Detailed Methods for Controlling Pests of Tropical Orchids (Part Two)
5. Whiteflies
Whiteflies are pests of the family Aleyrodidae in the order Homoptera. The insects are relatively small, with white powdery waxy material covering the whole body, and they usually cluster on orchid plants. They are prone to occur when ventilation in the orchid greenhouse is poor. They often damage the new shoots, tender leaves and flower buds of orchids. When causing damage, they insert their piercing-sucking mouthparts from the underside of the leaves, sucking the sap from the plant tissues, causing the leaves to turn yellow and withered, and they often excrete large amounts of honeydew at the wound sites, causing sooty mold and the occurrence of brown rot, and even causing the death of the entire plant. Because whiteflies have strong reproductive capacity, they can reproduce 9~10 generations within a year in a greenhouse, and can form a huge number in a short time.
Control methods:
(1) Because the adult whiteflies have white waxy powdery material on their bodies, chemical control is better applied during the nymph stage. Commonly used are 2.5% deltamethrin, or 10% permethrin, or 20% fenvalerate diluted 2000 times, with good results;
(2) 40% dimethoate, or 40% omethoate, or 80% dichlorvos, or 50% malathion emulsion can also be used to kill them, once every 5~6 days, with 2~3 consecutive sprays.
(3) The dominant natural enemy Encarsia formosa, etc., can also be used, and also has a certain effect.
6. Leafminers
Leafminers are pests of the family Agromyzidae in the order Diptera. Their larvae are maggot-like, white, about 3 mm long, and adults mostly appear in early spring. When causing damage, adults lay eggs within the tissue at the leaf margins, which develop into larvae. The larvae mine and feed on the leaf mesophyll, forming white linear irregular mines, appearing tunnel-like. They not only destroy the leaf tissue, causing the orchids to lose their ornamental value, but the damaged parts are also prone to black rot, thereby causing the entire leaf and even the whole plant to rot and die. Leafminers can damage many species among tropical orchids, but are most serious on Paphiopedilum.
Control methods:
(1) For the control of leafminers, in the early stage of occurrence, a needle tip can be used to pierce through to the end and pick out the insect body to kill it. When the infestation is more serious, the infested leaves should be removed promptly and destroyed.
(2) When using pesticide control, when the larvae first mine the leaves and cause damage, spray 40% dimethoate emulsion or 40% omethoate emulsion 1000 times, or 50% fenthion emulsion 1500 times, or 50% dichlorvos emulsion 1000 times. Once a week, 3 consecutive times is sufficient.
7. Caterpillars
These are the larvae of butterflies or moths in the order Lepidoptera. They gnaw on the new shoots, new roots, new leaves and young inflorescences, flower buds, petals and other tender tissues of tropical orchids. Generally, the parts damaged by them are difficult to restore to their original state, and the harmfulness is great. There are two ways caterpillars damage Dendrobium orchids. One is that in the early morning, caterpillars quickly crawl from around the orchid site to the orchid seedlings and in a short time devour large amounts of tender orchid tissue; the other is that during the daytime, butterflies or moths first lay eggs around the tender tissues of the orchids, and after the insect bodies hatch, they devour the new shoots. For example, the moth known as the bagworm, whose larvae can weave themselves a "bag" on the orchid plant, gnawing on the leaves, flower buds or petals of the orchid plant.
Control methods:
(1) For caterpillar control, prevention is primary. Weeds on the pot surface or around the orchid site should be cleared, and a small amount of quicklime should be sprinkled on the ground passages where caterpillars crawl;
(2) Drive away butterflies or moths that fly into the orchid greenhouse, prevent egg-laying and carry out manual capture and killing;
(3) Regularly spray 40% omethoate emulsion 1000 times, or 50% dichlorvos emulsion 1000 times for control.
8. Cockroaches
The cockroaches that harm tropical orchids are divided into household cockroaches and field cockroaches. They damage the root tips and tender shoots of tropical orchids. During the day they generally hide in orchid pots or among miscellaneous objects, and come out to move at night.
Control methods: Cockroaches have strong reproductive capacity and relatively high resistance to pesticides, so prevention is generally primary. First, prevent them from hiding in orchid pots. A layer of fine-mesh plastic screen can be placed at the bottom of the pot to prevent cockroaches from entering. When they have already occurred, the whole pot can be immersed in 1000 times omethoate for 5 minutes to kill the cockroaches. In addition, boric acid mixed with white sugar can be made into a paste for trapping and killing, and insecticides such as cockroach killer can also be used for spraying and killing.
9. Ants
The harm of ants to tropical orchids is mainly shown in that they often build nests in orchid pots, causing damage to the growth of orchid rhizomes and leaves.
Control methods: 80% dichlorvos 800 times solution can be used to drench the ant nest at the bottom of the pot, or it can be sprayed on the orchid plants for control.
10. Snails and slugs
Snails and slugs belong to mollusks. Snails have a hard protective shell, while slugs have no shell. They all occur one generation each year. These two types of animals mostly hide in dark, moist places during the day and come out to move at night, especially in the early morning or evening after heavy rain, coming out in groups to gnaw on orchid young roots, tender leaves and flowers. Because of their relatively large food intake, they can often eat up an entire small orchid seedling in one night. When snails and slugs crawl past, they leave shiny transparent slime trail lines on the orchid leaves, affecting the ornamental value of the orchids. Snails and slugs often hide in gaps between stones and voids in pots during low temperatures in winter.
Control methods:
(1) Usually pay attention to the cleaning and hygiene inside the greenhouse, and remove dead branches and fallen leaves promptly. Once discovered, carry out manual capture and killing. If manual capture and killing is not possible, poison bait must be used for trapping and killing. Metaldehyde can be used, bran mixed with arsenic, trichlorfon, etc., sprinkled in the places where they frequently move;
(2) Trichlorfon, deltamethrin, etc. can also be sprayed around the orchid plants, on the benches and flower pots, or tea seed cake water can be splashed around the orchid root zone, or 8% metaldehyde granules, quicklime, 6% acetaldehyde granules, saturated salt water, etc. can be sprinkled on the surface of the medium;
(3) 50% phoxim, 80% dichlorvos, 40% omethoate, etc. at 1000~1500 times solution can also be used, sprayed once every 5~7 days, 3~5 consecutive times.
(4) When growing at home, place several dishes of beer around the orchid plants before evening, and the next morning slugs can be seen dead drunk in the dishes.
11. Earthworms
Earthworms are beneficial in ground-planted flowers for loosening the soil and improving soil fertility, but in the pot cultivation of tropical orchids, because they devour the young roots of orchid plants, or damage the young roots of orchid plants during burrowing and moving back and forth, they can cause stagnation of orchid plant growth.
Control methods: Chlordane or heptachlor, carbaryl powder can be used at 1.0~1.5 grams per sq m for control, or 1:15 tea seed cake water can be used for splashing, which can achieve good results.
12. Rats
The harm of rats to tropical orchids is mainly shown in gnawing on orchid seedlings, medium seedlings and even large seedlings, as well as flower buds, flower spikes, flower bracts, and even the pseudobulbs of flowering plants, affecting the growth of orchid plants, causing reduced production or affecting ornamental value.
Control methods: Rat traps, electric catchers or poison baits such as rodenticide can be used for capture and killing.