Rice stem borer was first known in the world in 1863 and was first diagnosed in Iran in September 1351 by the Tonekabon Plant and Plant Disease Laboratory. Rice stem borer has certainly been imported to Iran from abroad and is currently the most important pest of rice cultivation in northern Iran and is prevalent in all rice-growing areas of Mazandaran and Gilan provinces.
The female butterfly is usually light yellow or brownish in color. The color of the male butterfly is almost gray. The front wings of the butterfly have a few silver spots and there are usually 5 brown dots in the middle of the wing. Both sexes are white. The body length of the butterflies is 10 to 13 mm. The fresh white eggs are yellowish-yellow, which gradually change to gray and then completely dark.
How to damage:
Insect larvae attack the stems of rice plants. If the young plant is attacked by larvae, the middle leaf turns yellow first and then dries little by little. If the attack of the pest coincides with the time of clustering and flowering, the seed in the unformed cluster will lead to dryness of the cluster. Contamination at the beginning of grain formation causes thinning and fragility of the grain. The first stage of damage is caused by the first generation of the pest. In this stage, with the growth of lateral stems, the plant reacts to the pest and the damage is prevented from increasing as much as possible. In the second stage, the damage to the plant is almost at the end of the vegetative stage and it is not possible to repair the damage through the growth of other lateral stems. Infected stems at this stage are broken at this stage, causing damage and destruction of adjacent healthy stems.
Passing the winter:
Rice stem borer spends the winter in northern Iran as a complete larva inside dry rice stalks or surrounding weeds. The first pupae formed from winter larvae are formed in the first decade of May. The pupae are without cocoons and form inside the remaining stem from the previous year. The minimum temperature required for pupation is 10 degrees Celsius. Pupae are damaged at temperatures above 35 degrees. The first pest moths appear in Gilan conditions from May 10, and reach their maximum exit in the second decade of June. The life of the butterflies is a maximum of one week. Winter generation butterflies usually lay their eggs on the upper or lower part of the upper leaves, while the next generation butterflies lay their eggs on the lower leaves or on the stem near the leaves.
Rising rice regions of Iran usually harvest rice fields from mid-to late summer. After harvesting, the rice fields are left as they are and sometimes the rice residues are allocated to the farm for livestock and they start cultivating rice again until the beginning of May of the following year.
In the long run, rice pests such as single-spotted butterfly larvae, stem borer, continue to grow and prepare themselves for a resurgence next year with more vigor and more numbers. Some of these larvae are transferred to the hives with cut pieces of rice and spend the winter in relatively warm places with better conditions. So we shelter the enemy with our own hands and give them about seven months to attack agriculture again. To prevent this, the following steps should be taken:
1- Harvesting the crop should be done as low as possible near the crown of the plant so that as few larvae as possible remain in the field.
2- The cut spikes are kept on the ground in the same field for a few days to dry, and then they are threshed with threshers that crush the straws completely and turn them into wheat straw so that any larvae inside the stem. Is crushed and destroyed.
3- Burn the straw left in the field with full care.
4- After burning the field, plow it with a tiller in two turns perpendicular to each other.
5. Flatten the plowed land as soon as possible.
6- Dig up and burn the weeds next to and around the fields that are the shelter of larvae in winter.
7- Inspect the rice cisterns every day to pick and destroy the infected leaves if the butterflies have laid eggs.
8- Avoid transferring seedlings that are infected or suspected of pests to the main land.
9- According to the experts of seed and seedling breeding, early cultivars should be used for planting as much as possible, and if possible, the treasuries should be protected with nylon so that the seedlings are ready for planting sooner. Overall, all rice cultivars in Mazandaran are more or less infected with stem borer, but in terms of damage, early and middle-aged cultivars suffer less damage because they are harvested before emergence or up to the beginning of the third generation larvae.
10- In the spring, when the butterflies leave, every farm should have a light trap. Optical traps are simple and are an ordinary lantern with a basin of water underneath. Butterflies that come to light fall into the water and perish.
B: Biological control :
Another effective method of controlling rice stem borer is the biological method. This method uses several species of predatory insects and two species of winter parasitic bees of the family Ichneumonidae, a species of larval parasitic bee called Apanteles and another species of egg parasitic bee of the family Trichogrammatidae, a species of beetle of the family Staphylinidea called Staphylinidea Dracula, which also feeds on the eggs of stem borer.
Andralus spinidems, which also prey on the pest, and a fungus called Beauveria brassiana, which infects larvae or pupae and also uses the pathogenic virus, are common enemies of the pest. Therefore, basic measures must be taken to maintain and control it.
Control of rice stem borer in the treasury using Trichogramma bee:
Biological control of bees:
If you use Trichogramma bees instead of chemical toxins, you can use 100 Trichocards (each card contains 1% gram of bee eggs being pupated) in 250 to 300 square meters of the treasury.
