Scouting for pepper weevil in field peppers

Pepper weevil is a pest that is likely unfamiliar to most Ontario field pepper growers. It has been found in Ontario previously (https://onvegetables.com/2010/06/01/pepper-weevil/) and there have been reports of its presence in 2016. As it can be a very serious pest of peppers, it is advisable for all pepper growers to monitor for the pest in their crop. Pepper weevil can affect both field and greenhouse pepper crops, but this article will focus on scouting and management in the field.

The insect

• Adults are small weevils, 2-3.5 mm in length (Figures 1 and 2).
• Difficult to detect the pepper weevil adults through crop scouting if it is present at low levels
  (unless using pheromone traps).
• Eggs are laid in the fruit wall, leaving a dimpled scar (Figure 3).
• Larvae grow and develop inside the pepper fruit; pupae form inside the fruit (Figure 4).
• New adults create an exit hole and leave the fruit.

Scouting

Signs of pepper weevil infestation include egg-laying scars (dimples) and exit holes and in some cases yellowing calyx and flower and fruit drop. Dropped fruit can be inspected for the presence of larvae, but this is not effective for early detection. Infested fruit often remain attached to the plant and may have no external signs except the egg-laying scar.

Pepper maggots create similar dimpled egg-laying scars on pepper fruit. Pepper maggot larvae can be distinguished by the lack of a head capsule, tapering of the body to a pointed head, and a maximum size of about 12 mm. Pepper weevil have a light brown head capsule and a maximum size of about 6 mm long. See Figure 5 for comparison (pepper weevil larva, left; pepper maggot larva, right).

Figure 5a: Pepper weevil larva (left)

Figure 5b: Pepper maggotl larva (right)

Monitoring for adults with pheromones and sticky traps can be very effective (Figures 6 and 7). Trap kits are available (from Trécé Inc.). A local supplier is Plant Products in Leamington or Ancaster. Traps can be placed in or next to the pepper field. Note that kits come with two different lures – one of each must be used for the trap to be effective.

Lures should be replaced every 4-6 weeks in cooler weather, but every 2 weeks in the heat of summer. Replace sticky traps as needed to maintain effectiveness. Pepper weevils are sometimes strong enough to escape the sticky surface. Although 1-2 traps per acre are recommended by the manufacturer, some success has been seen with two traps per field.

Insecticides registered for pepper weevil control in Canada

Several other registered insecticides used for other field pepper insect pests may have activity on pepper weevil. If you suspect you have found pepper weevil or require more information on monitoring or managing the pest, contact Janice LeBoeuf at OMAFRA in Ridgetown at janice.leboeuf@ontario.ca or 519-674-1699.

Other management practices

It is believed that pepper weevil often arrives in an area as a hitchhiker. Be cautious about moving equipment or supplies from other pepper farms. It can also move on people or vehicles. They are relatively good flyers, so can also move from field to field, possibly feeding on weed hosts in transit.

Cull peppers should be disposed of in a way that will prevent the movement of adults from the waste (eg. burial at least 30 cm deep).

Once harvest is complete, it is a good practice to shred/mow the crop residue as soon as possible and bury the residue by plowing or discing. This will prevent continued reproduction and potential spread of the pest to pepper crops still in production.

Pepper weevil will also feed on related weeds and crops, so it may be advisable to keep fencerows mowed if they may contain solanaceous weeds, especially nightshades. Other solanaceous weeds include horsenettle, jimsonweed, and ground cherry.

Photo Credits:

Figures 1, 4: Alton N. Sparks, Jr., University of Georgia, Bugwood.org

Figure 2: Anyi Mazo-Vargas, University of Puerto Rico, Bugwood.org

Figures 3, 5, 6, 7: OMAFRA