Description of the Pest
The western spotted and striped cucumber beetle occurs throughout California. The striped cucumber beetle occurs primarily in southern California.
Cucumber beetles overwinter as adults and become active in early spring. Adults lay eggs on the soil near the base of weeds and crops. As soon as they hatch, larvae begin to feed on plant roots. They complete their development in the soil. There are about three generations a year.
Cucumber beetles are about 0.36 inch (9 mm) long and either greenish yellow with black spots or alternating black and yellow stripes. They fly readily and migrate into orchards from alfalfa and other crops, and from uncultivated lands where cruciferous plants are abundant. Cucumber beetles thrive in moist areas and not well in heat; consequently orchards may be more attractive in hot weather during and after irrigation.
Cucumber beetles cause shallow feeding scars on the developing fruit.
Cucumber beetles are difficult to control. Damaging numbers of cucumber beetles are usually treated with insecticides.
Cucumber beetles are attacked by a variety of natural enemies, the most important being a parasitic tachinid fly, Celatoria diaborticae. Natural enemies are rarely effective in reducing cucumber beetle numbers below economically damaging levels.
There are no effective cultural controls for these pests.
Monitoring and Treatment Decisions
If cucumber beetles have caused damage in the past, traps can be used to monitor activity. Thresholds have not been established. Monitoring baits such as buffalo gourd root powder (Cidetrak D), which is a feeding stimulant, and eugenol, a pheromone, are usually combined with a stomach poison insecticide.
Insecticides must be directed at adult beetles. Applications of insecticides may be necessary if large numbers of beetles are present or feeding damage has been observed. Infestations that develop late in the season are usually not as damaging as those that begin earlier, because numbers tend to be lower. Nearby cornfields can be a source of late season infestations. Spotted and striped cucumber beetle larvae (called corn rootworm in corn) emerge from cornfields and fly into apricot orchards.
|Common name||Amount to use**||REI‡||PHI‡|
|(Example trade name)||(conc.)||(dilute)||(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.|
|(Asana XL)||4.8–14.5 fl oz||2–5.8 fl oz||12||14|
|MODE-OF-ACTION GROUP NUMBER1: 3A|
|COMMENTS: Use is not generally recommended on perennial crops in the San Joaquin Valley because high label rates can cause outbreaks of secondary pests. While low label rates reduce the potential for secondary outbreaks in the Sacramento Valley, they should only be used where resistance to organophosphates has not become a problem and other methods such as mating disruption are not feasible. Do not apply more than 14.5 fl oz product/acre per treatment.|
|(Sevin XLR PLUS)*||3–4 qt||0.75–1 qt||12||1|
|MODE-OF-ACTION GROUP NUMBER1: 1A|
|COMMENTS: Spray on trunks and crotches of trees at the beginning of spring activity. Once high numbers are found in trees such an application will no longer be effective, and a foliar spray, which may cause increased spider mite numbers, is necessary. Do not apply more than 14 qt/acre per crop.|
|(Trilogy, etc.)||1–2 %||4||0|
|MODE-OF-ACTION GROUP NUMBER1: Unknown. A botanical insecticide.|
|COMMENTS: Azadirachtin alone is not effective against adult cucumber beetles. Use Neem oil as a soil drench for eggs and larval stages. Efficacy has not been verified by UC research.|
|D.||BEAUVERIA BASSIANA STRAIN GHA|
|COMMENTS: Apply as a soil treatment in fall to infect overwintering beetles. Efficacy has not been verified by UC research.|
|E.||BUFFALO GOURD ROOT POWDER|
|(Cidetrak D)||Label rates||12||0|
|MODE-OF-ACTION GROUP NUMBER1: Gustatory stimulant.|
|COMMENTS: Has no insecticidal properties. Mix with stomach poison insecticide. Can be used as bait in monitoring devices or can be applied to plant surfaces.|
|**||For concentrate applications, use the amount given in 80 to 100 gal water/acre or lower if the label allows; for dilute application, amount is per 100 gal water to be applied in 300 to 400 gal water/acre, according to label.|
|‡||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.|
|#||Acceptable for use on organically grown produce.|
|*||Permit required from county agricultural commissioner for purchase or use.|
|1||Rotate chemicals 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 development of resistance. For example, the organophosphates have a group number of 1B; chemicals with a 1B group number should be alternated with chemicals that have a group number other than 1B. Mode-of-action group numbers are assigned by IRAC (Insecticide Resistance Action Committee).|