Attention! This year, conditions are ripe for an aphid outbreak—these aphids can even undergo morphological transformations, making them unimaginably formidable!

Release Date:

2020-03-27

　In 2020, influenced by a mild winter and an early‑season drought, average temperatures were higher than usual, leading to a more than three- to fourfold increase in overwintering aphid eggs compared with previous years. Coupled with recent temperature conditions that have created an ideal environment for aphid reproduction and migration, it is anticipated that aphid populations will experience explosive growth in 2020.
　　After overwintering, aphids migrate from their winter host to their summer host. Because overwintering eggs exhibit strong cold tolerance, temperature fluctuations can increase the initial population of migrating aphids. Improper management may lead to overlapping generations or severe leaf curling on new shoots; in severe cases, this impairs photosynthesis, weakening tree vigor. The honeydew they excrete is prone to colonization by saprophytic fungi, which can trigger disease outbreaks, ultimately causing extensive defoliation and even tree death.
　　In 2019, aphids on watermelon occurred at a severe level in the Huang-Huai-Hai region of China. Due to improper pesticide application, significant resistance mutations have emerged; in particular, resistance to insecticides among the yellow aphid of watermelon is increasing markedly. It is anticipated that by 2020, the yellow aphid of watermelon will exhibit a high degree of resistance.
　　 Cotton In 2019, aphids erupted across Xinjiang, causing substantial yield losses in many areas; and this year, 2020, in Xinjiang… Cotton Aphids will also continue to occur at relatively high densities.
　　I. Though tiny, aphids cause significant damage.
　　Aphids often congregate on leaves, tender stems, flower buds, and apical buds, where they pierce and suck sap, causing leaves to wrinkle, curl, and become deformed; in severe cases, this can lead to withering of branches and foliage, or even the death of the entire plant.
　　1. Aphids form colonies and directly pierce and feed on plant leaves and fruits, leading to nutrient depletion, stunted or delayed growth, premature senescence, poor crop vigor, inferior fruit quality, and reduced yields.
　　2. The honeydew secreted by aphids is a transparent, viscous, and sticky substance that inhibits plant physiological processes, impeding photosynthesis, and also serves as an excellent substrate for pathogenic fungi, thereby promoting the development of sooty mold and other diseases.
　　3. Aphids are also important vectors of viruses; they congregate on tender leaves, young shoots, flower buds, and other parts, causing deformed growth. This results in irregular wrinkling, curling, shedding, and distortion of the leaf undersides, as well as reduced or smaller flowers, and may even lead to wilting and death of the entire plant.
　　II. Black aphids, peach aphids, and yellow aphids are different—so which one is harder to control?
　　Aphids comprise numerous species, with common ones including wheat aphids, vegetable aphids, peach aphids, cotton aphids, and melon aphids. Based on visual identification, they can be categorized into black aphids, green aphids, peach aphids, yellow aphids, and summer‑season aphids. According to current statistics on resistance‑related mutations, peach aphids and yellow aphids exhibit the highest levels of pesticide resistance.
　　Like ordinary Wheat Aphids refer to the common wheat aphid, which typically has a black or greenish‑black appearance. This species exhibits a low coefficient of variation, and standard insecticides such as imidacloprid, thiamethoxam, and acetamiprid can effectively control it.
　　And like Cotton Cotton aphids on the plants may exhibit a mix of black, bluish, green, yellow, and even red coloration; this variability increases the coefficient of variation, making conventional insecticides much less effective.
　　The coefficient of variation for the apple yellow aphid has also been increasing year by year. Coupled with unscientific pesticide application, inadequate pest management, and its broad host range, control efforts remain equally challenging.
　　The peach aphid primarily infests fruit trees such as peach, plum, pear, apricot, and cherry, and can also colonize sweet peppers. Because its piercing‑sucking mouthparts produce copious honeydew, the damage it causes is particularly severe. On its primary hosts, the aphid often induces curling of young leaves, making it difficult for pesticides to penetrate. Coupled with an increased coefficient of variation, it has become one of the most challenging aphid species to control.
　　The watermelon yellow aphid has been the most damaging pest in watermelon-growing regions over the past two years; it also exhibits the highest coefficient of variation, the greatest resistance to pesticides, and the most explosive reproductive capacity among aphid species.
