• Potato aphid

  The potato aphid ( Macrosiphum euphorbiae ) is of North American origin, but is these days distributed throughout the world. It is a highly polyphagous [...] s species with a preference for Solanaceae (particularly potato), but has also been identified on more than 200 plant species from more than 20 families [...] Retarded growth and defoliation reduce yield. Plant sap is rich in sugars, but has a low protein content. Aphids therefore need to extract large quantities

• Bacterial soft rot, bacterial stem rot

  Erwinia carotovora subsp. carotovora or Pectobacterium carovora is very common, but does not often reach epidemic population densities. It can survive as epiphytic [...] wounds, for example pruning wounds. It cannot infect healthy green leaves, but can grow in senescent leaves and from there grow through the petiole to the

• Circular scale

  Chrysomphalus aonidum is a tropical species, native to the Oriental region but it has been dispersed widely in tropical and subtropical parts of the world [...] lower and central parts of mature trees. Circular scale prefers the leaves, but in high infestations it may spread to fruits, stems and trunks, and may cause [...] single pair of wings. First-instar nymphs are 0.3 mm long and have legs, but soon settle to form circular, initially white scales. Circular scales reproduce

• Gooseberry

  mostly green, but there are also red (varying to purple), yellow and white varieties. The wild berries are smaller than cultivated kinds, but do have a nice

• Glume blotch

  Primary infection is mostly by ascospores or conidia on the oldest leaves, but seed transmission is also possible. The germ tubes can infect the leaves of [...] are responsible for wind dispersal of the fungus over longer distances, but inside an infected crop the conidia cause secondary infection by splash dispersal

• Grapes

  varieties of Vitis vinifera grapes, but only a few play an important commercial role when it comes to the production of wine, but also table grapes. Still, cultivars

• Woolly apple aphid

  rots or apple canker. Woolly aphid does little direct harm to mature trees but the sticky masses of “wool” may contaminate leaves and fruits and can be a [...] forms. Sometimes a few wingless egg-laying females are produced in autumn but their eggs do not develop further. Adult viviparous (wingless) females of [...] produced in summer. Winged egg-laying females are produced in early autumn but their eggs do not develop. Contrary to the situation in America, South Africa

• Pierce's disease of grapevine

  dwarfing. Leaves and flowers appear early and remain on the plant longer, but fewer and smaller fruits are produced. In plums, the first symptoms are irregular [...] band. In the beginning, only a few leaves per branch are showing symptoms, but later the growth stops and the plants die, usually within a few years. Citrus [...] and look stunted. Twigs and branches die and the foliage becomes thinner, but the trees don’t die of the disease. Olives: Scorch symptoms and desiccation

• Pine processionary moth

  annual but may extend over 2 years at high altitude or in northern latitudes. Development lasts 6 months under the most favourable conditions, but the fourth [...] or other wood-boring insects. In mature forests, trees are rarely killed but significant losses occur in volume growth. Defoliation damage and the presence [...] affected. These effects occur not only when the caterpillars are present, but also during the following summer because of the persistence of allergenic

• Long-tailed mealybug

  Pseudococcus longispinus occurs naturally in tropical and sub-tropical regions, but these days it is widespread throughout the world. The range of host plants [...] Pseudococcus longispinus is less extensive than that of the citrus mealy bug but it nevertheless encompasses many species of (ornamental) crops (e.g. croton [...] the yield. Flowers and fruit often drop off. Plant sap is rich in sugars, but low in proteins. In order to gain an adequate intake of protein, mealybugs