Citrus: Good Growing Practices and Diagnosing Common Problems

Ryan Atwood Multi County Fruit Crops Extension Agent University of Florida/IFAS

Citrus production in Florida

Ryan’s home and office

Majority of sweet g p production orange

Majority of grapefruit production

Soil and Fertilizer Basics • Well drained soils • Preferred pH range 6.0-6.5 • Fertilizer considerations – Rate, analysis, timing and placement • Fertilization tied to – Rainfall – Irrigation I i i

Fertilization Young Trees • Analysis - 8 8-2-8 2 8 (others fine) N & K should be similar. • Placement - 6” from trunk to 1’ p past edge g of the canopy. g – Start after threat of freeze end • Timing by 1st October.

Fertilization Mature Trees • Amount needed will vary depending on crop size and variety of citrus. • Between 1-1.5 lbs N per tree per year. • Analysis –same as young tree, should add micro nutritional spray if needed d d ((tissue i samples). l ) • Placement – 1’ from trunk to 2’ pastt edge d off the th canopy.

Irrigation for Citrus • Irrigation is a major component of fertilizer program efficiency. • Citrus trees with sufficient water and nutrients grow stronger, tolerate pests and stresses better, yield more consistently, and produce high quality fruit. • Excessive or deficient irrigation or fertilization may result l iin reduced d d ffruit i quality. li

Irrigation for Citrus • Daily irrigation on newly planted trees, decreasing to every other day until established. • 1-3 times p per week for 2-3 hours on established trees (if receiving significant rainfall not necessary). • Extra irrigation critical to set and size fruit, so spring is an important time requiring extra H2O. • 1 inch per week during warm season • 1 inch per every two weeks during cool season

Citrus Problems Above or Below G Ground d • Most serious p problems for citrus trees occur below ground – hard to see – Symptoms similar, hard to determine for sure • Most problems you will encounter are not serious – will not kill the tree • Pesticide application will probably kill more good guys than bad guys

Below ground damage = Above ground symptoms

Above Ground • • • •

Diseases Fungal, Bacterial, Viral Diseases-Fungal, Mites Insects Nutritional disorders

Below Ground • Foot rot • Virus – Tristeza, Tristeza Exocortis Exocortis, Xyloporosis • Water • Nematodes N t d • Blight

Fungal Diseases • • • • • • • •

Greasy Spot Melanose Scab Alternaria Brown Spot Brown Rot Sooty Mold Post Bloom Fruit Drop Foot Rot

Greasy spot • Swelling on lower leaf surface. • Swollen tissue starts to collapse, turns brown and eventually black in color. • Infection causes premature leaf drop which occurs mostly l iin winter i and early spring.

Greasy spot remedy • 1 to 2 application of oil or oil & copper in M /J May/June and d JJuly. l

Melanose on fruit • Lesions are small, raised, superficial dots, pustules and irregularly g y shaped spots ranging g g from brick red to black. • They feel like sandpaper when touched. • Fruit becomes resistant to infection at about 12 weeks after petal fall. • Spores develop on twigs that have recently died.

Melanose on leaves and fruit

Scab • Small, somewhat circular, elevated spots on leaves and fruit. • Infection becomes wart-like structures, t t covered d with ith a corky pale tissue. • Pustules P t l may run together. t th

Scab

Alt Alternaria i b brown spott • The fungus attack fruit, leaves and young shoots of susceptible varieties. • First appears as small, slightly depressed black spots which can cause young fruit and leaves to fall. • Fruit usually immune to infection after reaching 3-4 months of age.

Alternaria

Melanose, Scab, and Alternaria R Remedy d • Prune out anyy dead wood in late winter/early spring. Especially after a freeze. • Spray copper every 3 weeks from ¼ expansion of spring flush till late June- early July. • Fungicides: Gem, Abound, or Headline.

Brown rot of fruit • Infected fruit exhibit a light brown, leathery decay. • Has H a characteristic h t i ti pungent, t rancid id odor. d • Fruit may become infected via soil contact, splash dispersal with soil particles or fruit fruit-toto fruit spread by windblown rain. • Infected fruit fall from tree tree. • Greater problem in late summer (Aug-Sept) if conditions are wet wet.

Brown Rot (Phytophthora ( h hh species) i ) on ffruit i

Brown rot remedy

• Prune up trees to allow good air flow thru the canopy. canopy • Can spray with copper or Phosphorus acid product (Prophyt/Phostrol/K (Prophyt/Phostrol/K-Phite/Nutriphite). Phite/Nutriphite) • P-acids will also help control foot rot and help promote root health health.

Sooty Mold • Dense, black fungus th t grows on the that th honeydew secreted by insects like aphids, scales, whiteflies and mealyy bugs. • Found on leaves, stem, and fruit. • Oil for control.

Postbloom fruit drop • The disease appears as peach to brown peachbrown-colored colored necrotic spots on petals of flowers. • Produces fruit drop and formation of persistent p buttons (calyces) that remain attached to stems. • No chemical control for homeowners.

