Description of the Pest
The two species Empoasca fabae and E. solana constitute over 90% of the Empoasca species found in sugarbeet. They are nearly identical morphologically and can only be distinguished by experts. The damage they cause is also nearly identical as are the treatment guidelines.
Empoasca leafhoppers are small (0.125 inch long), bright green, wedge-shaped insects. They may be distinguished from the green form of beet leafhopper by the lack of dark markings on the body. The small, wingless nymphs (immatures) are also wedge-shaped and green and move rapidly forward, backward, and from side to side. Both adults and immatures are found primarily on the underside of leaves.
Damage
Empoasca leafhoppers cause a symptom known as hopperburn in which the leaf margins turn yellow, particularly at the leaf tip, and these areas soon become necrotic. The entire leaf may become yellowed and the symptoms often resemble virus symptoms. The presence of adult and immature leafhoppers on the undersurface of the leaf serve to distinguish leafhopper injury from virus symptoms or mineral deficiencies. Empoasca leafhoppers do not spread beet curly top virus.
Management
Sample for Empoasca leafhoppers by counting the number of adults and nymphs per leaf. Examine a minimum of 10 leaves from 10 plants in at least four areas of the field. Pick fully expanded leaves, avoiding older leaves or leaves in contact with the ground. Also, select leaves that are shaded by other leaves because leafhoppers try to avoid the sun. Leafhoppers are found on the under surface of the leaf, so turn the leaf over and quickly count the number of leafhoppers; both adults and immatures can run very fast so you must be quick. Before starting your actual count, look at and count three to four leaves so that you will know what the leafhoppers look like, particularly the small ones, and how they behave. Then begin your sampling and actual counts.
Apply treatments when leafhoppers (both nymphs and adults) reach 10 to 15 per leaf. Use the lower number for fields 2 to 3 months up to several months from harvest. Use the higher number for fields within 1 to 2 months of harvest. Do not treat if fields are within 2 to 3 weeks of harvest.
| Common name | Amount per acre | REI‡ | PHI‡ | |
|---|---|---|---|---|
| (Example trade name) | (hours) | (days) | ||
| Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Always read the label of the product being used. | ||||
| A. | PHORATE* | |||
| (Thimet 20G) –at planting | 3.4–4.5 oz/1000 ft row | 72 | 30 | |
| (Thimet 20G) – postemergence | 4.9–7.5 lb | 72 | 30 | |
| MODE-OF-ACTION GROUP NUMBER1: 1B | ||||
| COMMENTS: Do not feed tops to livestock. Do not place Thimet granules in contact with seed. | ||||
| B. | NALED | |||
| (Dibrom 8)* | 1 pt | 48 | 2 | |
| MODE-OF-ACTION GROUP NUMBER1: 1B | ||||
| COMMENTS: Highly toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging. | ||||
| C. | ESFENVALERATE* | |||
| (Asana XL)* | 5.8–9.6 fl oz | 12 | 21 | |
| MODE-OF-ACTION GROUP NUMBER1: 3A | ||||
| COMMENTS: Highly toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging. | ||||
| ‡ | Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest. |
| * | Permit required from county agricultural commissioner for purchase or use. |
| 1 | Group numbers for insecticides and miticides are assigned by IRAC (Insecticide Resistance Action Committee). Rotate pesticides with a different mode-of-action group number, and do not use products with the same mode-of-action group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a group number of 1B; insecticides with a 1B group number should be alternated with insecticides that have a group number other than 1B. |