　　Aphids directly and indirectly damage a wide range of vegetables, including those in the Brassicaceae, Solanaceae, and Fabaceae families.
　　1. Reproductive Habits: Aphids reproduce via both parthenogenetic viviparity and sexual oviparity. In northern regions—whether in open fields or under protective cultivation—and in the subtropical zones of the south, parthenogenetic viviparity is the predominant mode of reproduction. In temperate and cold‑climate areas, as autumn weather turns cooler, winged aphids migrate to overwintering host plants such as peach trees (peach aphid), Sichuan pepper, and hibiscus (cotton aphid), where they give rise to sexual forms. After mating, these females lay overwintering eggs, which survive the winter. In the following spring, the eggs hatch into young aphids, known as “dry mothers.” The offspring produced by these dry mothers continue to reproduce on the overwintering hosts for several generations—typically about two months—before migrating to other hosts; they never return to their original overwintering hosts before the onset of autumn.
　　2. Overwintering habits: In the subtropical regions of southern China, this pest reproduces year-round without a distinct overwintering phase. In northern areas, it adopts two strategies: first, sexual aphids lay eggs and overwinter on their host plants—peach trees (for the peach‑green aphid) or Sichuan pepper and hibiscus trees (for the melon‑cotton aphid); second, in unheated greenhouses, when ambient temperatures fall below the range required for development, they overwinter inside the greenhouse; alternatively, they may overwinter outdoors in sheltered, sun‑exposed, warm microhabitats, such as behind windbreaks (for the peach‑green aphid).
　　III. Reasons for the Difficulty in Prevention and Control
　　1. Aphids have a rapid life cycle: after hatching, under favorable temperature conditions, they reach adulthood in about four days. Adult aphids reproduce parthenogenetically, and their reproductive period can last 2 to 3 months. Moreover, adult aphids produce large numbers of offspring; under suitable temperatures, a single female can give birth to more than ten nymphs per day.
　　2. The protected‑field greenhouse environment is highly favorable. Under dry, high‑temperature conditions, most aphids develop rapidly, with short reproductive cycles, numerous generations, and severe generational overlap. Such conditions within protected structures are particularly conducive to aphid development, allowing year‑round reproduction under suitable circumstances. Aphid populations can swell dramatically, producing dozens of generations annually and reproducing via parthenogenesis—traits that ensure rapid population expansion when temperature and humidity are optimal.
　　3. Winged dispersal and the “symbiosis” with ants: When space and resources are limited, parthenogenetic reproduction gives rise to large numbers of winged individuals, which migrate to plants of the same or closely related species to expand their damage. The honeydew secreted by aphids is a favorite food of ants, and the presence of ants can even help locate aphid colonies.
　　4. Increased Resistance: For a long time, aphid control has relied heavily on chemical pesticides; however, aphids have now developed high levels of resistance to many of these agents, resulting in diminished efficacy of chemical control measures.
　　III. Integrated pest management is the only way to eradicate aphids.
　　1. Early prevention and control: Accurately monitor the occurrence and development of aphids, and apply pesticides during the critical control period. During the aphid outbreak, conduct surveys every other day and implement preventive measures in advance. You can use systemic insecticides that target both above- and below-ground pests to effectively manage sucking‑mouthpart insects such as aphids, thrips, and whiteflies.
　　2. Exploit the aphids’ positive phototaxis by hanging yellow sticky traps to trap and kill them.
　　3. If aphids have already appeared or if there is overlapping of generations, it is recommended to use a combination of two or more active ingredients—such as flonicamid, thiamethoxam, flonicamid‑nitrile, and spirotetramat—along with acetamiprid and thiamethoxam for early prevention of an aphid outbreak. Additionally, an orange peel essential oil adjuvant may be added to enhance insecticidal efficacy. If a single application fails to reduce the initial pest population, a second follow-up treatment should be carried out promptly to further lower the aphid density.
　　4. Timing of application should be appropriate: During periods of high temperature, avoid midday and apply treatments in the early morning or late evening—preferably before 9 a.m. and after 6 p.m. This not only ensures safety but also prevents rapid evaporation of the spray solution caused by heat, which can reduce efficacy.