How to properly control tree lice? Control method introduction

Tree lice, also known as Drosicha contrahens, pear round scale, pear round armoured scale, and wheel-heart scale, are widely distributed and mainly harm pears, apples, and other fruit trees, as well as peaches, plums, persimmons, and other fruit trees. Generally, female insects cluster densely on branches and trunks, while males often cluster on both sides of the main leaf veins. The damaged branches and trunks cause corkification of the cortex and the decline and death of phloem and vascular tissue. Let's take a look below at how to control tree lice!

Damage characteristics

Tree lice are the most common pests on flowers. Common species include Icerya purchasi, Chloropulvinaria floccifera, Pseudococcus comstocki, Eulecanium kunoense, Pseudaulacaspis pentagona, and Planococcus kraunhiae, 6 species in total, which often gather on branches, leaves, and fruits. Adults and nymphs insert their needle-like mouthparts into the leaf and branch tissues of flowers to suck sap, causing branches and leaves to wither, and even the whole plant to die, and can induce sooty mold, causing great harm.

Occurrence pattern

Tree lice occur 3 to 4 generations a year, with overlapping generations. They overwinter as nymphs and fertilized females on branches. In the following spring, the overwintering nymphs begin to cause damage. In late April and early May, they begin viviparous reproduction. From late June to July, the second-generation nymphs occur. From late August to early October, the third-generation nymphs occur. In mid-to-late November, the fourth-generation nymphs occur. Newly hatched nymphs rest under the mother's scale, and soon crawl out to spread and cause damage.

Control methods

1. Strengthen quarantine: Under natural conditions, tree lice have low activity, limited self-propagation and dispersal ability, and a certain degree of limited distribution. However, with the development of production, the exchange and transport of flowers are frequent, and the opportunities for human-assisted and long-distance spread of pests and diseases are increasing day by day. Quarantine work stipulates that flowers can only be transported if they do not carry dangerous pests and diseases. If pests and diseases are found, various effective measures should be taken to eliminate them and prevent further spread.

2. Manual control: During the process of cultivating flowers, if tree lice are found on individual branches or leaves, they can be gently brushed off with a soft brush, or the insect-infested branches and leaves can be cut off along with pruning. It is required to brush clean, cut clean, and burn them centrally; do not throw them away randomly.

3. Use natural enemies: For example, the Australian ladybird, the large red ladybird, which prey on Icerya purchasi, and the golden-yellow aphelinid wasp, the soft-scale aphelinid wasp, and the red-spotted ladybird, which parasitize armoured scales, are all effective natural enemies. They can be used to control the harm of tree lice and should be reasonably protected and utilized.

4. Chemical control: According to the various occurrence situations of tree lice, spray pesticides during the peak period of nymphs. At this time, most nymphs have recently hatched, the body surface has not yet secreted wax, and the scale has not yet formed, so pesticides are still easy to kill them. Spray once every 7 to 10 days, for 2 to 3 consecutive times. You can use 40% omethoate 1000-fold solution, or 50% malathion 1500-fold solution, or 255 phosmet 1000-fold solution, or 50% dichlorvos 1000-fold solution, or 2.5% deltamethrin 3000-fold solution for spray control, but it is best to choose the larval stage, when the wax layer has not formed and the control effect is good. If this good opportunity is missed, it is necessary to use specialized pesticides such as methidathion for control. You can also spray a 0.2% washing powder solution or 0.3% essential balm for control.