When strawberries enter the flowering stage, the main pests on strawberries—aphids, thrips, spider mites, etc.—also begin to attack. Because spider mites, thrips, and aphids are small pests, they are highly concealed and difficult to detect in the early stage. However, they reproduce quickly and can easily cause disasters and cause large economic losses. Therefore, it is necessary to strengthen the pest situation survey to achieve early detection and early prevention and control.
1. Harmful symptoms
①Aphids
The main aphids that damage strawberries are cotton aphids and green peach aphids. Adults and nymphs gather on the underside of strawberry leaves, core leaves, and petioles, sucking strawberry juice and secreting honeydew. After the growth points and core leaves are damaged, the leaves curl and twist, affecting the normal growth of the plant.
②Thrips
After the strawberry leaves are damaged, the damaged leaves fade and leave tooth marks. The leaves initially show white spots and then join into pieces. When the damage is severe, the leaves become smaller, shrink, or even yellow, dry, and wither, affecting photosynthesis; during the flowering period, the leaves are damaged. Damage may cause stamen distortion, flower sterility, petal discoloration, etc. Adult insects can also damage fruits and affect the economic value of fruits. In addition, thrips can also spread a variety of viruses and cause damage to strawberry production.
③Starscream
The main species of spider mite that damages strawberries is the two-spotted leaf moth. The female end is dark red, with black spots on both sides of the body, oval. Overwintering eggs are red, non-overwintering young moths are red, and non-overwintering young moths are yellow. The moths in the overwintering generation are red, and the overwintering eggs in the non-overwintering generation are yellow and less pale yellow. There are dark spots on both sides of the body. Adult, young and adult moths suck sap on the underside of leaves and build webs. At the initial stage, sporadic chlorosis spots appear on the leaves, and in severe cases, white dots are scattered all over. In severe cases, the leaves scorch and fall off, causing premature plant aging.
2. Occurrence rules
①Aphids
Aphids mostly damage greenhouse strawberries by sucking sap from young leaves, petioles, and undersides of leaves, secreting honeydew to contaminate the leaves. At the same time, aphids spread viruses and degrade seedlings.
②Thrips
Warm, dry weather favors this. Nymphs and adults often lurk in the center of flowers and overlapping petals, and are highly concealed. It is difficult for ordinary insecticides to directly contact and kill the insects.
③Starscream
Young moths and early stage moths are not very active, while late stage stage stage moths are lively and gluttonous and have the habit of climbing upwards. It affects the lower leaves first and then spreads upward. High temperature and drought are most conducive to the occurrence of spider mites, and long-term high humidity conditions make it difficult to survive.
3. Prevention and control technology
①Aphids
(1) Agricultural measures: Remove old and diseased berry leaves in a timely manner and remove weeds around the greenhouse.
(2) Physical control: Set up insect-proof nets in ventilation locations, and set up yellow boards to trap and kill insects in the greenhouse.
Use from the planting period, use 10-20 pieces for each greenhouse, hang them at a height slightly higher than the strawberry plants by 10-20 cm, trap and kill winged aphids, and replace them regularly.
(3) Biological control: In the early stages of insect emergence, floating insects are released in the field, and 100 calories per acre (20 eggs per card) are released to capture and kill insects. Pay attention to protecting natural enemies such as grasshoppers, hoverflies, and aphid wasps.
(4) Chemical control: You can choose 25% thiamethoxam water-dispersible granules 3000-5000 times liquid, 3% acetamiprid emulsifiable concentrate 1500 times liquid, 1.8% abamectin EC 1000-1500 times liquid. Or spray 22% sulfluramid suspension 7000-8000 times on the leaves, and pay attention to rotation of medication. Pay attention to the safety interval of pesticides to avoid the development of pesticide resistance and phytotoxicity. (Note: For spray control, avoid the strawberry flowering period, and move bees out of the shed when applying pesticides.)
②Thrips
(1) Agricultural control: Clear weeds in vegetable fields and surrounding areas to reduce the population base of overwintering insects. It is more severe during drought, so the damage can be reduced by ensuring that plants are well irrigated.
(2) Physical control: Using blue or yellow insect traps to trap thrips has better effects. Hang 20-30 pieces per acre, and the lower edge of the color plate should be 15-20cm from the top of the plant, and increase as the crop grows.
(3) Biological control: Using natural enemies to hunt can effectively control the number of horses. If thrips are found in the greenhouse, promptly release 20,000 cucumber moths/acre once a month to effectively control the damage. Pesticides are not allowed to be used 7 days before and during the release period.
(4) Chemical control: When the insect load is low, use 2% abamectin EC 20-30 g/mu and 1.8% abamectin EC 60 ml/mu. In severe cases, 6% spinosad ethyl 20 ml/acre can be used for foliar spraying. When using pesticides, firstly, we must pay attention to the alternate use of different pesticides to weaken their resistance. Secondly, we must pay attention to spraying pesticides not only on the plants but also on the ground when spraying, because some mature larvae will turn into flies in the soil. (Amamectin and abamectin are toxic to bees. When spraying for control, avoid the strawberry flowering period, and move bees out of the shed when applying pesticides. Spinosad ethyl is not toxic to bees.)
③Starscream
(1) Agricultural prevention and control: Clear weeds in the field, eliminate the source of overwintering insects, knock off the lower old leaf insect leaves in time, and take them out of the field for centralized destruction.
(2) Biological control: Use natural enemies to control the population of red spider mites in the early stages of occurrence. Release Amblysei mites in the field, with 50-150 individuals/square meter, or Chilean phylloxera, with 3-6 individuals/square meter.
(3) Chemical prevention and control: Use at the initial stage of occurrence. You can choose 43% diphenhydrazate suspension concentrate 2000-3000 times liquid and 5% thiefenazine emulsifiable concentrate 1500 times liquid. Or use 1.8% avermectin 2000-3000 times for spraying and control once every 7 days. The effect is better if the agents are used alternately. (Diphenylhydrazine and abamectin are toxic to bees. When spraying for control, avoid the strawberry flowering period, and move bees out of the shed when using pesticides; fenacetate is not toxic to bees.)
