Integrated Pest Management Guide

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CRANBERRY GIRDLER, Chrysoteuchia topiaria (Zeller)

Pest Status: Cranberry girdler is a serious pest in cranberry beds, as well as in turf, lawns and young conifer plantings.

Life cycle and feeding habits: Young larvae feed on soft tissues such as crowns, leaves and roots of grasses. Mature larvae feed on the bark of cranberry roots and crowns, girdling or severing the roots in the process. This pest is reported to overwinter as a mature larva wrapped in a silk cocoon covered with soil. Recent evidence suggests that in British Columbia, pupation may occur in fall and pupae may overwinter. There is usually only one generation of cranberry girdler per year but, in warm years, a second flight of girdler moths may occur in late summer. Most moths emerge from the soil and take flight from early June until mid July. They are about 1.3 cm (1/2 inch) long with straw-coloured forewings fringed with silver, and three dots along the outer edge. The moth folds its wings close to the body when at rest, giving it a long, slender appearance, and has a "snout". Eggs are scattered on the trash of the cranberry beds during the flight period. The larvae emerge after 4 days to 2 weeks, depending on temperature. Newly hatched larvae are about 1.5 mm (1/16 inch) long. Larvae mature to 1.3 cm (1/2 inch) after several weeks, and chew on the bark of roots and underground stems, girdling and severing vines. Larvae have three pairs of front legs and five pairs of hind legs. Mature larvae do most of their damage from late August through early September.

Monitoring: Patches of many dead or dying uprights in late summer and early fall may indicate girdler damage. It may be mistaken for mouse damage, but mice nip vines cleanly on an angle without gnawing. Damaged roots and larvae can be found by peeling back dying vines and digging carefully in the upper 5 cm (2 inches) of soil and trash. Girdler larvae leave characteristic brown to orange sawdust-like frass (excrement).

Pheromone traps and walking counts are used to detect and monitor moths. Pheromone traps are placed in the beds in early June. Place traps so that the bottoms are roughly 20 cm (4 inches) above the vine tips. A minimum of three traps should be placed on farms of four hectares (10 acres) or less. On larger farms, one trap per 2 hectares (five acres) is recommended. When placing lures in traps, use disposable gloves and keep gloves from touching any other part of the trap. Girdler traps may be placed side-by-side (but not end-to-end) with fireworm traps. Check traps weekly by counting the number of girdler moths, then scraping them off the sticky floor of the trap or replacing the trap if necessary. Change lures every few weeks, according to the manufacturer's instructions.

It is helpful to walk through the beds on a warm day and count the number of girdler moths that fly up. This will help to identify spots where most egg-laying will likely occur. These walking counts can be done when the probability of observing flying girdler moths is greatest. Moth flight is most likely when windspeeds are low (0 - 9km/hr on the dike and 0 - 6 km/hr in the bed), air temperatures are at least 16 ºC, weather is sunny or overcast, and when insecticide has not been applied for at least 7 days. Walking counts can be done for the first time 1 - 2 weeks after the first girdler moth is caught in pheromone traps. Walk through the bed in a pattern that will allow visual inspection of the perimeter and inner areas. The walking pattern may be a long zig-zag or two circles, one around the edges and one around the middle of the bed. Count the number of girdler moths that fly up as you walk through the vines. Record the location and number of these moths on a map of the bed.

In late August through September, damaged areas of the bed should be inspected for the presence of larvae. On a warm afternoon, roll back the damaged vines and follow roots through the top 5 cm (2 inches) of soil, looking for girdled vines, sawdust-like frass, and the beige-white larvae.

Control: Nematodes can be applied 2 - 4 weeks after peak flight to control young larvae. The recommended rate varies from 1 - 3 billion per acre (2.5 - 7.5 per hectare). Larvae can be drowned by flooding beds in August. Flood water should be deep enough to cover the highest weeds, because larvae crawl up them to escape, and should be left on the beds for 24 - 48 hr. Flooding in August will greatly increase the risk of fruit rot on producing beds. Flood-harvesting in early September may kill larvae that have not yet spun their cocoons and become impervious to flooding.

Older beds with a thick trash layer and little sand tend to have the most serious infestations. Regularly sanded beds (6 mm or 1/4 inch) tend to have fewer girdler problems, probably because the sand covers fungi, moss and small plants on which young larvae feed. Sand may also be abrasive and damaging to larvae. The cranberry girdler is also a pest in lawns and turf. Observe dikes and grass areas surrounding the beds as a possible source of infestation.


Cranberry girdler moth


Cranberry girdler larva	Cranberry girdler pupa

Roots damaged by cranberry girdler	Cranberry vines killed by cranberry girdler