Cucurbits XXX-1

Striped Cucumber Beetle

Whitney S. Cranshaw & Michael J. Brewer

Striped Cucumber Beetle

 

Note: Cucurbits may be easily injured by formulations of some insecticides. It is often a good precaution to not apply insecticides when foliage is wet. Be sure to check label before using to make sure insecticide will not cause plant injury and/or perform a small-scale test application to verify safety.

Identification (and Life Cycle/Seasonal History)

There are several species of cucumber beetles, the most common that occurs on cucurbits is the striped cucumber beetle, Acalymma vittatum. The adults are prominent, flying around the foliage and flowers of older plants. Cucumber, squash, pumpkin, and melons, are highly preferred host plants. Adults are about six millimeters (1/3 inch) in length, yellow-green in color with three black narrow stripes that occur along the length of the back of the insect.

Adults overwinter in and around plant remnants and field borders. Adults are active at about the time of seedling emergence of its host plants. Foliage and stems of seedlings may be fed upon during this time. Eggs are laid at the base of plants in the spring/summer, and larvae develop principally on the underground stem and roots. Larvae are elongate, thin, and cream-colored. Adults emerge in the summer and feed on foliage, flowers, and the skin of developing fruit. There is usually only one generation per year; although two generations may occur in the southern part of Colorado.

Plant Response and Damage

Poor stand development (seedling feeding) is the most common serious damage. Plantings of cucurbits have been devastated by adult feeding within a few days after plant emergence. After establishment of the plant, about the time of presence of three fully expanded true leaves, the plant is much more tolerant of adult feeding. Later in the season, adults feeding may result in flower destruction and misshapen fruit. Bacterial blight, transmitted by this insect, is uncommon in drier areas of the country, such as our region. Tunneling by larvae of the underside of fruit laying of the soil surface may occur when high soil moisture causes the larvae to move upwards. Because bacterial blight is uncommon in our area, the striped cucumber beetle is primarily considered a seedling pest; although populations at times can become very dense resulting in substantial fruit/flower damage.

Larvae of the cucu8mber beetle may enter the fruit rind in areas in contact with soil. Such tunneling can introduce soft rots and scarring renders fruit unmarketable.  Problems occur most commonly when wet soil conditions persist during the period of fruit maturity, which induces migration of the larvae into fruit. 

Management Approaches

Biological Control
There are several parasites of cucumber beetles in our region. These include parasitic flies and wasps. They are unavailable commercially, but play a role in the natural regulation of cucumber beetles. Because these beetles are attracted to seedlings by host odor, adult beetles may occur in large numbers soon after plant emergence, despite the action of these parasites.

Cultural Control
In some situations, it may be effective to protect young seedlings with mechanical barriers of screening material. These materials are commercially available or home-made barriers can be made to protect plants in a garden. After establishment of the plant (after elongation of the first three true leaves), the plant is much more tolerant of adult feeding. For large-scale commercial plantings, expandable row coverings are available. Use of these materials may be particularly cost effective when the plants are being protected from other pests and the fruit is being placed in the organic market.

Chemical Control
Insecticides are most commonly applied during seedling emergence and during fruit development. In areas of high densities of cucumber beetles, multiple applications may be needed. Because cucumber beetles are attracted to host plant odor, large densities of beetles may arrive within a few days of plant emergence. For this reason, monitoring for beetles must be frequent (every other day) when plants are in the seedling stage. Less frequent monitoring is needed as the plant becomes more tolerant of adult feeding. Early season control of cucumber beetle adults, when warranted for seedling protection, may reduce later problems with the larvae. Control of larvae in fields after stand establishment will be poor.

 

There are no controls for larvae once they have begun to develop in the soil.  Larval problems can be prevented by controlling adults and preventing egg laying.  The critical period to control adults is two to five weeks prior to harvest.  Eggs laid earlier than this are unlikely to produce larvae in stages that will damage fruit. 

Note: not all products are registered for use in every crop. Check labeling for usage restrictions.

 

Product list for Striped Cucumber Beetle:

Insecticide

Product per acre

Preharvest Interval, Remarks

Sevin XLR+, 4F
Sevin 80S
Sevin 50W

1 qt
1.25 lb
2 lb

(0 days) A carbamate insecticide (carbaryl). Sevin 90S, 4F, and 50W formulations are highly hazardous to bees. Some rotations restrictions. May be used with sprinkler irrigation. 12 to 24 hour reentry proposed.

Thiodan 50W 
Thiodan 3E, Endocide 3E

1-2 lb
1.3-2.6 pt

(2 days) 48 hour reentry proposed. Some rotational restrictions with certain root  crops. Chlorinated hydrocarbon insecticide (endosulfan).

Guthion 35W1
Guthion 2S1, 2L1

1.4 lb
2 pt

(1 day) 48 to 72 hour reentry proposed. Labeled for chemigation. Guthion is an organophosphate insecticide (azinphosmethyl). Not for use in squash.

Asana XLR,1

5.8-9.6 fl oz

(3 days) Proposed 24 hour reentry interval. Pyrethroid insecticide (esfenvalerate).  Some rotation restrictions with root crops.  Melons and Zucchuni only.

Lannate 90SR

0.5-1 lb

(3 days) Carbamate insecticide (methomyl). Melons and Zucchini only.

Ambush 2E R,1
Ambush 25WPR,1

6.4-12.8 fl oz (2E)
6.4-12.8 fl oz (25WP)

1 day. Pyrethoroid insecticide.  Maximum 1.6 lb (AI)/acre per season.

Kryocide 96W

8-12

14 days.  Inorganic insecticide (sodium aluminoflouride) with stomach poison activity.

Adios

0.5-0.75 lb

0 days.  A unique carbaryl-based insecticide that contains attractions and feeding stimulants for cucumber and corn rootworm beetles.  Selective action limits be kill potential.  Maximum of 3.75 lbs may be applied in a season. 

Pounce 3.2ECR,1
Pounce 25WPR,1

4-8 fl oz (3.2E)
6.4-12.8 oz (25WP)

1 day. Pyrethroid insecticide. Maximum 1.6 lb (AI)/acre per season.

Capture 2ER,1

2.6 - 6.4 fl oz

3 days.  Pyrethroid insecticide.  Maximum 0.3 lb (AI)/acre/season. 

RRestricted use pesticide. 1Labeled for chemigation  2Generic active ingredient, several formulations.
The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.

 

 

Categories: Insects, Cucurbits, Cucumber, Melons, Squash, Pumpkins, Striped cucumber beetle

 

Date: 05/05/2002