Kiwifruit Pests

Like many other fruit-bearing trees, kiwifruit vines suffer from a variety of pests that can partially or completely ruin your crop.

Some of these pests are bacterial, others are fungi, so the defenses will have to be planned differently and case-by-case. We will try to analyze the most common kiwifruit pests and try to offer good advice to prevent them, or get rid of them if already present.

Kiwifruit Bacterial and Fungal Diseases

Armillaria Root Rot (Armillaria mellea)

Type: Fungal Infection

Cause:This fungal infection is very often facilitated by a persistently wet soil, whether it be by over-watering or by naturally occurring humidity.

Symptoms: You will often see the bark turn to a blackish color, with white mycelium (fungi) strands underneath or near the roots. The vines will lose support and eventually collapse

How to cure and prevent:

  • Do not overwater kiwifruit vines: if soil is always damp it’s a sign it is overwatered.
  • Before planting a vine, make sure you remove all roots with more than 1cm in diameter (they may be infected with the fungus).

Bleeding Canker (Pseudomonas syringae)

Type: Bacterial infection

Cause:This bacterium spontaneously infects kiwifruit vines and can overwinter on them

Symptoms: Typical red-brown cankers on branches that may or may not produce a red secretion. Blighting of the canes, plants wilt

How to cure:

  • If you have an infected branch, cut it at least one foot below the edge of the last canker
  • The incidence of the disease can be somehow (but not totally) mitigated by protecting the vine from freezing injuries

Crown Gall (Agrobacterium tumefaciens)

Type: Bacterial infection

Cause:This bacterium may spontaneously infect the vine through a wound

Symptoms: Stunted growth, small leaves, poor yield and open canopy. Galls may or may not be present (if they are, it’s a telltale sign of the disease, but not all plants develop them, or they may be too small to see)

How to cure and prevent:

  • You can reduce the incidence of this disease by preventing injury to the plant
  • If already infected and galls are present, they have to be surgically removed

Bacterial blight (Pseudomonas spp.)

Type: Bacterial infection

Cause:This bacterium may spontaneously infect the vine through a wound

Symptoms: Small yellowish spots on leaves (especially after raining), petals develop an yellow-orange discoloration and may present brown holes, especially in the zone covering the flower buds

How to cure and prevent:

  • You can reduce the incidence of this disease by preventing injury to the plant
  • There is currently no good known method to cure the plant after the infection

Phytophthora root and crown rot (Phytophthora spp.)

Type: Oomycete (fungus) infection

Cause:Fungus growth is favored by soils that are constantly damp, or by watering so frequently that the vine does not have time to dry completely

Symptoms: Red-brown discoloration of roots and crows (they are only visible when you cut them in two). Vines generally show a much lower yield and may collapse without warning. leaves are small, shoot growth is stunted

How to cure and prevent:

  • You can reduce the incidence of this disease by properly draining the soil and avoiding dampening it for long periods of time
  • Applications of fungicides may prevent the disease

Botrytis Fruit Rot (Botrytis cinerea)

Type: fungal infection

Cause:Fungus growth is favored by very wet conditions in pre-storage periods (up to a month before harvesting). Post-harvest conditions are also important, since most infections show their symptoms during this period

Symptoms: Gray, moldy fruit that may show a watery and dark green pulp. It generally manifests during storage of fruit and may very negatively affect the yield. Fungal growth can occasionally be seen at the stem.

How to cure and prevent:

  • You can reduce the incidence of this disease by properly draining the soil and keeping fruit dry beginning one month before harvest and during bloom
  • The most effective non-organic method is to spray fungicides post-harvest (Fludioxonil 8-16oz single application, or Fenhexamid 24 oz single application)
  • The most effective organic method is to let the “cut” end of the stem dry completely before storing and freezing the harvested fruit.
  • This fungus resists very cold winters and storage temperatures down to -1°C, so it can overwinter

Kiwifruit Nematodes

Some roundworms (root knot nematodes), when present in too high populations, can cause root damage.

Type: nematode

Cause:Nematode growth is favored by the presence of other plants in the vicinity that produce a favorable habitat. Kiwifruit vines that are irrigated too sparingly are more susceptible to root damage

Symptoms: Root galling (typical symptom).

How to cure and prevent:

  • You can reduce the incidence of this disease by removing broad leaf weeds in the vicinity of the vine
  • The most effective non-organic method is to spray broadcast treatments in october/november, the year before planting (with Metam Sodium or 1,3-Dichloropropene).
  • The most effective organic method is to let the “cut” end of the stem dry completely before storing and freezing the harvested fruit.
  • This fungus resists very cold winters and storage temperatures down to -1°C, so it can overwinter

Kiwifruit Insects and Mites

Omnivorous Leafrollers (typically Platynota stultana)

Type: insect

Cause:Overpopulation due to absence of predators or other population control mechanisms

Symptoms: Dark yellow-brown caterpillars with dark heads that feed on fruit causing damage

How to cure and prevent:

  • Parasitic wasps and tachinid flies are natural predators
  • A post-bloom treatment with Bacillus Thuringiensis Kurstaki (low application rate every week) is quite effective, but warranted only if there was caterpillar damage present in the previous harvest, or if early signs of caterpillar presence are detected

Boxelder Bug (typically Boisea trivittata)

Type: insect

Cause:Vineyards are affected almost always when very close to coastal regions

Symptoms: bud and fruit drops, fruit malformation. The insects have dark oval bodies (adult) with red wing undersides. The small, deeply red, crawling insects are nymphs

How to cure and prevent:

  • Esfenvalerate, applied in early flower budding is very effective

Armored Scales (Hemiberlesia rapax, Hemiberlesia lataniae, Aspidiotus nerii)

Type: insect

Symptoms: scale insects on the vine, leaves and kiwifruit. They feed on the plant fluids, reducing plants’ vigor and possibly yield. Scales may also form on fruit, reducing its commercial value

How to cure and prevent:

  • Various species of Aphytis wasps, minute pirate bugs, green and brown lacewings, and small lady beetles are all natural predators for biological control
  • The most effective non-organic method is Methidathion (one application per year).
  • The most effective organic (not everywhere) method is narrow range oil sprays.

For more information:

1 – http://www.ipm.ucdavis.edu/PMG/selectnewpest.kiwifruit.html