UF UNIVERSITY of
2006 Florida Plant Disease Management Guide:
Macadamia (Macadamia integrifolia) 1
Ronald D. French-Monar and Pamela D. Roberts2
ALGAL SPOT (Cephaleuros
Symptoms: Leaves become greenish-gray, with
circular spots that are slightly raised and prominent.
These spots will appear red when the alga is
reproducing. When leaves are heavily infected, some
leaf drop may occur. The alga on branches can cause
bark scaling and cracking of limbs.
Chemical Controls: No EPA-approved
fungicides are legal for this use.
Symptoms: Nuts, twigs, branches and leaves are
susceptible to this pathogen. Brown lesions develop
on leaves and nuts from rain-splashed spores coming
from twig infections. Husks of nuts develop soft
brown lesions ranging in size from 1/8 in. to less than
1/2 in. in diameter. Some nut drop may occur. Disease
is enhanced under high humidity.
Cultural Controls: Collect and destroy fallen
infected leaves and other plant material.
Chemical Controls: Fungicides applied at first
disease onset will aid in disease management. See
Symptoms: Moist periods with cool temperatures
between 60-840F favor the disease. Small, brown
spots develop on petals and quickly spread to the
flower stalk racemee). The entire flower stalk may
blacken and die within 2 days. Dead flower petals
stay in place. The fungus produces spores as a
grayish-brown mass from infected tissue.
Chemical Controls: Apply preventive
fungicides during moist, cool weather which favors
infection. See Table 1 for fungicides.
1. This document is PDMG-V3-20, one of a series of the Department of Plant Pathology, 2006 Florida Plant Disease Management Guide, Florida
Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Revised: August 2006. Please visit the EDIS Web site at
2. Ronald D. French-Monar, Ph.D., Research Associate, Plant Pathology Department, Southwest Florida Research and Education Center--Immokalee, FL;
Pamela D. Roberts, Ph.D., Associate Professor, Plant Pathology Department, Southwest Florida Research and Education Center--Immokalee, FL; Florida
Cooperative Exention Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL.
The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and
other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex,
sexual orientation, marital status, national origin, political opinions or affiliations. U.S. Department of Agriculture, Cooperative Extension Service,
University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Larry
2006 Florida Plant Disease Management Guide: Macadamia (Macadamia inteqrifolia) 2
ROOT ROT (Phytophthora
cinnamomi, Pythium sp.)
Symptoms: Root rots, caused by these
oomycetes, primarily cause a rot of the small feeder
roots, which become darkened and die. Heavy
infestation may result in the absence of such roots
which normally would allow for moisture uptake.
Therefore, poor soil drainage will result in water
accumulation in the soil in the absence of a good root
Cultural Controls: Good drainage of soils will
allow for adequate soil moisture.
Chemical Controls: See Table 1.
SOOTY MOLD (Capnodium spp.,
Signs/Symptoms: Sooty mold is the common
name for several species of fungi that grow on the
honeydew secretions on leaves and other plant parts.
Scales, aphids, psyllids, and other insects that secrete
honeydew can be responsible for sooty mold. Fungal
mycelium is melanized (darkened), giving the
appearance of soot covering the plant part. These
fungi are ectoparasitic (growing on the surface) and
will not infect plants. However, sunlight penetration
is reduced and can result in stunted growth or yield
Cultural Controls: Cultural practices that will
manage insect populations responsible for honeydew
secretions in plant parts should be implemented. Such
practices may include careful pruning of affected
plant parts, control of ants that protect the insects
responsible for honeydew, and high pressure washing
of tissue with water and, if possible, with soap.
Chemical Controls: Use insecticides for control
of ants and secretors of honeydew.
2006 Florida Plant Disease Management Guide: Macadamia (Macadamia inteqrifolia) 3
Table 1. Chemical controls for diseases of Macadamia.
Chemical Fungicide Maximum Rate / Min. Days Pertinent Remarks b
Group Acre I to Harvest Diseases or
Applic. Season Pathogens
Abound (azoxystrobin) 11 12.3 fl 2.31 45 Anthracnose May add an adjuvant at
oz/A quarts/A Other leaf spots recommended rate.
Do not make 2
Gem (trifloxystrobin) 11 2.9 fl 15.4 fl oz 60 sequential applications
oz/A of this product or other
Qol fungicides. Do not
Heritage (azoxystrobin) 11 6.4 oz/A 24 Ib 45 make more than 4
season for fungicides
in this group.
Badge, Champ DP, Champ M1 Anthracnose See label for rates
2F, Champion WP, Botytris Raceme
Copper-Count-N, Cuprofix blight
Disperss, Kocide 101, Kocide
2000, Kocide DF, Nordox
75WG, Nu-Cop 50WP,
Nu-Cop 3L, Nu-Cop 50DF,
(Various copper formulations)
Fosphite (Potassium Phytophthora See label for various
phosphate) application guidelines
Pristine (Boscalid + 7+ 11 14.5 58 oz/A 14 Anthracnose Same as Abound
Pyraclostrobin) oz/A Other leaf spots
Subdue GR and Subdue Maxx 4 Phytophthora Non-bearing nursery
(mefenoxam) root rot trees. See label for
Topaz (Potassium phosphite) Phytophthora See label for various
___ __ application guidelines
aFungicide group (FRAC Code): Numbers (1-37) and letters (M, U, P) are used to distinguish the fungicide mode of action groups. All
fungicides within the same group (with same number or letter) indicate same active ingredient or similar mode of action. This
information must be considered for the fungicide resistance management decisions. M = Multi site inhibitors, fungicide resistance risk
is low; U = Recent molecules with unknown mode of action; P = host plant defense inducers. Source: http://www.frac.info/ (FRAC =
Fungicide Resistance Action Committee). Be sure to read a current product label before applying any chemicals.
blnformation provided in this table applies only to Florida. Be sure to read a current product label before applying any chemical. The
use of brand names and any mention or listing of commercial products or services in the publication does not imply endorsement by
the University of Florida Cooperative Extension Service nor discrimination against similar products or services not mentioned.