eChapters

The application of insecticide to control a particular crop pest should have options of the pesticides, as some may be less effective than other due to various reasons.

Slugs and snails occasionally cause serious damage to seedlings, tender, lowgrowing leafy vegetables; or ripening fruit that are on the ground. Feeding damage, hollowed-out areas, can be found anywhere on fruit, but is usually concentrated near the stem. Slugs leave a tell tale slime trail (silvery trail) behind on the surface of fruit or leaves.

Nereistoxin (NTX) was originated from a marine annelid worm Lumbriconereis heteropoda and its analogue pesticides (table 51) including cartap, bensultap, thiocyclam and thiobensultap have been commonly used in agriculture, because of their low toxicity and high insecticidal activity.

Pyrethrum is the most widely used botanical insecticide. The active ingredient, pyrethrin, is extracted from a chrysanthemum plant, grown primarily in Kenya, Rwanda, Tanzania and Ecuador. Pyrethrum is the powdered, dried flower head of the pyrethrum daisy, Chrysanthemum cinerariaefolium.

Medicines used for controlling insect pests are known as Pesicides which have assumed great importance in today’s high yielding and intensive agricultural system as well as public health programme, all over the world. The term pesticide is an all-inclusive word meaning killer of pests and includes substances used for controlling, preventing, destroying, repelling or mitigating any pest.

Sixteen chemical elements are known to be important for a plant growth, their metabolic activities and survival. These can be divided in to two main groups

Fruit drop just before harvest is a serious problem for various crop varieties. The severity of fruit drop is influenced by several factors but plant stress and premature ethylene production is at the basis of true physiological drop. Stress factors such as late season heat, primary and secondary pest infestation, and nutrient imbalance or deficiency, and heavy summer pruning, all can contribute to drop.

The use of flower inducers stimulates flower growth during the resting year so the tree produces annually. Flower inducers can also increase the number of viable blooms during the natural fruit producing year, for an increase in production. These can also be used on varieties that provide a crop every year, to boost harvest.

Anti-transpirants are usually foliar sprays, although they may sometimes be used more conveniently as dips for immersing the above ground plant parts. Foliar sprays may reduce transpiration in three different ways

Plant growth regulators or phytohormones are organic substances produced naturally in higher plants, controlling growth or other physiological functions at a site remote from its place of production and active in minute amounts. Thimmann in1948 proposed the term Phytohormone as these hormones are synthesized in plants (Thimmann, 1963).

Proper selection of plant health medicines like fungicide, bactericide, antibiotics, algaecide, viricide, nematicide, weedicide, plant harmones and auxins and its application at the correct dose and the proper time are highly essential for the management of plant health. The basic requirement of an application method is that it delivers the chemical to the site where the active compound will prevent the pathogen/pest damaging the plant. 

Seed is a basic input to raise the crop plants. Healthy seeds produces the healthy crop. However, the seed carries different pathogens either externally or sometimes internally in the seed to affect the seed emergence and healthy seedling growth. Therefore, the seed treatment with fungicides/bactericides, based on the infection of the pathogen, is highly essential to counter the attack and infection of these pathogens to the germinating seedlings.

Protozoan parasites are Trypanosomatids of the class Kinetoplastida predominately restricted to invertebrate hosts (i.e. possess a monoxenous lifecycle). However, several genera are pathogenic to humans, animals and plants, and have an invertebrate vector that facilitates their transmission (i.e. possess a dixenous life-cycle).

The algae associated with the plants belongs to the Order Trentepohliales (Ulvophyceae, Chlorophyta). These are filamentous green algae parasitic to higher plants, generally causing minor diseases characterized by negligible leaf spots, but on certain crops, in moist environments, these algal diseases can cause economic injury to plant leaves, fruits, and stems (Nelson, 2008).

Nematodes are multicellular, unsegmented, bilaterally symmetrical roundworms belonging to pseudocoelomates class of creatures. Many of them are parasites of plants. Different crops species are susceptible to several species of plant parasitic nematodes which limits the yield and quality of the food harvest. Root-knot nematodes (Meloidogyne spp.), foliar nematodes (Aphelenchoides spp.), root-lesion nematodes (Pratylenchus spp.) reniform nematodes (Rotylenchulus spp.) and other ectoparasitic nematodes are the important nematodes species to infect the crop plants.

Plant viruses cause severe crop losses worldwide. Conventional control strategies, such as cultural methods and biocide applications have limited success at mitigating the impact of plant viruses.

It is used in the control of bacterial leaf spots, blights, and cankers mostly on fruits crops and ornamentals. The Bordeaux mixture, however, can cause burning of leaves or russeting of fruit such as apples when applied in cool, wet weather. The phytotoxicity of Bordeaux is reduced by increasing the ratio of hydrated lime to copper sulfate. Copper is the only ingredient in the Bordeaux mixture that is toxic to pathogens and, sometimes, to plants, whereas the role of lime is primarily that of a “safener.”

A same active ingredient are available in the market with different trade name and are the product of different companies. These may also differ in their formulation and hazard class (table 7), the knowledge of which is necessary in the plant disease management in view of their effect on the pathogen, ecosystem and environment.

Development of fungicide resistance in a fungal disease pathogen is a major concern for some of the important diseases in their management. This can be overcome by designing of fungicide use strategies to manage the threat of fungicide resistance.