Insect of the Month - Colorado Potato Beetle

 
  Hort Snacks - July 2017
Download 902K pdf file ("HortSnacks-July2017.pdf")PDF
(902K)
     Subscribe to our free E-Newsletter, "Agri-News" (formerly RTW This Week)Agri-News
This Week
     Hort Snacks HomeHort Snacks Home
 
 
 
 Leptinotarsa decemlineata

Crops Affected: Plants in the Solanaceae (potatoes, tomatoes, eggplant, solanaceous weeds)

Life Cycle:

  • Adults are 10mm by 7mm (1/3 inch by ) somewhat rounded beetles with black stripe markings running the length of the back overlaying the pale yellowish colouring
  • Adults overwinter in the soil where crops were previously grown
  • Beetles move upwards as soils warm in the spring – typically emerge in late May or early June
  • Beetles seek out and feed on host plants, starting to mate after several days of feeding
  • Females lay yellow to orange eggs on the underside of leaves in clusters of approximately 30
  • Larvae are humpbacked and reddish-orange with 2 rows of black spots along the side of their body
  • The entire period of egg laying occurs over a couple of months
    • Larvae emerge and feed on the plants for 2-3 weeks until pupating in the soil
  • New adults appear after approximately 3 weeks and feed for a short time before entering the soil for overwintering
  • Typically single generation per season
Symptoms:
  • Adults and larval stages feed mainly on the foliage of the plant
  • Irregular holes in leaves and leaf margins – complete defoliation can occur with high populations
  • Some stem feeding may also occur
  • Presence of adults, larvae or eggs in the field
Colorado Potato Beetle larva
CPB Adult
.......................CPB Adult
.....................................................................................................Photos by Brent Elliott

Monitoring:
  • Sampling random plants throughout a field, with counts and size estimates of larvae that are present can give some indication of population levels
  • Economic thresholds have not been consistently established; however the presence of 20 large larvae (later instar) per plant may be considered a general threshold for mid-maturing crops (based on a sample of at least 40 plants).
  • Producers should also take into account other crop stress factors and the level of feeding and defoliation that is occurring when determining when to start control measures
Management:
  • The use of registered insecticides is a common management practice
    • Care should be taken to rotate between different chemical families, to avoid to build up of resistance (resistant populations have developed to many common chemicals)
    • Use spot treatments to control adults in the early season if possible and systemic larval control products as required (if thresholds are reached)
  • Regular rotations to non-host crops can be an effective tool in keeping populations low and in keeping new populations at the edges of fields
  • Biological controls can be used, however native predators are generally ineffective
  • Control Solanaceous weeds in non-host crops, to make crop rotations more effective
  • In smaller plantings, children can be unleashed with rocks and a jar to collect adults and crush egg clusters and larvae – how effective this is at actually reducing beetle populations is difficult to estimate
 
 
 
 
Share via AddThis.com
For more information about the content of this document, contact Robert Spencer.
This information published to the web on June 29, 2017.