Root/Foot Rot • Lesions on tree trunk usually on the bark at or just above the bud union on susceptible scions scions. • Lesions can eventually girdle the entire tree trunk trunk. • Planting at proper height in soil minimizes problem.

Root/Foot Rot Remedy • Prevent any wounding of the b k which bark hi h allows ll the disease into the tree. tree • P-acid • Ridomil or Ultraflourish

Foot Rot (Phytophthora ( h hh nicotianae))

Bacterial Diseases & Viroids • Citrus Canker • Citrus Greening or Huanglongbing (HLB) • Exocortis • Psorosis • Tristeza

Citrus Canker • Citrus canker is caused byy a bacterial pathogen Xanthomonas axonopodis pv. Citri. • The disease causes necrotic lesions on leaves, stems and fruit. • Severe infestation can cause defoliation, fruit drop, twig dieback, general tree decline and blemishes on fruit decline, fruit.

Citrus Canker

Citrus Canker • When there is moisture on the lesions, the bacteria ooze out and can spread to new growth or other trees. • Wind driven rain is the main dispersal agent, and d wind i d speeds d greater t th than 18 mph h aid id iin the penetration of bacteria thru stomatal pores or wounds wounds.

Citrus Canker • Movement of infected or exposed trees trees, seedlings, propagative material, and fruit is the primary p y means of spreading p g the canker p pathogen g over long distances. g tools, landscaping p g • Contaminated clothing, equipment, ladders, or containers are potential sources of infection. • Decontaminate all equipment associated with citrus tree work (70% alcohol solution)

Citrus Greening

G Greeningi Bl t h M Blotchy Mottle ttl

Greening – Sparse Foliation

Greening – Abnormal Fruit

Greening or Nutrient Deficiency?

Zinc deficiency

Greening symptoms

Greening – Disease Transmission • The Asian citrus psyllid is the vector of the disease • Spread by flight or wind dispersal p of Asian citrus psyllid • Greening is not spread by contact, tools or equipment

Greening – Transmission • Infected plant materials that may or may not show symptoms – citrus and ornamentals • Infected psyllids on ornamentals that mayy not be host to the bacterium

Chinese box orange, Box thorn

Greening - Management • You cannot prune away infection, if the plant has greening bacteria it is throughout • When removing a infected tree make sure to kill the stump with a herbicide to prevent sprouting. Resulting sprouts will contain the bacteria and be a source of inoculum

Greening – Management • Chemical options of psyllid management are limited for homeowners. homeowners • Horticultural oils will offer some control if psyllid adults and nymphs are present. • Eliminating greening and psyllid host plants from your yard and encouraging y g g beneficial insects is advised.

December 2007

December 2008 April

6-25 E

2009

6-26 E

Psorosis Exocortis

Tristesa

Pests- Mites Pests • • • • •

Spider Mites Pink citrus rust mite Citrus red mite Six spotted mite Rust mite

Spider Mites

Citrus red mite • Deep red to reddish purple in color color. • Citrus red mites feed on leaves, green twigs and fruit using piercingsucking mouthparts. • Mite feeding and environmental stress can lead to mesophyll collapse and leaf abscission. abscission

Six-spotted mite • Pale yellow, oval, 0.35 mm long, with one to three pairs of dark spots on the upper surface of the body body. • Found mostly along the petiole,, midrib,, or lateral p veins on the lower leaf surface usually in dense colonies covered with webbing. • Eggs are round and light yellow, with a short stalk or mask extending vertically.

Citrus rust mites Citrus rust mite and eggs.

Sun spott resulting S lti ffrom where citrus rust mite avoids feeding g on most sun exposed portion of the fruit.

Citrus Rust Mite, Phyllocoptruta oleivora (Ashmead)

Bronzing (summer or fall injury)

Sharkskin (spring injury)

Citrus Rust Mite Damage to Fruit

POPULA ATION DENSITY

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

Citrus rust mite curve showing population density by month for a typical year.

Pink citrus rust mite • Pink to reddish in color with a distinctive rounded bodyy or concave back. • Eggs are flattened, opaque p q and scattered along the leaf or fruit surfaces. • Often found at margins of young leaves.

Pink citrus rust mite d damage to ffruiti • PCRM begin feeding on very small fruit during A il and April dM May, especially during dry conditions conditions.

Pests- Insects Pests • • • • • • • • •

Scales Aphids Orange g Dog g White Fly Southern green stink bug Citrus leafminer Mealy Bug Katydid Grasshoppers

Snow scale Gl Glover scale l

Purple scale l

Caribbean black scale

Florida red scale on fruit.

Cottonycushion scale

Aphids • Produce live young asexually allowing for rapid population increases. • Infest newly expanding citrus terminals terminals, sucking sap from the growing leaves and stems. • Does not produce significant damage to mature t trees t but b t can damage young trees.

Citrus

leafminer

Orange Dog •

• Adult ->