Diagnosis – Insect or Disease?

 

Identify the problem:

·        If leaves are chewed or mottled/speckled or if you see a white cottony substance on it  the problem is probably an insect rather than a fungus. 

 

There are 2 types of insects – Chewing insects and sucking insects.

 

Chewing insects – Caterpillars and beetles.

·       Caterpillars chew around the edges of leaves.  Caterpillars that attack cannas chew on leaves before they unfurl, thus leaves emerge with a “line” of holes.

·       Beetles (Japanese beetles, potato beetles) often chew the leaf in a way which makes tiny holes over the entire surface of the leaf, leaving the leaf “filigreed” or looking like lace.

 

Controlling chewing insects –

·        We don’t know of a completely safe product that will control chewing insects.  We offer two chemicals that must be applied carefully to avoid harm to the customer or the environment.

·       Liquid Sevin controls beetles and caterpillars.  It kills them on contact, thus you must be able to see the pest that is doing the damage.

·       Ortho Systemic Insect Killer controls BOTH chewing and sucking insects.  It kills on contact AND is absorbed by the plant and the pest dies when it eats the plant.  Use Ortho Systemic when you cannot see the pest that is doing the damage.

·       Ultra-Lite Oil does NOT control chewing insects.  They are too big to be suffocated by oil.

 

Sucking Insects – Aphids, thrips, spider mites, scale, mealy-bug, lace-bug.

·       These insects cause the leaves to look mottled or speckled.

 

Controlling sucking insects –

·       Two options – A completely safe product, but one which will require several applications to control the pest OR several chemicals which will control the pest with fewer applications, but which must be applied carefully to avoid harm to the customer and the environment.

·       Ultra-Lite Oil is completely safe, a non-chemical, which simply suffocates sucking insects when sprayed over top of the pest.  Since these insects live on the undersides of the leaves, it is important to spray the undersides, not the tops of the leaves.  Mix 2 tablespoons of Ultra-Lite Oil with a gallon of water and apply with a sprayer which produces a fine spray-mist (not a hose-end sprayer). Apply once a week. 

·       Ortho Systemic Insect Killer controls sucking AND chewing insects.  It is absorbed by the plant and the insects die when they attack the plant.  Mix 2-3 tablespoons of Ortho Systemic with a gallon of water and apply with a sprayer which produces a fine spray-mist (not a hose-end sprayer).  Avoid getting Ortho Systemic on your skin or breathing it.

·        Concern controls sucking and chewing insects.  It kills the pest on contact, so you must be sure to get the spray on the pest.  Concern is sold in a small

“ready-to-use” bottle, so is useful only for smaller plants, not larger plants or

trees.  Avoid getting Concern on your skin or breathing it.

 

Identify the insect for your customer

·        Mealy Bugs - If white cottony stuff “hops” when you touch it, it is mealy-bug. 

Use Ortho Systemic, Concern or Ultra-Light Oil.

·        Scale - If white cottony stuff doesn’t move when you touch it and it is gooey

       inside, it is scale.  Use Ortho Systemic or Ultra Light Oil. 

·        Thrips - If flower buds open with brown streaks or don’t open all the way, and

you see lots of tiny brown specks moving around inside the flower, these

are thrips.  Use Ortho Systemic.

·       Spider Mites or Lace Bugs - If you don’t see any insects, but the leaf is mottled or speckled, it is probably spider mites or lace-bugs. 

·        Bag worms - Look like 1-2” “cones” which belong on the plant.  If the plant is

small, pick off as many as you can, then spray with Ortho Systemic.  If it is a large plant, you don’t need to pick off any, just spray with Ortho Systemic.

·       Tent caterpillars - Live in a nearly-transparent “tent”.  They come out periodically to chew leaves, then return to the tent.  Cut off the branch the tent is attached to and dispose of it and the tent.  If you can’t reach the tent, spray Ortho Systemic on the tent or leaves.  

 

Identify the problem – There are 2 types of fungus 

Leaf fungus

·       If a leaf has a white powder or black soot substance on it, the white substance is probably powdery mildew and the black substance is probably sooty mold.

·       Leaf fungus is most often seen in hot, humid weather.

·       Don’t confuse spray residue on leaves with powdery mildew.  Some plants (hollies and dwarf nandinas) come in from our growers with white spray residue when the grower sprayed the plants preventatively. 

 

Controlling leaf fungus -

Two options – Just as with pesticides, you have two options to control powdery mildew and sooty mold – A completely safe, non-chemical, which will require several applications to control the fungus OR several chemicals which will control fungus with fewer applications, but which must be applied carefully to avoid harm to the customer and the environment.

·       Ultra-Lite Oil controls fungus when 2 tablespoons of ordinary baking soda and 2 tablespoons of Ultra-Lite Oil are mixed with 1 gallon of water and sprayed on the plant with a sprayer that produces a fine mist (not a hose-end sprayer).   This mixture simply changes the pH of the leaf surface so fungus cannot grow.

·       Ferti-lome Liquid Fungicide controls powdery mildew and sooty mold on crapemyrtles and black spot fungus on roses.  It contains the chemical, daconil.  Use TBSP per gallon of water in a sprayer that produces a fine mist (not a hose-end sprayer).  Avoid getting this chemical on your skin or breathing it.   

·        Fung-onil controls fungus when sprayed on affected leaves.  It contains the chemical, daconil, and often kills the fungus in one application.  Fung-onil is sold in a small “ready-to-use” bottle, so it is useful only for smaller plants.  For larger plants and trees, use one of the other two products.  Avoid getting this chemical on your skin or breathing it.

 

Root fungus

When you notice leaves which are crispy or wilted, brown, black or yellow or have spots on them which don’t look like insect damage and they don’t have a white or black powdery substance on them, the plant is probably suffering from too little water, too much water or a root fungus.

·       (1) Too little water, (2) too much water and (3) root fungus ALL result in the same symptons.  This is because all three of these problems prevent the roots from pumping water up to the leaves.  Leaves may turn brown, black or yellow and may be crispy or wilted. 

·       Root fungus usually develops when the plant has been over-watered, either by rain or by the gardener. 

·       Unfortunately, there are no economical root fungicides available to the home-owner.  The only option is to correct the water problem, OR, if possible, raise the plant so it drains more quickly after rain and watering.