Leafhoppers at a
glance
Type of Damage
|
Pierce-sucking
|
Plant Symptoms
|
Browning & curling of leaf edges
|
Favourite Plant
|
Tomatoes & Potatoes
|
Control
|
Biological (predators: spiders & mantids)
|
Quick Intro
These jumping insects are common in the garden, especially
around the Acacia trees in our
garden. Not only do they attack plants, but they lower the plants’ condition
that allows secondary attack by other pests and diseases. They are easy to spot
on plants, but be careful as they can bite you too!
Science Stuff
Leafhoppers belong to the insect Order of Homoptera, which
means that their wings are completely membranous (unlike Hemiptera insects
where half of the wing is sclerotized or hardened. They are a major
plant-feeding group causing direct damage to plants as well as spreading plant
pathogens (disease). They produce ‘honeydew’, a sugary excretion which ants
collect as food.
Leafhoppers belong to the Cicadellidae family (cousins of
the cicadas J)
and contain many species, often brightly coloured. Their wings are held
roof-like over the body and their hind legs have a single row of spines. They
are excellent jumpers, which make them hard to catch, so leaf it to the ambush
predators J.
Habitat & Feeding
They are highly host specific, meaning that they feed
exclusively on one host and will adapt accordingly. A white patch occurs on
plant leaves after feeding, due to the destruction of chlorophyll (green
pigment) in that area. In high numbers the leaves start to brown and curl back
onto themselves. A characteristic v-shaped browning of the leaf tips is a
symptom known as ‘hopperburn’. In South Africa we have 350 known species and
20 000 species worldwide.
 |
| Hopperburn on tomato |
Diseases
Leafhoppers transmit viral diseases (maize streak virus),
fungal and bacterial diseases.
Potato Leafhopper (PLH)
I will be focusing on one specific leafhopper common in
vegetable gardens or agricultural lands. (It was quite the mission to identify
the leafhoppers in my garden, as my trusty insect book let me down and only had
7 species. So this meant going through zillions of pictures on Google to find
one with a scientific or common name.)
There are several species of potato leafhoppers, but the one
in my garden is Empoasca fabae. It
feeds on many cultivated crops including eggplants, strawberries, potatoes and
tomatoes. They prefer to attack my potatoes and tomatoes (likely due to both plants
belonging to the same family, Solanaceae). They are bright lime green with
white eyes – apparently there are six white dots on the back of the head that
can be seen with magnification, as if I can get close enough for that before
they jump! J Their nymphs look similar, but are smaller with no wings.
.JPG) |
| Potato LeafHopper Adult Empoasca fabae |
They arrive during spring time and can have several
generations per season. Depending on your local climate, the adults either
overwinter or migrate to warmer areas.
+nymph.jpg) |
| Potato leafhopper nymph Empoasca fabae |
I have another leafhopper species in my garden, but I can’t
identify it, I find many similar looking species, but not this exact one. I
have noticed that these are larger than the PLH and their bite is more painful!
J
 |
| Leafhopper Unidentified species |
Leafhoppers are tricky to control. Physical removal of
infected plants can be effective, but seeing as they will simply jump off or
migrate into the garden, physical control is likely only effective short term.
Chemical control: Is the most effective. But the problem
with chemical control (even home remedies) is that these insects are too ‘high’
up the evolutionary complexity scale and their pesticides will likely harm
other higher insects as well. There are some insecticidal soaps available.
Biological control: This will be the mantids and spiders,
wasps prefer caterpillars. I had a huge lack of mantids this season as none of
last seasons’ females laid eggs in my garden (should likely go do some hunting
for egg cases next season J). So I had a bit more of a problem with leafhoppers
this season, but the spiders and wasps managed to move into the gap left by the mantids
and kept most of them under control. (Also had more stink bugs in the garden as
well, mantids also ate those last year, check my Mantid post.)
Preventative tips
Healthy plants should be able to resist most of the damage
caused by leafhoppers and should produce well.
Apparently you should avoid over-fertilisation of your
plants as this will increase the leafhopper populations in your garden.
They lay their eggs on plant stems. Each female can lay 2-3
every day for up to 50 days. These eggs hatch in 7-10 days. So the removal of
spent or dead plants will likely decrease the amount of suitable egg laying
places. That includes regular weeding! J
If you are close to alfalfa fields you may have more
problems with PLH, especially when the alfalfa is harvested and the insects
need a new food source.
Something cool
A sister family, Membracidae, the Treehoppers have a
fascinating evolutionary phenomenon. They have a large pronotum, a part
of the prothorax, known as a helmet. The helmet usually resembles thorns and
aid camouflage. But, some species have developed very ornate helmets. Some
scientists speculate that these resemble aggressive ants or animal droppings.
 |
| Learhopper morphology Original picture: Eupteryx aurata, Sarefo, Wikipedia |
Prud’homme and colleagues (2011), investigated the strange
helmets of the treehoppers. They found that the helmets are actually appendages
that resemble a modified wing. There is a set of genes (known as a gene
family), the Hox gene family, present
in all animals and is responsible for the correct development of limbs/wings
during the formation of the embryo. The helmets of the treehoppers were
speculated to have ‘escaped’ the constraints of the Hox gene and where able to develop into diverse appendages. This
was due to the fact that, wings have a restricted shape due to their function
in flight, whereas the appendages can take on a number of different shapes to
facilitate camouflage. In the 250 million years of insect evolution, this is a
rare and unusual case – but if there is one thing that biology and especially
genetics has thought me , is that just about anything is possible, since nature
does not abide by the supposed rules that humans have J. So I just thought I
would share this interesting evolutionary bit with you – I hope I didn’t over-science it J.
Reference:Prud’homme B. et. al. (2011) Bodyplan innovation in treehoppers through the evolution of an extra wing-like appendage. Nature: 473 83-86.
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