Rhynchites weevil (Rhynchites aequatus (Linnaeus))
Adult Rhynchites weevil
Fruitlet showing characteristic feeding damage caused by an adult apple fruit Rhynchites weevil
The apple fruit rhynchites is a local but destructive pest of apples which has been increasing in importance in recent years so monitoring is advisable. Hawthorn is the normal host but apple and occasionally pear, plum and cherry can be attacked.
Adults are readily recognised being reddish-brown and having a typical long weevil snout. During blossom and early fruitlet development, the adult weevils drill small cylindrical holes into the flesh with their rostrum. Numerous holes may be made in one fruitlet, or in a group of adjacent fruitlets, by a single weevil. Feeding can continue till July.
At the base of some holes, single eggs may be laid. These hatch after a week or so and the larva feeds on the surrounding flesh, becoming fully grown in about 3 weeks. They then drop to the ground and eventually pupate in the soil, each within an earthen cell. There is apparently one generation per annum.
Fruitlet damage can be serious and is very characteristic. On apple there may exceptionally be 100 or more holes in a single fruitlet but more likely several or many neighbouring fruitlets will each have a small number of holes, each damaged fruit potentially being down graded.
Attacked apples remain marked and distorted, although the holes tend to close up as the fruitlets grow.
- Before its use was revoked, thiacloprid (Calypso) at late blossom or early fruitlet was shown to give good control of adults and prevents further damage. From 2021, Calypso can no longer be used on apples, but it is possible that another neonicotinoid active, acetamiprid (Gazelle), may offer some control, when applied at the same stage of apple development, although this has not been fully explored.
- It is probable that other insecticides such as indoxacarb (Steward or Explicit) are also effective but the efficacy of different products has not been explored.
- Fatty acids (Flipper) has an EAMU approval on apples and is recommended to control apple blossom weevil, so it is likely that it would offer incidental control of rhynchites weevil when applied for blossom weevil.
- Sprays of other broad-spectrum insecticides that control adult weevils are also likely to be effective if applied at this time.
- Use of synthetic pyrethroid insecticides should be avoided as they are harmful to the orchard predatory mite Typhlodromus pyri and other natural enemies.
- If effective control measures are not applied, the apple fruit rhynchites weevil can build up to high levels and cause serious damage (> 50% fruits infested).
- It can be very destructive in organic orchards, where there are very few options available to control the pest.
Insecticides approved for use on apple that are likely to offer incidental control of apple fruit rhynchites weevil adults. No products have a specific label recommendation for the pest.
Choice of insecticides – efficacy factors
|Active ingredient||Trade name (examples)||Class||Recommended by the manufacturer for control of –||Safety to Typhs|
|deltamethrin||Decis Forte etc.||pyrethroid||Aphids, suckers, capsids, caterpillars, codling and tortrix moths, sawfly||harmful|
|fatty acids||Flipper (EAMU 3419/19)||bioinsecticide||Aphids, blossom weevil, two-spotted spider mite||unspecified but generally safe in IPDM programmes|
|indoxacarb||Steward, Explicit||oxadiazine||Codling, tortrix and winter moth caterpillars||unspecified|
Choice of insecticides – Safety factors
|Hazards1||Harvest interval(days)||Max. no. sprays||Buffer zoneWidth (m)|
|Anticholin-Esterase?||Humans||Fish &aquatic life||Bees|
|Key: 1d=dangerous, ed=extremely dangerous, h=harmful, i=irritant|
Control in organic orchards
If effective control measures are not applied, the apple fruit rhynchites weevil can build up to high levels and cause serious damage (> 50% fruits infested).
- It can be very destructive in organic orchards where the only cultural control measure is to manage alternative hosts. However, it seems that although infestations are often associated with adjacent hawthorn, this is not always the case.
- Before 2021, apple fruit rhynchites weevils could be controlled in organic orchards by one or more sprays of pyrethrins (Pyrethrum 5 EC) targeted against adults after blossom. In 2021, AHDB has been seeking an EAMU authorisation for Spruzit (pyrethrins) for use on apple.