Control of rice stem borer in the main ground for the first time using Trichogramma bee:
In case of using Trichogramma bee, it is possible to use Trichocardus during 50% of pupal pupae in the weeds around the fields. 100 cards are enough for one hectare. The distance between each card should be 10 meters. In case of excessive pollution, the number of cards per hectare can be increased. Tricocards are produced in a place called Insectarium, which must be delivered to farmers after the cards are produced. Farmers should also install it on paddy land as soon as possible. Tricocard installation time should be in the morning or evening (not during the hot hours of the day.
Fight against rice stem borer in the main field for the second time using Trichogramma bee:
At this stage, the release of Trichogramma bee is done in the peak flight stage of the stem-eating butterfly. (Flight peak is when the maximum number of stem-eating butterflies collected by prey is determined. The prey of butterflies is obtained by lanterns and basins at the bottom or by other traps.) In case of interference between the second and third generation. In late or late planting cultivars, Trichogramma bees can be released twice.
In general, the following goals should be achieved in biological control:
1- Keeping the population of pests in the fields low 2- Increasing the population of beneficial insects using biological methods 3- Environmental health 4- Eliminating the areas of biological resistance in insects and pests caused by indiscriminate spraying 5- Creating a balance between beneficial insects and various pests 6- Reducing crop production costs per unit area by preventing uncontrolled spraying.
J: Chemical control :
1–Control and fight against stem borer in the treasury:
Stem-eating butterflies lay eggs under rice leaves in the treasury. Control of the treasury is easier and more cost-effective than the main land due to the low level of the treasury. The first generation of stem borer populations on farms can be greatly reduced if the treasuries are sprayed in public. 3 to 5 days before transplanting, the treasury can be sprayed with lindane toxin or one of the toxins. 150 g of 25% lindane toxin can be dissolved in 7 to 8 liters of water and sprayed with motor back spray (atomizer). When spraying the treasury, the water should be low and water should be prevented from entering and leaving the treasury for several days.
2. Fight against rice stem borer on the main land:
Based on the contamination of 2% of rice stems or the observation of 8 to 10 larvae of early age in one hundred plants, the field can be granulated with one of the chemical pesticides (5 or 10% granules or 4% padon granules). Diazinon 10% 15 kg and 5% 30 kg and Padan 4% 25 kg per hectare is sufficient. At the time of granulation, the field should have 4 to 5 cm of water and water flow from one plot to another should not be established. And water should not be allowed to enter or leave any plot for several days
3- Fighting against rice stem borer in the main land in the second turn:
Early sown cultivars are harvested or are being harvested before the outbreak of the second generation of the pest. Therefore, for the second generation of the pest, there is no need to control and fight. If 4% of rice odors are infected with stem borer or observe 10 early larvae in 100 stems, the field should be granulated.
Also based on Patak formula:
(Number of infected mounds divided by the total number of sampled mounds) Multiplication (Number of infected stems divided by the total number of sampled stems) If the field contamination in the first generation was more than 1% and the second generation was more than 2% He started spraying the field. Usually 16 hectares of heaps are randomly sampled. Water control in the granulation field must be strictly observed. In case of interference of the second generation and the third generation in late cultivars or late plantings, granulation can be sprayed.
4– Fight against rice stem borer in late planting and late cultivars:
Planting time of different cultivars in an area should be arranged and planned in such a way (late planting should be planted earlier than early planting) so that the cultivars do not differ much in terms of harvest. If in a region the cultivated cultivars are ripening or harvesting but there are one or two late ripening or late planting plots whose plants are green, bring all the butterflies of the region to that field and lay eggs there. As a result, the field becomes heavily infested with stem borer. If left unmanaged, they can be left astray and lose the right path. Therefore, the number of granules or sprays should be increased or the number of bee releases should be used more often.
In the second or third time, granulation in the amount of: 20 kg of 10% granules or 40 kg of 5% granules or 30 kg of 4% granular granules or 0.2% Ray Janet in the amount of 20 kg is required
Disadvantages of using chemical pesticides in the environment:
A- Pest resistance to toxins: Pests, like any other living thing, are resistant to substances that enter the body from the outside. Therefore, the use of a specific toxin in repeated periods causes resistance to pests. So that the poison no longer has its original function
B- Pest outbreak: Every year, if we look closely at the natural environment, we see that one pest is more than the others. And one of the many reasons for the pest is related to the use of toxins. Because it kills its natural enemy by spraying and fighting pests, and pests that are naturally resistant to the venom reproduce and form a population of the pest.
C- Destroying natural enemies: Creatures such as dragonflies, spiders, sparrows, swallows, whiteflies, starlings, frogs and ducks are good at hunting for their stem-eating, leaf-eating, single-spotted butterflies and larvae. Especially the presence of frogs and ducks. Of course, it should be noted that the excessive use of chemical pesticides is one of the most important factors reducing the population of these animals. The natural enemy of a creature in nature always lives next to it. Therefore, when we try to fight the pest in this way, its enemy also disappears and the problem of revolt arises.