Insects on Pomegranates

1-Borrer

Causal organism Zeuzera pyrina

Description

- Adult: 50to 60 mm wingspans for the female, 35 to 40 mm for the male. The thorax is white and hairy with 6 blue spots. The abdomen is relatively long. The wings are white, sprinkled with small metallic blue spots.
- Egg: egg-shaped, about 1 mm, light yellow to bright salmon.
- Larva: 50 to 60 mm, bright yellow with numerous small black points on each segment. The head and the thoracic plates are shiny black.

Biology

- Host plants: a large number of shrubby species such as apple, pear, plum, cherry, olive, pomegranate (Punica granatum), quince, black currant, currant, Citrus, vine, oak (Quercus), ash (Fagus), willow (Salix), lime (Tilia), plane (Platanus), beech (Fagus), poplar (Populus), maple (Acer), tamarisk (Tamarix), etc.

- Adult: it does not feed and its lifespan is extremely brief, from 8 to 10 days. The female mates soon after it have emerged.

- Fecundity: about 1,000 eggs deposited in clusters on trees, preferably in places where the female can insert her ovipositor (crack, old larval gallery); she can occasionally lay in the ground.

- Egg: embryonic development lasts 7 to 23 days.

- Larva: the caterpillars at first remain clustered in a silken cocoon from which they eventually disperse at dawn or at dusk. They then bore into the tips of branches and shoots, then move downwards to attack the young parts of the tree (twigs, spurs, pouches, central veins and leaf peduncles on certain shrubby species).

The caterpillars generally move about to penetrate lower in the twigs and branches. After several migrations, the larvae attack the larger branches and the trunk, in which they form ascending galleries under the bark, then in the wood. The entry holes of the larvae are marked by small heaps of saw-dust and frass (in the shape of small cylinders) accompanied by sap outflows, particularly visible on the large branches, typically at a stage where the damage is already very advanced.

Life Cycle

- Annual cycle in the French meridional regions. The cycle lasts two years in septentrional regions.
- The adults appear from the beginning of June to August. The young caterpillars can be carried by the wind, attached to a silk thread. This mode of infestation is often predominant in young orchards; it also occurs on trees situated close to hedges and thickets. In spring, the larva continues boring its gallery only in the wood and often in the centre of the branch. Pupation occurs from April to July.

Symptoms

The leopard moth is one of the most important pests of apple and pear orchards in Mediterranean regions (and, in certain countries, of olive). The seriousness of the attacks varies according to the age of the plantations.
- On young trees: 1 caterpillar is enough to kill a tree; 3-year-old trees can lose part of their structure. The attacked trees become extremely vulnerable to wind damage and the central axis system is permanently affected.
- Old trees are sverely damaged, particularly in dry years and on dry ground.
- Healthy trees resist attacks better (favourable influence of irrigation and of a balanced mineral supply).

Control
Nomolt                   50 G / 100 L . W

2- Aphids

Causal organism Aphis spiraecola

Description

- Adult: winged, virginiparous females measure 1.8 mm long; the head, thorax and siphunculi are brown, the abdomen being the same green as the young leaves of citrus fruits; wingless, virginiparous females, are 1.5 mm long, entirely green except for the brownish head and brown siphunculi .

Biology

- A polyphagous species.
- In America, whence the species probably originates, the primary hosts are Spiraea; with Citrus constituting the secondary hosts. In southern Europe (and in North Africa), this aphid is anholocyclic.
- In contrast with other citrus fruit aphids, the green citrus aphid is active from spring until autumn, without a summer diapause. It is thus present at each period of vegetation, in the spring and autumn. It overwinters on shoots as parthenogenetic females.

Life Cycle

- The cycle is continuous in southern Italy, where more than 40 generations a year are reported.

Damage

- Damage is severe because the green citrus aphid colonizes young shoots, buds, grafts and young plants, the development of which is inhibited. Spring-time attacks are the most deleterious.

Foliage is severely distorted. During flowering, an attack causes the flowers to drop off.
In addition to direct damage and the honeydew produced which favours the development of sooty moulds, this pest constitutes a dangerous potential vector of Tristeza citrus fruit virus.
Control
              Aphox              50 G / 100 L . W
        or   Nudrin             75 G / 100 L . W
        or  Mospilan          25 G / 100 L .W