[Smart Farmers] Are cockroaches an invasive alien species? What is the difference between the new Latin cockroach species "Xiao Qiang"?

In recent years, my country's economy has developed rapidly, and the demand for various raw materials has continued to increase. The more types of imported raw materials, the wider the sources, and the increasing number of them year by year, the more diverse and complex the transportation methods in China, making it more hidden for pests and diseases, and increasing the difficulty of inspection and quarantine. These "stowaways" that may successfully evade quarantine are called alien species. Their invasion not only harms my country's agricultural production and ecological environment, but also threatens people's health and biodiversity.

In November, Zhongshan Port Customs under Gongbei Customs intercepted two species of Blattaria, commonly known as cockroaches, which were not found in China, from inbound logs. In my country, they are nicknamed "Xiao Qiang" because of their tenacious vitality and difficulty in prevention and control. The "Xiao Qiang" family is huge. There are currently about 4,337 known cockroach species in the world, and there are about 250 species in my country. The number of known cockroach species has increased in recent years, but the increase is slow. Cockroaches are one of the important vectors of disease for customs quarantine. It is worth noting that among the cockroaches intercepted this time, in addition to the reported Dorne Blattaria, there is also a new species of Blattaria that is reported for the first time in the world. What are the characteristics of the two newly intercepted "foreign cockroaches", what is the difference between them and "domestic cockroaches", and what potential hazards do they have?

The cockroaches intercepted from the logs this time belong to the genus Blatta, family Blattari, subfamily Blattari, and are mainly distributed in Latin America. The more common cockroaches in my country are German cockroaches. The two have certain differences in external morphology, which can be distinguished by body size, color, wings, pronotum and other characteristics:

1. Body size: The new species of Latin cockroach seized by the customs this time is 5.8mm long, while the other cockroach intercepted is Latin cockroach Dohn, which is 4.3mm long. Even with its wings, the total length is only 4.8mm. The common German cockroach in my country is about 13-19mm long. The two intercepted "foreign cockroaches" are only about half the size of "domestic cockroaches".

2. Color and wing characteristics: The two intercepted Latin cockroaches are yellowish brown in color. The right wing of the Dohnian Latin cockroach is divided into opaque and transparent areas, and the hind wings are incomplete. The right wing of the new species of Latin cockroach also has transparent and opaque areas, but the transparent area is more obvious. The forewings are shorter than the end of the abdomen, and the hindwings are underdeveloped. The wings of the German cockroach completely cover the tail and are brown to dark brown.

3. Characteristics of the pronotum: The middle of the posterior edge of the pronotum of the new species of Latin cockroach and the Latin cockroach of Don is slightly concave, with a "Y"-shaped shallow groove, and the longitudinal groove extends to the posterior edge; the German cockroach has two dark brown to black brown longitudinal stripes on the pronotum.

Characteristic diagram of the pronotum of three cockroaches

Although the "foreign cockroaches" are very different from the "domestic cockroaches" in morphology, they also have many similarities. For example, the Latin cockroaches have the same mouthparts as the existing domestic cockroaches, which are mainly chewing mouthparts, mainly for chewing plants or solid tissues. If they are not intercepted and successfully invade this time, their tenacious vitality and rapid reproduction ability may cause harm to the seedlings of crops, thereby affecting agricultural production. At the same time, like most domestic cockroach species, the Latin cockroach is an important vector of disease, which may carry a variety of pathogenic microorganisms in its body, contaminating food, clothing and daily utensils, leaving unpleasant odors, and may also cause the spread of a variety of diseases, threatening the health of humans and animals.

The harm of cockroaches to food and agriculture (picture from the Internet)

Why do cockroaches have the nickname "Xiao Qiang"? Simply put, it is because they have strong vitality, reproduce quickly, migrate and hide well, and are difficult to control. For example, in the case of water but no food, female American cockroaches can survive for 90 days, and male cockroaches can survive for 43 days. Even in extremely harsh environments, they can still cannibalize each other to survive.

"Xiao Qiang" has a strong and fast reproductive capacity, lays a large number of eggs, and has a short offspring generation cycle. A mature female cockroach can produce an ootheca containing about 40 eggs per week, and can reproduce tens of thousands of offspring in a year. Some female cockroaches only need to mate once to achieve hermaphroditism, and can continue to lay eggs without mating.

Although some cockroaches have wings, only some species can fly or glide short distances. They mainly rely on their feet to move and crawl very fast. They are small, flexible and difficult to be found. They are easily spread by humans or illegally smuggled along with furniture, books or imported and exported goods, and invade other countries. They like to live in dark and humid hidden places, hiding during the day and coming out at night, making them difficult to be found and thus difficult to effectively prevent and control.

Cockroaches and their larvae and their living environment (picture from the Internet)

The latest intercepted Latin cockroach is a species not found in China. It has similarities with the familiar "cockroach" but also many differences. However, due to the lack of in-depth knowledge of it, it is imperative to effectively prevent the invasion of "foreign cockroaches". So how can we keep it out?

1. Prevention at the source: Strengthen customs quarantine in import trade, strictly prevent imported goods from carrying invasive species, do a good job in disinfecting insect eggs, try to disinfect imported goods before they enter the country, and prevent "foreign cockroaches" from entering my country at the source.

2. Focus on popular science: Enhance the public’s awareness of invasive alien species, especially for key groups such as those engaged in foreign trade, import and export trade, so that people can pay attention to the importance of pollution-free imported goods at the source.

3. Prevention before it arrives: Through scientific and systematic research on the intercepted Latin cockroaches, its occurrence and spread can be prevented in advance; secondly, chemical control should be carried out regularly in key places, and sticky boards should be placed in places where they may move to kill them or they should be trapped manually and then disinfected with alcohol and incinerated in a closed manner at high temperature; biological control is the most effective prevention and control method for "Xiaoqiang", such as releasing natural enemies of cockroaches to prey on them.

Author: Ruan Dongxiao (Undergraduate intern at the South Subtropical Crops Research Institute of the Chinese Academy of Tropical Agricultural Sciences, sophomore student at Yunnan Agricultural University)

Scientific review: Wu Jingbo (Assistant Researcher at the South Asian Tropical Crops Research Institute, Chinese Academy of Tropical Agricultural Sciences, and off-campus tutor at Yunnan Agricultural University)

References:

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