Video Transcript
Aphids are small insects that
pierce the stem of plants to feed on their sugars. When doing this, they can transmit
many viruses to the plant. What is the best way to prevent the
spread of viruses by aphids? (A) Removing all infected plants,
(B) growing all plants in hot climates, (C) spraying plants with insecticides, or
(D) treating plants with antimicrobials.
Aphids use their piercing mouth
parts to suck sap out of the xylem and phloem cells in plant stems and leaves. The feeding activity of aphids can
directly damage plants and transmit plant pathogens, including viruses. The question asks us to determine
the best way to prevent the spread of viruses by aphids. The word “best” tells us that more
than one answer choice is likely to help slow down or prevent the spread of viruses
but that we need to find the most effective and efficient method. The simplest way to prevent the
spread of viruses by aphids would be to prevent them from feeding on plants in the
first place. So let’s go through the answer
choices to see if any of them could easily prevent aphid feeding.
Answer choice (A) suggests removing
all the plants that are infected with viruses, shown in yellow in the diagram. This would slow down the rate of
virus transmission because without infected plants to feed on, aphids could no
longer pick up and spread the virus. However, this method does not
control for aphids on noninfected plants that may be carrying a virus but have not
yet transmitted that virus to the plant. It also doesn’t take into account
the fact that it may take days or weeks for a plant to show visible signs of
infection after the transmission of a virus or that aphids can produce winged
individuals that can migrate between plants, taking the virus with them. So we can rule out choice (A)
because it’s definitely not the best way to prevent the spread of viruses.
Growing the plants in a hot climate
could help control the aphid population and slow virus transmission, because many
species of aphids prefer moderate temperatures. However, there are some aphid
species that thrive at high temperatures, as well as certain viruses that can spread
more easily in hot climates. Since it’s not clear if growing
plants in hot climates would prevent virus transmission or make it worse, let’s rule
this answer choice out.
An insecticide is a substance that
kills insects, either by directly poisoning them or by interfering with their life
cycle to prevent reproduction. In either case, spraying the plants
with insecticides would prevent aphid infestation and feeding, which would in turn
prevent virus transmission. There are a large variety of
insecticides available to home gardeners and farmers, and application by spraying is
relatively easy. So spraying plants with
insecticides is a good contender for the best answer. But let’s check our last choice
before we decide.
Antimicrobials are substances that
kill microscopic organisms or biological agents, such as viruses. Plants actually produce their own
antimicrobial substances to deal with pathogens. Treating plants with antivirals,
which are a class of antimicrobials that target specific viruses, could help prevent
their spread. However, researching and developing
an antiviral that treats a specific type of virus is a lengthy and expensive
process. In addition, the question tells us
that aphids transmit many viruses. So several different types of
antivirals would probably be necessary. Finally, the application of an
antimicrobial can be quite complicated because it must reach pathogens inside of
plant cells versus just being applied to the surface of the plant like many
insecticides.
So we can conclude that the best
way to prevent the spread of viruses by aphids is to spray the plants with
insecticides.
