Welcome to Nongnghiepvietnam.org, Vietnam’s leading agricultural website! Today, we’ll explore the world of citrus trees – a popular crop with high economic value for farmers. However, alongside this economic potential, citrus trees are susceptible to various pests and diseases, impacting yield and fruit quality.
This article provides an overview of 16 common citrus pests and diseases and effective control solutions to help you protect your orchard.
Common Citrus Pests
1. Mealybugs
Characteristics:
- Armored scales: Hard shell, varied shape and color, easily detached from the body.
- Cottony cushion scales: Body length 2.5-4mm, covered in white, cotton-like wax.
Damage:
- Nymphs and adult females suck sap from leaves, branches, and fruit.
- Causes yellowing, leaf drop, branch dieback, tree death, fruit discoloration, and fruit drop.
- Honeydew attracts ants and sooty mold.
Control:
- Prune for open canopy and good air circulation.
- Remove weeds and fallen leaves.
- Regularly inspect the orchard.
- Spray insecticides: Checs usa 500WP, Lotoshine 400WP.
- Wash trees with soapy water before spraying.
- Apply Carbosulfan 5GR if mealybugs are at the base.
2. Thrips
Characteristics:
- Tiny size (0.1-0.2mm), yellow to orange-yellow color.
- Narrow wings with many small hairs.
Damage:
- Suck sap from new shoots, flowers, and young fruit.
- Causes leaf distortion, flower drop, reduced fruit set, and silvering or scabbing on fruit.
Control:
- Irrigate and spray when thrips first appear.
- Use yellow sticky traps.
- Spray insecticides: Fuze 24.7SC, Phenodan 20WP, Ace.Bio 30WP/Afeno, Ratoin 5WG, Chat 20WP.
3. Mites
Types of mites:
- Citrus rust mite (Phyllocoptruta oleivora)
- Citrus red mite (Panonychus citri)
- Broad mite (Polyphagotarsonemus latus)
Damage:
- Suck sap from leaves and fruit.
- Causes yellowing, leaf drop, russeting, and silvering of fruit, and fruit drop.
Control:
- Regularly inspect the orchard.
- Spray high-pressure water on mite-infested areas.
- Spray miticides: Diafen 50WP/Kyodo, Ratoin 5WG.
Citrus mites: Image depicting rust mites, red mites, and broad mites, and their damage to leaves and fruit, including yellowing, leaf drop, and russeting.
4. Asian Citrus Psyllid
Characteristics:
- Small size (2.5-3mm), brownish-grey color.
- Tilted abdomen when resting.
Damage:
- Sucks sap from young leaves, causing shoot dieback, leaf drop, and branch dieback.
- Honeydew attracts sooty mold.
- Transmits Citrus Greening Disease (Huanglongbing).
Control:
- Plant windbreaks.
- Avoid planting alternative host plants.
- Intercrop with guava.
- Protect natural enemies.
- Spray insecticides: Chat 20WP, Phenodan 20WP, Tvpymemos 650WG, Lotoshine 400WP.
5. Green Stink Bug
Characteristics:
- Shiny green color, body length 20-22mm.
- Two sharp spines on the front edge of the thorax.
Damage:
- Both adults and nymphs suck sap from fruit.
- Causes fruit yellowing, hardening, drop, and rot.
Control:
- Encourage weaver ants.
- Collect and destroy egg masses.
- Catch stink bugs with nets.
- Prune branches and maintain orchard hygiene.
- Spray insecticides: Shieldmate 2.5EC, Miktox 2.0EC, Smash 45EC.
6. Fruit Borers
Types of borers:
- Citrus flower moth (Prays citri)
- Citrus fruit borer (Citripestis sagittiferella)
Damage:
- Bore into the rind and flesh of the fruit, causing young fruit drop, fruit deformation, and fruit rot.
Control:
- Prune, fertilize, and mound soil.
- Collect and destroy infested fruit.
- Encourage weaver ants.
- Bag fruit.
- Spray insecticides: Shieldmate 2.5EC, Miktox 2.0EC, Smash 45EC.
7. Fruit-Piercing Moths
Characteristics:
- Large body, strong fliers, dark color.
- Long, strong proboscis.
Damage:
- Pierce and suck fruit juices, causing fruit rot and drying.
Control:
- Maintain orchard hygiene and remove vines.
- Catch moths with nets at night.
- Use bait traps.
- Bag fruit.
- Eliminate alternative host plants.
- Spray insecticides: Shieldmate 2.5EC, Miktox 2.0EC, Smash 45EC.
Fruit-piercing moth on citrus: Image of a fruit-piercing moth with its long proboscis attacking a citrus fruit, showcasing its characteristics and damage causing fruit rot and drying.
8. Citrus Leafminer
Characteristics:
- Very small moth (2mm), pale yellow color.
Damage:
- Larvae mine into leaves, creating serpentine tunnels.
- Causes leaf distortion, leaf drop, and creates entry points for bacteria.
Control:
- Prune and fertilize appropriately.
- Encourage weaver ants.
- Remove infested shoots and leaves.
- Spray insecticides: Chat 20WP, Phenodan 20WP, Lotoshine 400WP, Miktox 2.0EC, Smash 45EC.
