Description of the Pest
Adults are small, black to gray flies with yellow markings. Females puncture leaves to feed on plant sap and lay eggs within the leaf tissues. After 2 to 4 days, eggs hatch and larvae feed between the upper and lower surface of the leaves, making distinctive winding, whitish tunnels or mines that are often the first clue that leafminers are present. Larvae emerge from the mines and pupate on the leaf surface, or more commonly, in cracks in the soil. Many generations occur each year, and the entire life cycle can be completed in less than 3 weeks when the weather is warm.
Damage
The primary damage caused by the chrysanthemum leafminer is the mining of the leaf by the larvae. When infestations are severe, the plant's photosynthetic capacity is reduced, and there is a reduction in crop yield.
Management
Chrysanthemum leafminer is usually kept in control by naturally occurring parasites and does not require any additional control efforts. All precautions should be taken to ensure that the parasites are not killed by pesticide sprays applied for other pests. In cases of severe infestation, a treatment may be warranted.
Biological Control
Biological control normally keeps leafminers in check, but outbreaks may occur following the disruption of their parasites with broad-spectrum insecticides. These leafminers are attacked and effectively controlled by an eulophid wasp (Chrysacharis ainsleii) as well as other species in the Diglyphus, Haltocoptera, and Opius genera.
Organically Acceptable Methods
Biological controls and sprays of the Entrust formulation of spinosad are acceptable for use on organically certified crops.
| Common name | Amount to use | 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. | SPINOSAD | |||
| (Entrust)# | 1.5–3 oz | 4 | 2 | |
| MODE-OF-ACTION GROUP NUMBER1: 5 | ||||
| COMMENTS: For resistance management, do not make more than two consecutive applications of group 5 insecticides. Check with organic certifier to determine which products are organically acceptable. | ||||
| B. | SPINETORAM | |||
| (Radiant SC) | 6–8 fl oz | 4 | 2 | |
| MODE-OF-ACTION GROUP NUMBER1: 5 | ||||
| COMMENTS: Label suggests adding an adjuvant to improve control. For resistance management, do not make more than two consecutive applications of group 5 insecticides. | ||||
| C. | BIFENTHRIN | |||
| (Brigade WSB) | 16 oz | 12 | 5 | |
| (Brigade 2 EC) | 6.4 fl oz | 12 | 5 | |
| MODE-OF-ACTION GROUP NUMBER1: 3A | ||||
| COMMENTS: Do not exceed 16 oz/acre between bud formation and harvest. Do not exceed 0.5 lb a.i./acre per season. | ||||
| ‡ | 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. |
| 1 | Rotate insecticides with a different mode-of-action group number, and do not use the 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. Mode-of-action group numbers are assigned by IRAC (Insecticide Resistance Action Committee). |
| # | Acceptable for use on organically grown produce. |