HortFACT
Identification
The common name of this weevil commemorates both an early insect collector (Fuller) and the first recorded host plant (nursery-grown tea roses, in America).
The adult is 8 mm long, smaller than the white-fringed weevil, to which it is closely related, but rather similar in shape. It is grey-brown, darker on the sides, and there is a distinguishing short, oblique, white line halfway along the body. It is flightless, but has a habit of climbing, so is found on shrubs and small trees as well as low-growing plants. It is most active after dark.
The yellow-gold eggs are cemented together, like the eggs of the white-fringed weevil, in clusters of up to 60. They are tucked into crevices such as the sheathing stipules of clover, new shoots of lucerne, and splits in the bark of vines and shrubs, or between pieces of vegetable litter on the ground. They have even been found blocking the small plastic tubes used for trickle irrigation in farms and orchards. The egg masses are resistant to drought, and when conditions are sufficiently moist they hatch after a minimum of 20 days.
The larvae, or grubs, up to 9mm long, are at first yellow like the eggs, but become white after a few days and creamy-white as they mature. They are legless, and resemble whitefringed weevil larvae in having a pale head partially drawn back beneath the hardened prothorax. They burrow into the soil, where they feed on roots to a depth of 25 cm or more.
Fully fed larvae, called prepupae, move towards the soil surface from July onwards. They have become dense white - no dark gut content is visible. A smooth-walled cell is prepared by rotating the abdomen and lining the walls with mucus secreted from the anus. Since pupation does not take place until November or December, the prepupal period can be quite lengthy.
Eventually the prepupa sheds its larval skin to become a pupa, which is the adult insect in a soft, fragile state, neatly folded and encased in a protective theca (skin). The theca bears some very short, curved bristles and a pair of spines on the terminal segment. These protect it from damage by abrasion which could occur during the 10 days or so of the pupal period when the body is constantly being rotated. After a final moult, and when the cuticle has hardened, the emerging adult tears the cell apart using a pair of cusps (teeth) on the mandibles. These cusps then drop off, leaving a characteristic scar.
Host plants
Fuller's rose weevil is mainly a pest of horticulture. It will fed on almost any garden plant where the soil is not heavy, but shows a preference for roses and citrus. In agriculture it is one of a number of weevils that attack lucerne.
Damage
Adults feed on leaves, young shoots, and buds, so the effects on nursery stock can be severe. Young larvae chew off rootlets and root hairs, and older larvae eat well into main roots. This type of damage impairs water uptake, resulting in stunted growth and even death of the plant during dry spells.
Distribution
Fuller's rose weevil originated in the warm temperate climate of South America, but has spread to most climatically comparable parts of the world, largely through human agency. Adults can cling tightly to rough surfaces, and are inconspicuous; eggs are well hidden, and can survive dry conditions. This weevil is thought to have arrived in New Zealand via Australia, and was well established in 1940. It now occurs throughout the North Island and in the Nelson region.
Life cycle
| Egg |  |
| Grub | |
| Pupae | |
| Adult | |
| Month | |
| Note: Coloured bars indicate periods of peak activity in each of the life cycle stages | |
There is only one, extended generation each year. Adults and larvae are present at all times, but egg laying and hatching reach a peak in early autumn. Pupation and adult emergence are confined to summer. Reproduction is parthenogenetic, i.e., eggs of the next generation are produced by unmated females.
B. M. MAY