Plum Injurious Insects

A Lecture To ToT trainees ( FFS)

By Mr. Allah Dad Khan

Provincial Coordinator IPM KPK

MINFAL Pakistan

Fruittree leafrollerArchips argyrospila

Symptoms

Leaves of plant rolled and tied together with silk webbing; feeding damage to rolled leaves; defoliation of plant; silk webbing may also be present on fruits and fruits may have substantial scarring from feeding damage; larvae wriggle vigorously when disturbed and may drop from plant on a silken thread

Peach twig borerAnarsia lineatella

Symptoms

Death of shoot tips; feeding damage to fruit, usually at stem end; larvae are dark brown and white with a black head; adult insect is a gray-brown moth

Mealy plum aphidHyalopterus pruni

Symptoms

High levels of infestation may cause stunted vegetative growth; black soot mold developing on leaves and branches; insect is small and soft-bodied, green in color and covered in white, mealy wax

Green fruitwormVarious

Symptoms

Large holes chewed in leaves and fruit; pale green caterpillars with white stripe down middle of back present on leaves and fruit

Scale insects (White peach scale, San Jose scale)Pseudaulacaspis pentagonaQuadraspidiotus perniciosus

Symptoms

Scale insects cause damage by feeding on twigs, branches and fruit on peach trees, injecting toxins into the plant as they do so; if the infestation is heavy, gumming may occur on the bark and twigs or entire branches can be killed; insects are flattened discs, or "scales" with no visible legs; scales produce a white waxy coating which eventually turns black (black cap stage)

European earwigForficula auricularia

Symptoms

Mature trees generally tolerate damage well; if damage is caused to shoot tips of young trees then growth may be stunted; shallow, irregularly shaped areas may be present on fruit surface where insect has fed; insects are brown and shiny with a pincer-like structure at the end of the abdomen; can reach 1.3 cm (0.5 in) in length

Oriental fruit mothGrapholitha molesta

Symptoms

Wilting shoot tips ("flagging") caused by insect feeding; insect frass may be visible around entry holes burrows in fruit which cause the fruit to be soft, mushy and discolored; adult insect is a small gray moth; larvae are initially white with a black head but turn pink with a brown head as they mature

Plum trees are often attacked by aphids and the first signs are young leaves curling up, this is often referred to as Plum Leaf Curl. They are not normally discoloured just curled. If you uncurl the leaf the aphids will be seen inside - small green, white or light brown insects. By themselves they probably won't cause too much damage but often they secrete a sticky juice which attracts unwanted diseases.

APHIDS 

The picture above shows the damage done to plums by the plum sawfly (Hoplocampa flava). From the outside the plum looks OK, may be a small brown mark on the skin but nothing more. But inside, the plum is completely inedible. You may also notice one or two small hardened drops of resin on the fruit which are the tree's response to being attacked.

In spring the sawfly emerges from the soil and lays eggs on the blossom of plum trees. When the plums develop the little caterpillars eat their way into the centre of the plum and feed off it as the plum develops.

PLUM SAWFLY

Plum CurculioConotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae)

Plum Curculio

Plum curculio larva, left, and pupa

 Plum curculio spring feeding damge to cherry

Plum curculio egg and oviposition damage

Dried sap produced by plum curculio feeding and oviposition wounds on apple

Plum Curculio

Plum curculio oviposition scars on apple

Internal plum injury caused by plum curculio

Plum curculio late season feeding damage to apple

Winter Moth The signs to look for are small

green caterpillars on the leaves, buds which fail to develop and leaves with holes in them. This pest is the Winter Moth and will normally become apparent in late March to May. The first indication will be tiny caterpillars on and around fruit and leaf buds. They may spin silken threads and hang from the tree twigs. They then grow into larger caterpillars and will eat leaves, buds and almost all parts of the foliage.

Scale Insects

Picture of Lecanium Scales on a plum tree

There are many forms of scale insects which attack a variety of plants but one in particular can be a problem with plum trees, it is named the Lecanium Scale. The picture below shows just how scary looking this pest is but, although serious if left to its own devices, it is not impossible to control. At maturity they look like pea-sized growths which are purple-brown on stems and young branches.

Plum pocket

Plum fruit affected by Plum Pocket

Relatively unknown in garden cultivated plum trees in the UK, Plum Pocket is becoming increasingly common. The symptoms are quite unusual and hard to mistake for any other pest or disease. Young fruit begin to to appear longer than normal and slightly larger, this normally becomes visible around mid June time. The next symptoms are white marks on the skin of affected plums, this is a fungus forming. Soon after the plums will begin to wither and die. Normally only around 50% of the plums are affected.

Shot hole Borer  The picture below describes

the symptoms very well. Round holes in the bark of the tree are visible, most frequently in the main stem. Repeated attacks result not only in holes in the bark but the bark begins to lift off the surface of the inner wood. The Shot hole Borer is most common on plum, apple, pear and cherry trees

WASPS ON PLUM TREES

Wasps can eat and disfigure plums and sometimes the damage is considerable. There have been many contraptions and devices developed over the years but, so far, the evidence is that none of them has any significant effect in reducing wasp activity.This includes jam jars full of sugary liquid which can trap a few wasps but the numbers are so insignificant that they can be considered useless.

The latest device is a false wasp nest which is intended to scare other wasps off. We can find not a shred of evidence that this works.