BSPP ‘Plant Doctor’ Quiz #9 – December 2021

The correct answer is:

Yellowing:

It is sometimes called “Chlorosis”, but yellowing is generally a good description of the symptom when the plant has no other symptoms than looking paler than a healthy plant.

The incorrect answers were:

Pale: the plant could be considered as pale, but this is not a word often used to describe plant symptoms.

Necrotic: this term is used to describe tissue that has turned brown and is dead.

 Nitrogen deficient: this may be the cause of the symptom, but it is not the name of the symptom.

The correct answer is:

Wilt:

This is a common symptom caused by abiotic factors, insects and pathogens.  It always refers to a drooping of the leaves due to a lack of water in the leaves. Woody tissue cannot wilt as the structure is not maintained through water pressure, however the leaves on a woody branch may wilt.

The incorrect answers were:

Flaccid: it is true that the leaves are flaccid, but that is not the usual word to describe a plant in this state.

Collapsed: wilt is a far better word to describe the symptom.

Drooped: yes, the plant is drooped, but wilt is a much better description because it indicates why the plant is drooped (lack of water in the leaves).

The correct answer is:

Enations:

A seldom seen symptom, but it is characteristic of some diseases.

The incorrect answers were:

Galls: this term usually applies to undifferentiated growth on the surface of a plant.

Phyllody: this term may be coming up later in the quiz.

Fasciation: this term may be coming up later in the quiz.

The correct answer is:

Canker:

Canker is almost always a symptom of woody tissue, the pathogen attempts to invade the host and the host lays down material to prevent it. This on-going battle leads to a wound with raised edges.

The incorrect answers were:

Gall: this is an undifferentiated growth of host tissue and does not have this wound aspect to it.

Tumour: not a word that is frequently used in plant pathology.

Lesion:  the symptom could be described as a lesion, but as it is woody with enlarged edges, canker is a better term.

The correct answer is:

Phyllody:

Not a common symptom (except in sesame): phyllody is the production of leaves in place of petals.  Phytoplasmas, and occasionally viruses, can induce this symptom.

The incorrect answers were:

Witches’ broom: it could be considered to be a type of witches’ broom, but, as the leaves are replacing the petals and other floral parts, it is phyllody.

Proliferation: there is considerable proliferation at the top of the plant, but that is a general term for excessive growth.

Fasciation: there is no evidence of fasciation here.

The correct answer is:

Halo:

This phrase is used to describe the distressed host tissue at the edge of a leaf spot.  It is almost always yellow as seen here.

The incorrect answers were:

Corona: this is not a term used in plant pathology.

Border: the yellow halo is generally considered to be outside the border of the leaf spot.

Toxin zone: there may be toxins leaching out into the host tissue creating the halo, but that is not what it is called.

The correct answer is:

Cysts:

These are the cysts of the potato cyst nematode.  They are attached to roots just like nematode galls, but, unlike a gall, they are not made up of the plant tissue; this is the swollen body of the female nematode, packed full of eggs.

The incorrect answers were:

Galls: these are commonly associated with nematode infection (but not all nematodes cause galls). Cysts are much smaller than galls and are always of extremely similar size and appear clean, despite being in the soil.

Eggs: difficult to imagine what animal would have laid eggs in this haphazard way, most insects / animals will lay eggs bunched tightly together.

Sclerotia: they are always black and usually formed within the tissue and (it is difficult to tell) are much larger than nematode cysts.

Photo courtesy of Wikipedia

The correct answer is:

Gummosis:

When damaged by a pest, pathogen or even mechanical damage, some trees will start to produce resinous sap which will dribble down the trunk.  The technical word for this is ‘gummosis’.

The incorrect answers were:

Ooze: often called ooze, but this is not the correct term.

Bleeding: often called bleeding, but this is not the correct term.

Resination: this is a word I have just made up, no-one calls it resination.

The correct answer is:

Rugose:

The leaves are clearly distorted but not thickened into true blisters and the leaf is its normal thickness.  It is a very common kind of leaf distortion often called blistering but this is actually incorrect.

The incorrect answers were:

Blistered: the leaves have not swollen into blisters.

Crinkled : not a word that is used in plant pathology.

Shrinkled: a word that is sometimes used in some countries but is not an official word.

The correct answer is:

Mosaic:

This term is often used to describe virally infected plants, but all viral infections do not lead to mosaic symptoms and not all mosaics are due to viral infection. Note that this leaf is also rugose.

The incorrect answers were:

Yellowed: some of the leaf is undoubtedly yellow, but it is the relationship between the yellow and green areas that are important.

Variegated: the leaf is variegated, and this is not wrong, but mosaic is the usual term used when describing viral symptoms.

Blotchy: it could be described as blotchy, but this term is not often used in plant pathology.