus), and brown stink bugs (C. fuscipennis) using diamondback moths (S. litura) and rice moth larvae (C. cephalonica) resulted in a breeding ratio of 17-19 individuals from one male-female pair.
On vegetables grown in greenhouses, releasing red-eyed wasps at a density of 740,000 individuals/ha showed a high parasitism rate of diamondback moth eggs by the wasps (73.43 – 83.33%) and reduced diamondback moth density compared to the control group without the wasp release. Releasing the two-spotted ladybug at a density of 1 individual/1m2 (releasing 2000 larvae and 6000 adults/8000m2) reduced the density of gray aphids on vegetables after six days compared to the control group without the ladybug release. Releasing predatory rove beetles on cabbage in closed greenhouses at a density of 1 individual/m2 can control gray aphid and cabbage looper densities. Releasing nymphs and adults of predatory brown marmorated stink bugs and two species of predatory red-necked stink bugs at a density of 0.2-0.5 individuals/m2 significantly reduced the density of lepidopteran pests compared to the control group without the release.
To achieve optimal results from the biological pest control model (without using chemical pesticides) for safe vegetable production following GAP in greenhouses, it is necessary to release predatory rove beetles (BĐK) and predatory stink bugs (BXBM) in February, release red-eyed wasps, BĐK, and BXBM in May, and release two batches of predatory ladybugs in December.
These studies demonstrate that developing the breeding of natural enemies of pests offers many benefits to the agricultural sector. In the future, this will be one of the effective measures to reduce production costs suitable for farmers’ financial capabilities, lower than the costs of purchasing pesticides, alleviate the pressure of pesticide pollution due to increasing pesticide use, and ensure consumer safety.
