In the Midwest and Eastern US, PLH are considered the most damaging insect pest to alfalfa yield and quality. PLH damage can lead to stunting, lower yields, reduced crude protein content, loss of forage palatability, and loss of stand density.
Here's some general information on PLH damage and management.
General Information
PLH control is generally needed during July and August in the Midwest and Eastern U.S.
Hot growing conditions can cause PLH populations to increase very quickly.
Pay special attention to new seedings and 3rd crop regrowth.
Threshold: 1 adult in 10 sweeps. Adults at threshold are an indication deadly immatures are not far behind. Immatures (nymphs) are the most damaging stage of PLH.
Do not spray stubble for PLH control; wait for 3-4 inches regrowth or about 5-6 days to entice PLH back into fields.
PLH can cause severe damage to alfalfa plants before the yellow “burn” appears on leaves; Use a sweep net to detect PLH before symptoms appear. Once symptoms appear, damage is already done.
Damage:
PLH causes a yellow V-shaped “hopper burn” pattern on leaves. Cell sap is extracted from plants, damaging the plant’s plumbing system (phloem and xylem), restricting water and nutrient flow.
“Hopper burn” is a result from the PLH injecting a toxin during nutrient extraction. Once the classic yellow Vshaped pattern appears, the damage is done. Purple coloration often occurs as plant sugars produced in leaves are unable to be processed normally.
Stunted plants will have reduced root growth, water usage and weeds can often gain advantage.
Reduces yield potential; yield losses up to 0.5 DM Ton/acre per cutting or more.
Reduces quality and crude protein, increases nondigestible NDF fiber levels resulting in reduced forage intakes and palatability.
Weakens alfalfa plant health allowing for other foliar diseases and stress to alfalfa.
New seedings are especially susceptible to PLH damage and can result in yield
CROPLAN Forage Specialist Jeff Jackson provides more information on potato leafhoppers in alfalfa in this video:
Contact your local Premier agronomist for more information on PLH management.
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If spring weather got in the way of planting your alfalfa, you're not out of luck yet. Summer seeding is still a solid option and it comes with some real advantages when done right.
August may not be a traditional planting month, but it’s a crucial time for growers looking to establish alfalfa or prepare for fall crops. For most of our trade territory, alfalfa should be seeded by August 30, ideally 6–8 weeks before the first killing frost to ensure strong root and top growth before winter. After September 1, success rates drop significantly.
