Prays citri

Citrus flower moth

Whiteflies suck the sap from leaves and from tender shoots, provoking leaf drop and producing honeydew on which saprophytic fungi develop which favour the growth of sooty mold, a blackish fungal encrustation which dirties the plants.

Aphids suck the sap from the leaves and from tender shoots. Some species provoke curling of leaves. Moreover they damage flowers, stimulating their drop and producing honeydew. They are dangerous because some of them are vectors of virus, like tristeza.

Soft scales, margarodid scale, mealybugs suck the sap from leaves and from tender shoots, producing honeydew which dirties the fruits.

Armored scales suck the sap from leaves and tender shoots without producing honeydew. The infected branches are liable to lose their leaves and twigs may dry up, sometimes in such a bad way as to cause the decline of the plant. The fruits infested are discarded. The psillid Trioza erytbreae is the main vector of greening, a disease caused by a phloem-limited bacterium.

Beetle larvae attack roots, branches, and the trunks of trees, provoking their decline. Adults nourish themselves with leaves.

Fruitflies provoke punctures on the fruits in order to deposit their eggs from which larvae are hatched, provoking fruit rot and carpoptosis.

Ants nourish themselves on leaves and honeydew produced by other insects. They spread the attack of other insects and interfere with their natural enemies.

Moths damage flowers and fruit set. They cause miners and curling up of leaves. They make holes and miners on the fruit, sometimes stimulating fruit drop.

Among the pests there are the nematodes, microscopic vermiform organisms some of which are parasites of plants. The pathogenic nematodes of the citrus trees, living in various areas, are different (Lo Giudice, 1986), but only a few have some economical importance (Inserra and Vovlas, 1977). The most wide spread in the world is Tylenchu-lus semipenetrans (Citrus nematode). Mature female is a sedentary parasite which penetrates with the anterior part of its body into the outer cortical cells of the roots of the citrus plant, leaving on the outside posterior part of its body, where the definition semi-endoparasite derives from. The posterior part of females' body and their eggs are protected by a gelatinous mass produced by them. Males are not parasite forms. The species is bisexual, but can reproduce by parthenogenesis (Dalmasso etal., 1972). They prefer well-oxygened soils but they can live on various types of soil and on species different from citrus like olive, grape and persimmon as there are different biotypes (Duncan and Cohn, 1990). The cycle from egg to egg lasts 6-8 weeks. The non-specific symptoms induced by parasitization are a reduced growth and vigour of the plant and production of under sized fruits. There are some physical, chemical and agronomic means to control this nematode, but the best control is prevention, avoiding the contamination by using, for the new plantings, the nematode free plants and using a preplanting located chemical treatment, where necessary. In case of infestation on plants in production the chemical means adopted are based on the level of infestation thought dangerous, choosing among the suitable nematocides.

Pest management techniques

The use of insecticides has evolved over time. We have passed from using hydrocyanic acid fumigation, mineral oils, tobacco, powders of pyrethrum to the organophosphorus esters, carbamates, chlorinated hydrocarbons, pyrethrin group, botanical insecticides like nicotine and rotenone, insecticides from microbial origin to follow with the development modifiers like moulting hormones, juvenile hormones and with behaviour modifiers like antifeedants and pheromones. The research continues to find other means of innovation and above all substitutes of chemical ones. Apart from insecticides, other means of control have had an evolution. For this reason we are now able to distinguish various means of control.

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