toxicogenic insects by mian nasir mehmood

7/31/2019 Toxicogenic Insects by MIAN NASiR MEHMOOD

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NASIR MEHMOOD

06-Arid-109

M.Sc (Hons.)

PLANT PATHOLOGY


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Plant Diseases & Toxicogenic Insects Plant diseases Mainly caused by Pathogens.

Insects along with direct impact on agricultural and horticultural crops

Also act as Vectors of plant pathogens.

Relationships between plant pathogens and their vectors are complex.

In absence of Pathogens insects causing plant diseases

indirectly.

No. of v.destructive plant diseases are caused by toxic substances

Introduced into plant tissues by sucking insects.


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Some imp. Terms related to Toxicogenic Insects WALTER CARTER ( Pineapple Research Institute of Hawaii ).

Review Article. Injuries To Plants Caused By Insect Toxins.2

Toxicogenic Insects

Insect Species produces toxic metabolites in plants .

OR

Species of insects capable of secreting phytotoxic substances

Toxiniferous

Condition which express the active toxic stage of a toxicogenic insect


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Toxemias / Phytotoxemias / Toxicoses

Refers to the Group of plant diseases caused by Insects Toxins.

Stigmonose

Term used for diseases characterized by local lesions caused by insect

punctures e.g. lesions on apple due to feeding of rosy apple aphid.


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Major differences b/t Toxicogenic insects &Viral diseases

Diseases by Toxicogenic insect Viral diseases

Cause by phytotoxic secretions or

toxins

Cause by Virus

Toxins. non reproductive in plants Can reproductive in plants

Disease can be recover Disease cannot or rarely recoverable

Disease cannot transmitted by Grafting Can transmitted by Grafting

Disease control is possible by insect

control

Disease once establish cant control


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How Toxicogenic Insects Cause Disease?....

By injecting toxins via salivary secretions which effects..

By disturbing the working of some hormones

By increase or decrease in quantity of certain enzymes

By direct and rapid killing of cells in and around site of feeding

By increase acidity of cell sap

BY destruction of cell structures


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EXAMPLE

Action of toxins in case of Leaf Spot Diseases of Carnation/plants.

Initially the insect injects some toxic metabolites/substances into wound

It may be an acid or of enzymatic nature

Cause increase of oxidizing enzymes in cells where toxin reach. Enzymesinterfere with nutrition of cells

By destroying the chlorophyll and other biochemical changes.

Result in death of cells appears as.spots


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HOPPERBURN IN PLANTS

leafhoppers suck fluids from plants with their piercing sucking mouthparts.

Inject saliva that contains a compound toxic to plants.

Toxic & feeding clogs the conductive tissue of plants

Resulting in an accumulation of starches

This accumulation causes a relative nitrogen deficiency resulting in

yellowing or injured leaves.

First symptom of potato leafhopper injury as a V-shaped yellowing at the

tips of the leaflets (top photo), commonly referred to as "hopper burn"."

As injury progresses, the leaves may turn purple or brown and then die.

Severely injured plants also are stunted and bushy in appearance because the

internodes stop growing normally.


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Important diseases caused by Toxicogenic Insects

Hopper burn of potato & Alfalfa.

Insect galls

Psyllid yellows of potatoes

Froghopper blight of sugarcane

Mealybug wilt of pine apple

Leaf spots of carnation

Green spotting of pine apple


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Hoppers & Hopperburn on Alfalfa Pine apple Mealybug and Wilt


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Potato leaf hopper and hopperburn disease


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Potato Psyllid adult Potato Psyllid nymph
http://www.ag.ndsu.edu/archive/entomology/ndsucpr/Years/2010/August/12/Figure3.gifhttp://www.ag.ndsu.edu/archive/entomology/ndsucpr/Years/2010/August/12/Figure2.gif


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Galls cause by apple gall midges


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THANKS

toxicogenic insects by mian nasir mehmood

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