Potato Leafhopper Control in Alfalfa// here is the normal content // ?>
J. Whalen & B. Cissel - Revised March 2016 IPM -2
Adult – 1/8 inch long, wedge shaped, pale green
Nymph – slightly smaller that the adult, wingless, lime green
Life History and Phenology
The potato leafhopper (PLH) is the most damaging insect pest found in Delaware alfalfa fields. This insect migrates to Delaware from the Gulf Coast states in late April to early May. Potato leafhoppers do not overwinter in our area so first cutting alfalfa generally escapes damage. The greatest losses occur on spring seedings and on the regrowth of second and third cuttings of established stands. Under favorable conditions, leafhoppers develop from the egg to adult stage in three weeks. Cool night temperatures or high temperatures above 95 degrees F will retard development.
Adults and nymphs feed on alfalfa; however, the most severe damage is caused by the nymphs. Feeding initially appears as a yellow wedge-shaped area on the leaf tips often referred to as "hopper burn.” In a short time, this yellowing will spread to the entire leaf. If economic infestations are not controlled, the entire field will appear yellow, stunted, and fail to grow again until the crop is harvested. Feeding damage can also result in destruction of new stands, excessive winter-kill the following year, and reduced protein content.
Sampling and Decision Making
On new spring seedings, begin sampling by mid-May, or as soon as plants are 3 inches tall. On established stands, begin sampling within a week after the first cutting and continue on a weekly basis until the final harvest. Take sweep net samples any time during the day as long as the foliage is dry. Take 10 sweeps in each of 10 locations to determine the number of leafhoppers per 100 sweeps. Examine 20 random stems to determine the plant height and plant growth stage.
The following thresholds can be used to make a leafhopper control decision:
|Average Stem Height (inches)||Number per 100 Sweeps|
|3 or less||20|
|4 to 6||50|
|7 to 10||100|
|11 or greater||150|
If alfalfa is more than 60 percent bud or flowering, consider harvesting in the next 7 days to avoid spraying. In this situation, the field should be re-sampled soon after harvest to determine the need for control. If the field cannot be harvested in 7 days and economic population levels are present, apply a short residual insecticide. If the alfalfa has experienced “hopper burn,” significant yield loss has already occurred and the field should be cut instead of sprayed.
Potato Leafhopper - Chemical Control Options
NOTE – The label is the law. Be sure to read the label before making any pesticide applications and observe all label restrictions including days from last application to harvest – varies for forage, hay and grazing
|Baythroid XL(beta-cyfluthrin)||0.8 - 1.6 fl oz|
|Dimethoate 400(dimethoate)||0.5 – 1.0 pt|
|Mustang MAXX 0.8 EC(zeta-cypermethrin)||2.24 – 4.0 fl oz|
|Perm-UP 3.2 EC(permethrin)||4.0 – 8.0 fl oz|
|Warrior II(lambda-cyhalothrin)||0.96 – 1.6 fl oz|
|Tombstone 2 EC(cyfluthrin)||0.8 – 1.6 fl oz|
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