Every year, once lychee trees enter the stages of shoot flushing, flowering, and young fruit development, pests and diseases begin to strike in succession. Many orchards experience blackened leaves, hairy leaf undersides, bumpy leaf surfaces, and severe defoliation. Many growers confuse these symptoms, apply various pesticides, but see little improvement.

In reality, different pests and diseases have completely different mechanisms: some are fungal, some are algal, some are insect pests, and others are mite-induced. Misidentify the disease, and you've wasted your spray.

Below is a quick-reference comparison table for common lychee pests and diseases, organized from symptom identification → occurrence patterns → treatment timing → preferred pesticides. Save it for field use.

What's wrong with this disease? There are nearly circular spots on the leaf surface, ranging from grayish green to yellowish brown and rust red. They feel very rough, as if they are rusty. In the later stage, the leaves age and fall off prematurely.

Anthracnose – this one is insidious! In the early stage, leaf tips turn yellow – you won't notice it unless you're paying close attention. In the middle and late stages, it gets serious: black-brown necrotic lesions, fruit rot, defoliation, and fruit drop – patches of leaves falling off one after another. When the air is humid, pink sticky spore masses appear on the lesions – enough to make your skin crawl. The pathogen lurks quietly in diseased branches, infected fruits, and fallen leaves. When conditions are right – high temperatures, prolonged rainfall, and new shoot flushes – it strikes fast. This is a ticking time bomb! How to control it? Preventive application: difenoconazole 1,500× + pyraclostrobin 2,000× + organosilicone adjuvant 3,000×. For severe outbreaks: difenoconazole·azoxystrobin + prochloraz + kasugamycin – apply once every 7 days. Don't slack off!

Q: "Teacher, my new leaves are curling up with bumps – am I short on fertilizer?"

A: Short on fertilizer? No way! That's leaf gall midge!

Symptoms: Curled leaves, bumps, deformities, thickened tissue – when severe, new shoots just stall out. Peel open a bump – and you'll find the larvae every single time.

How it works: Adult midges lay eggs on tender leaves. Larvae hatch, burrow in, and suck sap. This triggers abnormal cell growth – forming galls. Think of it as the midge building a house inside your leaf!

clothianidin 1,500× + chlorantraniliprole 2,000× + emamectin benzoate 3,000×.

thiamethoxam + lambda-cyhalothrin + emamectin benzoate.

Grower's mistake: "Leaves are black – must be fungus. Load up the fungicides!"

The truth: Wrong target! The black sooty mold is just a symptom. The real problem is insects.

honeydew – a sticky, sugary substance.

The proof: Wipe off the black layer – the leaf tissue underneath is still green and healthy. That's how you know it's not a real disease!

spirotetramat 4,000× + imidacloprid 2,000× + mancozeb 600×.

Golden rule to remember: Sooty mold? Don't spray fungicide first – find the bugs!

The pathogen is not a fungus or a bacterium – it's the lychee erinose mite (gall mite)! Feeding on young leaves stimulates abnormal tissue proliferation – blisters on top, hairs on the bottom – both sides under attack!

abamectin 3,000× + bifenazate 2,000× + organosilicone adjuvant 3,000×.

abamectin + etoxazole + mineral oil – apply twice consecutively, 7 days apart.

Litchi leaf blight primarily affects the leaves of fruit trees. The disease initially occurs at the leaf tip or margin, appearing as brown spots, which later turn grayish-brown to grayish-white with dark brown or purplish-brown, slightly wavy margins. The boundary between diseased and healthy tissue is clearly defined. In the later stages, dense black small spots – the pycnidia (fruiting bodies) of the pathogen – appear on the lesions.

In short: brown tips → expanding gray-white lesions → purplish-tinged margins → dense black spots. Four steps to recognize it.

The pathogens causing leaf blight are complex and include various fungi such as Alternaria spp., Colletotrichum spp., and Pestalotiopsis spp. The pathogens overwinter on diseased or fallen leaves. In spring of the following year, they produce conidia (spores) that are spread by wind and rain.

Timeline: Nursery seedlings begin showing symptoms in early June; mature trees in July. The peak period is August–September, gradually declining after October. Be especially vigilant during years with prolonged autumn rainfall.

Core Principle: Build tree vigor first, spray second. Because this is a weak parasite, a healthy tree is much harder for it to infect.

Timely prune overcrowded branches and weak/diseased branches to improve air circulation and light penetration, reducing humidity in the orchard.

At the onset of disease, apply the following in rotation:

700× dilution, or

water-soluble powder 1,000× dilution

Rotate between these products to prevent resistance development

The disease affects leaves. Infected leaves develop small, nearly circular to irregular lesions, mostly starting from the leaf tip or margin, which later expand into grayish-brown lesions with black small spots – the acervuli (fruiting bodies) of the pathogen – appearing on the surface.

Apply the following fungicides at the early stage of disease:

Apply evenly by spraying, with a second application 10–15 days later.

The disease affects mature and old leaves. Lesions appear on the leaf surface or at the leaf margin. Initially, they are small brown spots, which gradually enlarge into circular to nearly circular lesions. Several lesions may coalesce to form larger areas of dead leaf tissue. The lesion centers are grayish-white with small black dots, while the margins are thin and brown.

At the early stage of disease, the following fungicides can be applied: