Hello everyone, I am Zhi Nongjun. The last issue introduced the grassland night moth to everyone, and the first major pest in 2020 is a foregone conclusion! Eat more raw fast, farmer friends early prevention
Many friends commented below, and some friends asked, how did grass greed cross the Atlantic? Zhi Nongjun first answered everyone: Grass greed by laying eggs on containers or transporting them with some fresh fruits and vegetables, after arriving at the shore, they are not quarantined. This has caused the spread of the grassland nightcrawler in Africa.
Since the beginning of spring this year, plant protection stations in various places have successively reported to monitor the harm of grassland night moth, and the harm has spread to more than 2.4 million mu. Yunnan, Guangxi, Hunan and Guizhou were seriously affected. Anhui has reported the discovery of grassland night moth harm, and at the same time, the corn in the Huang-Huai-Hai area will immediately enter the trumpet period, and the grass greed will continue to push north to harm the Huang-Huai-Hai corn has become a fixed trend.
However, recently, armyworms have also jumped out to harm corn in Shaanxi, and armyworms in the northeast in 17 years have also caused significant losses to corn production. At the same time, the local close relatives of the grassland moth, the beet moth, the twill moth and the armyworm, also harm the corn, which are all moths.
Different moths, control methods are not the same, once the identification is wrong, the wrong control agents and methods are adopted, either causing excessive use of pesticides to pollute the environment, or insufficient prevention and control, causing pest harm and affecting food production. So how do we differentiate them? First of all, we must recognize what the grass moth looks like.
<h1 class= "pgc-h-arrow-right" > First, what does the grass moth look like? </h1>
The grass moth has 4 insect states (see figure below), each of which is different, and only the two insect states of adults and larvae can be easily distinguished from other moths.
Figure 1 Adult worms (adults, able to get married and have children)
Next, Zhi Nongjun will combine the pictures to give you a detailed explanation, how to identify the grass greed! As can be seen from the picture, the female and male moths of the grassland night moth look different:
The male moth is more abundantly striated, and looking at the place where the red circle in the figure is circled, there is an oval ring spot, the lower corner of the ring has a white wedge pattern, and there is a clear near-triangular white spot on the outer edge of the wing.
Female moths are much more low-key, and those who do not wear mink jackets wear gray clothes, which also makes it more difficult for grass moths to distinguish them from other moths.
Female moth male moth after mating to get the crystallization of love - grass greed eggs, because in China's grassland night moth is mainly corn type, like to eat corn, so grass greed will generally lay eggs on the leaves of corn, so that the larvae inside the eggs can be directly on the leaves after hatching to eat harm.
Fig. 2 Egg block (crystallization of female moth male moth love)
The larvae are the only insect states that harm the crop by the grassland night moth, and it is a critical period for prevention and control!
The body length of the grass-incubated larvae is only about 1.7 mm, and when it reaches the mature larvae, it can grow to about 35 mm, which is about 20 times larger. These nutrients of the long body are absorbed by the harmful crops, so this stage is a critical period for the prevention and control of the grassland moth, especially in the stage of hatching larvae, the body is not so tough, taking advantage of his weakness to kill him.
Once you wait until the old mature larval period, you can eat and pull, metabolism is fast, drug resistance is much stronger than the larvae, the dosage of the drug is not enough, the drug is metabolized, resulting in the inexhaustible killing, and eventually the grain yield is reduced or even extinct.
Fig. 3 Larvae (morphology of harmful crops)
Fig. 4 Pupal (pupae become adults after pupae, completing the cycle)
<h1 class= "pgc-h-arrow-right" >2. How to distinguish between the grass moth and other moths? </h1>
There are ways in which adults look at the wings and the larvae look primarily at the head and back. The main pests that harm corn leaves in China are beet nocturnal moth, twill moth and armyworm, these 3 kinds of moths and grass greedy piece (Figure 5) are about the same size, mainly the markings and colors on the wings are somewhat different.
