Keep Scouting for Potato Leafhoppers in Alfalfa

If you grow alfalfa, now is the time to scout those fields for potato leafhoppers.  Integrated pest management (IPM) scouts are finding potato leafhoppers (PLH) widely distributed across a number of alfalfa fields.  PLH numbers have ranged from low to well above economic treatment thresholds.   In addition, alfalfa growers have been calling about yellow leaves on alfalfa, one of the classic PLH damage symptoms.  Alfalfa growers should consider regular field scouting for PLH because this is one of the economically significant pests of alfalfa. 

            The potato leafhopper is a small bright green wedge shaped insect that arrives in our area each year on storm fronts from the Gulf Coast region.  PLH is a sucking insect.  PLH feeding causes stunting of alfalfa plants resulting in yield loss.  Excessive stress on plants by heavy PLH feeding can result in yield reductions in the current as well as subsequent cuttings.  A common symptom of PLH feeding is a wedge-shaped yellowing of leaf tips.  If you are noticing these symptoms, some damage has been done.  Regular scouting can help to detect PLH earlier and determine if there is a need for a rescue treatment.

            Scouting involves the use of a sweep net.  There is no other way to properly and accurately scout for PLH.  The procedure is to take three to five samples for each 25 acres from random areas within the field.  One sample consists of 10 pendulum sweeps.  After the 10-sweep sample, carefully inspect the net contents and count the number of PLH adults and nymphs.  For non-PLH resistant alfalfa varieties, treatment is warranted if the number of PLH adults and nymphs is equal to or greater than the average height of the alfalfa in inches. 

An OSU Extension fact sheet on PLH is available on-line at https://ohioline.osu.edu/factsheet/ENT-33.  A short video clip on how to scout for PLH and use a sweep net to sample for PLH is available at http://tiny.cc/PLHscouting featuring Mark Sulc, OSU Extension Forage Specialist.

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About the C.O.R.N. Newsletter

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.