Lowbush Blueberry Fact Sheet

• Introduction
• Description
• Biology
• Damage
• Monitoring Technique
• Action Threshold
• Control

Introduction The Blueberry Sawfly, Neopareophora litura (Klug), and two species of Pristophora occasionally cause severe defoliation in lowbush blueberry fields. The following information is intended to help growers recognize this insect, and to assess and control infestations.
Description Sawflies are a type of wasp (Hymenoptera). They belong to a group of wasps which can generally be distinguished from other wasps by there being no constriction between the thorax and abdomen. The adult blueberry sawfly is about 4.5 to 5.0 mm in length. The colour varies from yellowish brown with black markings to entirely black. It is not likely that the grower will observe the adult stage.	Blueberry Sawfly adult Click picture to enlarge
The larvae are caterpillar-like. They are green in colour with a clear line down the back. They are 9 to 11 mm in length. Sawfly larvae differ from caterpillars in that they have 'legs' on all but the first abdominal segment while most caterpillars have prolegs on the third to sixth abdominal segments and on the last abdominal segment. The sawfly head is also more distinct than most caterpillars.	Blueberry Sawfly larva Click picture to enlarge
The pupa is enclosed in rough silken cocoon. The cocoons are oval, and are light to dark brown in colour.
Biology The insect passes through winter in a prepupal stage as a cocoon, located in the upper 5 to 8 cm of soil. Pupation occurs early in the spring. The adults emerge from early to late May. The females are parthenogenic, that is, they can lay viable eggs without mating. There are very few males in the population. Egg laying takes place during the first 4 days after the adults emerge. Each female can lay about 30 eggs. Eggs are laid singly in the leaf buds of the blueberry plant. The eggs hatch in 5 to 11 days. First instar larvae feed within the leaf bud. On expanded leaves, the larvae begin feeding on the leaf edge and work toward the midrib. The larvae go through several molts during their 4-week feeding period. They then drop to the ground and burrow into the soil, where they spin a cocoon. There is only one generation per year. There are two other species of sawflies that feed on blueberry. They belong to the genus Pristophora. They are similar in appearance to the species described previously. The larvae can be distinguished by the white stripe on either side of the back. The biology of these species is also similar to that of the blueberry sawfly. These two species are less common in occurrence.
Damage The larvae can do considerable damage to blueberry plants if they are present in large numbers. The greatest amount of damage is done by the older larvae. Most outbreaks occur in the crop year. Sawfly larvae are present at bloom time. In severe outbreaks they also feed on blossoms.	Blueberry Sawfly damage Click picture to enlarge
Monitoring Technique Blueberry sawfly larvae can be monitored by sweeping the foliage with a 30 cm diameter insect sweep net. Crop fields should be sampled weekly during May to the end of June. It is suggested at least three samples per field in fields of 5 hectares or less be taken. Each sample should consist of 25 sweeps. For larger fields an additional sample should be taken for every five hectares. Sampling should be done on warm sunny days. Action Threshold An action threshold has not been established for this insect. Based on research done at the University of Maine, it may range from 3 to 5 larvae per sweep. This would equal 75 to 125 per sample. If sample numbers are found in this range, the field should be checked for signs of defoliation and control measures taken if necessary. Control Several parasites of the blueberry sawfly have been noted. They are all Ichneumonid wasps. These wasps lay their eggs in the sawfly larva. They do not kill the larva until after it has formed the cocoon. These parasites help to keep the populations in check. They would not control an outbreak in time to reduce damage to the crop. If populations reach the levels discussed under 'Action Threshold', an insecticide should be applied. Consideration should be made for the safety of pollinating insects when deciding to control this insect, as most out breaks occur during the bloom period. Control products and rates of application are listed in the lowbush Blueberry Protection Guide ACC 1011.

Note:
Nova Scotia growers can purchase sweep nets through the Blueberry Producers Association of Nova Scotia (BPANS). They may also participate in the annual blueberry insect survey.