Fig. 5 Comparison of grassland moth with other moths (Guo Jingfei, Jing Dapeng et al. 2019)
As you can see from the figure:
The grass moth is grayish brown with a slight yellowish tinge, oval ring spots, nephroform spots are not obvious, the lower corner of the ring spots has a white wedge-shaped stripe, and the outer edge of the wing has a distinct near-triangular white spot.
Beet moths are grey-brown with distinctly pinkish-yellow rings and kidney-shaped spots.
The twill moth is gray-brown with complex markings, several white lines in the front half of the wing, and 3 distinct white diagonal lines in the middle of the wing, so it is called twill nocturnal moth.
Adult armyworms are yellowish brown to greyish brown with pale yellow ring spots and kidney-shaped spots, with 1 distinct small white spot below the spot and 1 small black spot on each side of the small white spot.
Fig. 6 Comparison of grassland night moth larvae with other larvae (Guo Jingfei, Jing Dapeng et al. 2019)
In terms of larvae, as can be seen from the image above:
The main features of the grass moth are white or pale yellow on the head, a "Y" pattern, and 4 black or black-brown spots on the tail, which are also called "four tubes".
Beet noctuid moth larvae are green , with a black or pale pink head and distinct yellowish-white or green longitudinal bands on either side of the body.
The twill moth also has a "Y" pattern on its head, and each segment of the body has a triangular black spot on each side.
The armyworm has a white line in the middle of the dorsal line, two black line clips on both sides, and 2 reddish-brown stripes on both sides.
<h1 class= "pgc-h-arrow-right" > three, is there any other way to tell if my corn is harmed by the meadow moth? </h1>
There is a way, the farmer jun this picture above tells you how to judge whether corn is harmed by grass greed.
Fig. 7 Field maize leaf hazards of the 1-2 instar larvae of the grassland nocturnal moth- no window is opened
1-2 year old larvae cause less harm and can also be recovered:
From Figure 7, you can see that there are many white dots or patches on the corn leaves, which is caused by the harm of the 1-2 year larvae of the grassland nightcrawler, as we said earlier, the individuals of the 1-2nd instar larvae are very small (about 1.7mm), so they eat limited, and each time they can only bite through the corn and have to eat the leaf flesh on the surface, so it causes a transparent film on the leaf, like a glass window, but it is not opened, and the experts also call this an unopened window.
If you find that your corn has such symptoms, you should take immediate control measures to control the pests as soon as possible, and if the control is done properly at this stage, the loss can be recovered.
3-6 year old larvae cause serious harm and are unable to return to the sky:
The other is the serious situation, from the following figure can be seen that the corn leaves have been bitten through a lot of holes, the middle of the "trumpet mouth" has been damaged, such corn has been difficult to ensure that there is no more yield, the loss has been irreparable.
Fig. 8 Field maize leaf hazard of grassland nocturnal moth 3-6 instar larvae - hole opening window
This serious situation is caused by the harm of the 3-6 year old larvae of the grassland night moth, the larvae above 3 years old gradually increase in size, the amount of food increases dramatically, and the mouth bite ability is getting stronger and stronger, and it is easy to bite the corn leaves, especially like the delicious "trumpet mouth" young leaves.
Therefore, the prevention and control of grass greed must be early, once it enters the 3rd age, the amount of medication and the type of medication must increase, and the harm is particularly large. The control of grass greed must be carried out before the larvae are 2 years old. This stage is the golden age for the control of the grassland moth, and once it is missed, it may be regrettable.
<h1 class= "pgc-h-arrow-right" > actually has a very detailed 9-level classification table for the hazard level of the grassland moth, which Isongjun shares with you for reference here. </h1>
Have you mastered the identification method of the grassland moth? Grass greed needs early detection and early prevention! If you have any questions, welcome to leave a message~
bibliography
Guo Jingfei, Jing Dapeng, Tai Hongkun, Zhang Aihong, He Kanglai and Wang Zhenying (2019). "Morphological characteristics of the grassland moth and comparison with three maize field pest characteristics and morphologically similar Lepidoptera insects." 45(02): 7-12.