It's hot & dry: Watch
for potato leafhoppers
Many insect pests benefit from hot, dry conditions, and potato
leafhopper (PLH) is one of them. PLH do not overwinter in Ontario.
Each spring adults are carried by wind currents from southern Gulf
States and across the Great Lakes into Ontario. The first adults
arrive as early as mid May and continue to arrive well into June.
Nymphal development takes from 8-25 days, depending on temperature.
Three or four overlapping generations are produced each year and
remain active until killed by a hard frost. In hot, dry summer weather,
leafhopper populations can build to large numbers, requiring treatment.
Adults have a very wide host range, but plant maturity affects
suitability and not all support development of immature stages.
One of the first places they show up is in deciduous hosts, before
moving into annual crops, various weeds, vegetables, apples, strawberries
and grapes. Preferred hosts include alfalfa, beans, and potatoes.
The removal of a food source (such as alfalfa) usually causes adults
to migrate to other crops.
PLH adults are tiny (3 mm), wedge-shaped, and pale yellow-green
in colour. They are highly mobile and are easily disturbed when
you approach infested foliage. Nymphs are similar in appearance
but lack wings. When nymphs moult, they leave behind cast skins,
which can be seen during scouting activities. Older nymphs develop
"wing pads" that distinguish them from the fully winged
adults. Nymphs walk sideways or backwards, and rapidly move to the
underside of the leaf if disturbed.
Leafhoppers suck plant sap from foliage causing white stippling.
PLH are particularly damaging because they inject a toxin into the
plant while feeding, blocking vascular system flow and preventing
normal movement of water and nutrients to the affected area of the
plant. Foliage may become stunted and deformed. Leaves turn pale
green and curl downward at the margins. Leaf margins eventually
turn brittle and brown, a condition known as "hopperburn".
Water stress makes plants more susceptible to injury. Thresholds
have not been developed for most crops, but it takes only 2 or 3
PLH to cause a leaf to curl. Yield losses may occur before the development
of symptoms. Monitor for leafhoppers using sweep nets or visual
examination of leaves.
For more information visit
the CropIPM website.
