BSPP ‘Plant Doctor’ Quiz #19 – October 2022

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Aphids

It is unusual for aphids to attack underground but, as you can see, it does happen.

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Nematode attack

The galls seen on these roots are very typical of those produced by galling nematodes, Meloidogyne species.

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Take all

This disease caused by Gaeumannomyces graminis var. graminis produces indistinct symptoms above ground; stunting and yellowing.  The stubby black roots are characteristic.

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Pot bound:

This plant had outgrown its pot, the lateral roots appear healthy, but the main root growing down doubled back when it could not penetrate the base of the pot.

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Healthy

These plants, including the roots, were completely healthy (except for a tiny bit of powdery mildew which would not affect the roots).

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Nitrogen fixing nodules

These growths are pink and displaced to the side of the root, these two characteristics make a diagnosis simple.

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Physiological condition; no pathogen involved

This is “black heart” or “hollow heart” of potato. There are no external symptoms. It can develop in the field or in storage. This physiological condition is associated with low oxygen levels.

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Nematode cysts:

Cysts are much smaller than nodules or galls. The cyst is the dead body of the female nematode and remains firmly attached to the root.  These cysts are full of (200-400) nematode eggs and will survive for years in the soil, ready to infect another susceptible crop.

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Adventitious roots

The roots seen here were found growing inside the slightly swollen stem of a tomato plant.  The swelling appeared to be associated with Fusarium infection (comments welcome).

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Virus: Beet necrotic yellow vein virus

This is a disease called Rhizomania, extremely unusual symptoms for a virus; it is transmitted by the soil-borne fungus Polymyxa betae. Foliar symptoms show various degrees of stunting, wilting, and yellowing and often may be confused with a nutritional deficiency.