Common Citrus Diseases
9. Citrus Black Spot
Causal agent: Fungus Phyllosticta citricarpa.
Symptoms:
- On leaves: Brown, sunken spots with dark brown margins and yellow halos.
- On fruit: Sunken, greyish-brown spots, appearing when fruit is mature or ripe.
Control:
- Collect and destroy infected fruit.
- Spray fungicides: Foli.Til 400EC/Gtop, Ky.Bul 72WP/Niko.
Citrus black spot: Image of black spot lesions on citrus leaves and fruit, showing the characteristic sunken, greyish-brown spots with dark margins and yellow halos.
10. Anthracnose
Causal agent: Fungus Colletotrichum sp.
Symptoms:
- On leaves: Circular, yellowish-brown spots with dark brown margins and concentric rings.
- On fruit: Small, round, light yellow, sunken spots with rough skin and fruit rot.
Control:
- Prune and maintain orchard hygiene.
- Limit overhead irrigation during disease presence.
- Spray fungicides: Foli.Til 400EC/Gtop, Amitagold 400SC/Asmiltatop Super.
11. Tristeza
Causal agent: Virus Citrus tristeza virus.
Symptoms:
- Vein clearing on leaves.
- Yellowing, branch dieback, and leaf drop.
- Small, cupped leaves with sunken midribs and swollen veins.
- Stem pitting.
- Yellowing at the bottom of the fruit and fruit drop.
Control:
- Use disease-free seedlings.
- Use resistant rootstocks.
- Plant trees at wider spacing.
- Remove infected trees.
- Control aphids.
Citrus tristeza: Image of a citrus tree affected by tristeza, showing symptoms like yellowing, branch dieback, leaf drop, stem pitting, and yellowing at the bottom of the fruit.
12. Phytophthora Foot Rot and Fruit Rot
Causal agent: Fungus Phytophthora sp.
Symptoms:
- On trunk: Dark lesions turning reddish-brown, bark cracking, and oozing of yellow gum.
- On fruit: Water-soaked lesions at the bottom of the fruit turning greyish-black and spreading.
Control:
- Use resistant rootstocks.
- Plant in well-drained soil.
- Collect and destroy infected plant debris.
- Prune, open canopy, and weed control.
- Paint trunks with fungicides: Biorosamin 72WP, Ky.Bul 72WP (Niko).
13. Fusarium Wilt and Root Rot
Causal agent: Fungus Fusarium solani.
Symptoms:
- Yellowing and leaf drop.
- Root rot starting from the tip, turning brown, and sloughing off of root bark.
Control:
- Plant in well-drained soil.
- Use disease-free seedlings.
- Apply lime.
- Prune and remove infected branches.
- Treat soil before planting.
- Apply organic fertilizers and microbial agents.
- Control nematodes and mealybugs.
- Drench with fungicides: PN – Coppercide 50WP, Super Humic 66%.
14. Citrus Scab
Causal agent: Fungus Elsinoe fawcettii.
Symptoms:
- On young branches and fruit: Small, light green spots turning light yellow and drying.
- On leaves: Curled and distorted leaves.
- On fruit: Rough, light yellow skin and distorted fruit.
Control:
- Plant disease-free seedlings at wider spacing and maintain orchard hygiene.
- Plant on raised beds to avoid waterlogging.
- Remove infected branches and leaves.
- Apply balanced fertilizers.
- Avoid overhead irrigation.
- Spray fungicides: PN – Coppercide 50WP, Foli.Til 400EC/Gtop.
15. Huanglongbing (Citrus Greening Disease)
Causal agent: Bacterium Liberobacter asiaticum.
Symptoms:
- Narrow, pointed leaves with blotchy mottled yellowing.
- Small, lopsided fruit with reversed maturity and aborted seeds.
- Root rot.
Control:
- Plant healthy, disease-free seedlings.
- Intercrop with guava.
- Plant trees at wider spacing.
- Prune and open canopy.
- Remove infected trees.
- Control Asian citrus psyllids.
Citrus greening disease (Huanglongbing): Image of citrus leaves exhibiting blotchy mottled yellowing, narrow, pointed shape, and image of small, lopsided fruit with reversed maturity.
16. Citrus Canker
Causal agent: Bacterium Xanthomonas campestris.
Symptoms:
- On leaves: Small, light yellow spots turning light brown with yellow halos.
- On fruit: Lesions similar to those on leaves, with rough skin, fruit cracking, and oozing of gum.
- On young branches: Raised, corky lesions and branch dieback.
Control:
- Use disease-free seedlings.
- Plant in well-drained soil.
- Plant trees at wider spacing, maintain orchard hygiene, and prune.
- Remove infected trees.
- Apply balanced fertilizers.
- Avoid overhead irrigation during disease presence.
- Spray bactericides: Bio.Bacteria 0.5SL/Elcarin, Olicide 9SL, Evanton 80SL, PN – Coppercide 50WP.
Conclusion
Identifying and controlling pests and diseases is crucial for achieving high yields and quality in citrus cultivation. We hope this article has provided valuable information to help you protect your orchard.
Share this article with friends and family who cultivate citrus trees! Visit Nongnghiepvietnam.org regularly for more helpful information. Wishing you a bountiful harvest!