Eggplant, Pepper, & Tomato XXIV-1

Colorado Potato Beetle

Whitney S. Cranshaw & Jay D. Donahue

Colorado Potato Beetle

Field Biology and Identification

Colorado Potato beetles (CPB) have stout, oval bodies that are striped. The stripes are slim and alternate between yellow-orange and black on the wing covers. Eggs are laid in clusters and are a bright orange in coloration. There are four larval, or immature, stages of development that can be readily distinguished from one another by the width of the head and the size of the body. Also, coloration changes from a brick red to a pale orange as the insect matures. Young larvae are much more sensitive to insecticides than older larvae, so correct identification is essential. The fourth larva digs down into the soil three to six inches deep to pupate. Depending on temperature, the adult emerges within two to three weeks.

Adult females mate and lay eggs in clusters on the underside of potato leaves. A single female is capable of laying around 300 eggs in a one month time period. Most eggs are laid in mid-June, but could be sooner if weather and temperature permits. Eggs hatch in four to sixteen days. There is usually one generation each year, but two may occur. In mid August, adults burrow into the soil six to twelve inches deep to overwinter.

Plant Response and Damage

Infestation often occurs at the edge of the field by adults, which generally do not fly over a quarter of a mile when searching for new food sources. Dispersal within the field is often limited as well, and may result in a clustering or concentration of the beetles.

Both adults and larvae feed upon the foliage of the potatos. Adult and immature CPBs feed upon the plant in a similar fashion. Feeding occurs at the edge of the leaf and often ends with the complete destruction of the leaf. Newly emerged stems may be clipped off. Complete defoliation is possible if the beetles go unmanaged, and yield may be reduced by 50 percent or more. However, potato plants can withstand some defoliation without affecting yield. This is dependent upon the growth stage of the plant.

The vegetable crop may not be the target plant of the CPB. Adults may become a contaminant of Midwest peas if solanaceous weeds (such as nightshade) is present within the field. Volunteer potatoes may cause the same problems. Improved sanitation practices generally eliminate these problems.

Management Approaches

Cultural Control

The use of trap crops (such as nightshade) can be used to lure the beetle away from the vegetable crop. Any beetle found upon such trap crops should be collected and destroyed. Early-maturing varieties are best for trap crops.

Crop rotation is a relatively easy control method, as long as the ensuing crops are not within the tomato family.

Host Plant Resistance

Hairy-leaved varieties of eggplant as trap crops may be used since they is less favored by the CPB for feeding preferences.

Biological Control

CPB eggs are often eaten by both ground beetles and lady bird beetles. Larvae are preyed upon by the two-spotted stink bug Perillus bioculatus. A parasite for the larvae is a tachinid fly. Young larvae can be controlled with Bacillus thuringiensis, or "bt," (san diego and tenebrionis strains). This is another reason to be able to properly identify both the insect and the life stage!

Chemical Control

The egg and the pupal stages are not affected by chemical controls. Adults are highly resistant to most marketed products. Larval stages are the most susceptible to chemical sprays, and while management practices should try to avoid the fourth larval stage (this is the stage in which 70 percent of the immature feeding occurs), spraying should not occur until after egg hatch.

Note: The following products are listed for eggplant, and may or may not be listed for other crops. Check product label for usage restrictions.

Product List for Colorado Potato Beetle:

Insecticide	Product per Acre	Preharvest Interval, Remarks
M-Trak	2–3 qt.	A strain of Bacillus thuringiensis tenebrionis is genetically modified to improve persistence on leaves. Larvae only. Smaller larvae are much more susceptible than are older larvae.
Sevin XLR+^1, 4F^1Sevin 80S^1Sevin 50W^1	1 qt 1.25 lb 2 lb	(0 days) A carbamate insecticide (carbaryl). The 80S, 4F and 50W formulations are highly hazardous to bees. Some rotational restrictions. May be used with sprinkler irrigation. 12-24 hour reentry interval proposed.
Thiodan 50W^1 Thiodan 3E^1, Endocide 3E^1	1 lb	(1 day) Some rotational restrictions on root crops. 2 applications maximum per year. 48 hour reentry interval proposed. Chlorinated hydrocarbon insecticide (endosulfan).
Pounce 3.2E^RAmbush 2E^RAmbush 25W^R, Pounce 25W^R	8 fl oz 12.8 fl oz 12.8 fl oz	(1 days) Proposed 24 hour reentry interval. Pounce and Ambush are pyrethroid insecticides (permethrin). Acutely toxic to fish and other acquatic organisms.
Asana XL^R,^1	5.8–9.6 fl oz	(7 days) Proposed 24 hour reentry interval. Pyrethroid insecticide (esfenvaralate). Some rotation restrictions with root crops.
Vydate L^R	1–2 qt	(1 day) High leaching potential. Carbamate insecticide (oxamyl). 48 hour reentry interval.
Admire 2F	16–32 fl oz	21 days. Soil treatment that may be applied pre-planting, at-planting, or post emergence. May be applied in drip or trickle irrigations systems. Chloronicotinyl insecticide with systemic activity. Flea beetle and psyllid activity.
Provado 1.6F	3.75 fl oz	1 day. Contains same active ingredient as Admire. Maximum 18.75 fl oz/per season, with minimum 5 day intervals between treatments. Flea beetle and psyllid activity.
Kryocide 96W	8–16 lb	14 days. Inorganic insecticide (sodium aluminofluoride) with stomach poison activity.
Capture 2E^R	2.1–6.4 fl. oz.	7 days. Eggplant only. Maximum 12.8 fl. oz./acre/season.
Assail 70WP	0.025 – 0.05 lbs a.i. (0.6 – 1.1 ounces)/A in 5 gal/A by air or 20 gal/A by ground
^RRestricted use pesticide. ^1Labeled for chemigation.
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: Colorado potato beetle, Eggplant, Tomato, Pepper, Insects

Date: 08/19/2002