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Insect Pathology

Insect Pathology. Prof. Abdelwahab A. Ibrahim Entomology Department, Faculty of Science, Benha University. PROTOZOA. Microspora.

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Insect Pathology

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  1. Insect Pathology Prof. Abdelwahab A. Ibrahim Entomology Department, Faculty of Science, Benha University

  2. Prof. Abdelwahab A. Ibrahim PROTOZOA Microspora • All Protozoa are single-celled eukaryotes and they range in their interactions with insects from commensualists and mutualists, to plant and animal pathogens vectored by insects, to acute insect pathogens. • Of some 14,000 described species of Protozoa, about 500 are pathogens of insects • Groups: Ciliophora, Sarcomastigophora, Apicomplexa, Microspora. • Reproduction is asexual by multiple or binary fission. The fusion of two gametes forms a zygote which divides repeatedly. • Infection: Chronic rather than lethal caused by ingesting spores then penetration of digestive tract. Nosema Spores V. necatrix Malamoeba

  3. Prof. Abdelwahab A. Ibrahim PROTOZOA Microspora • Protozoa kill the host only at very high levels. • Spores have a polar capsule which, after ingestion and germination develops into a tube that can penetrate gut cell walls. • The liberated spores are highly resistant. Transmission of spores is possible through the eggs. • Culture: In live insects only. • The most important protozoans for biological control. • Nosema:. Nosema locustae infects a wide range of grasshoppers. • Vairimorpha: Vairimorphanecatrix is a broad spectrum agent which is infectious to many Lepidoptera. • Malamoeba: mainly known as a contaminant of laboratory cultures of locusts. Nosema Spores V. necatrix Malamoeba

  4. Prof. Abdelwahab A. Ibrahim NEMATODES • Nematodes are unsegmented, worm-like organisms with a tough outer cuticle. Nematodes are larger than other entomopathogenic organisms and can usually be seen with the naked eye. • They can act as vectors* for entomopathogenic bacteria. • There are eight or nine orders associated with insects. • Adults are bisexual. They develop through four larval molts before reaching maturity. • Generally grow in the host and develop in the environment, in both aquatic and terrestrial habitats. • MERMITHIDAE • Subclass Penetrantia, family Mermithidae; a large group of obligate parasites. • These invade through the cuticle at the second larval stage and develop to the fourth larval stage filling the host body cavity. This shows as a swollen abdomen. • Larvae emerge after rupturing the host cuticle. Mature in surrounding soil and water • It can be cultured in live insects or in macerated liver. • Host range: Romanomermis culicivorax can kill early instar mosquito larvae. Other mermithids sometimes attack locusts and grasshoppers.

  5. Prof. Abdelwahab A. Ibrahim NEMATODES • SECERNENTIA • These are free living saprophytes and do not kill insects. Exceptions are from the genera Steinernema (=Neoaplectana) and Heterorhabditis, known as rhabditidnematodes. • Free-living third instarrhabditid larvae are attracted chemically to susceptible hosts. They penetrate through the mouth or anus, enter the haemocoel* via the gut wall. Some may enter directly through the cuticle. They release highly virulent bacteria (Xenorhabdus spp.) into the haemocoel. • Nematodes feed and develop on host tissues and bacteria. Third stage infective larvae containing bacterial inoculum emerge from the cadaver 10 days after penetration. The larvae need free water to disperse in.

  6. Prof. Abdelwahab A. Ibrahim Nematodes pathogenic to insects • Pathogenic Nematodes are microscopic, nonsegmented worms that occur naturally in soil all around the world. Once they are released, the nematodes seek out host insects and enter their prey through body openings, injecting them with lethal bacteria, then feeding on the resultant "goo". The nematodes reproduce and their offspring feed on the insect cadaver and emerge to seek out new hosts. The endo-toxin generally results in death of the host insect within 48 hours. • Nematodes are easy to use. They are shipped in a dry powdery clay formulation that is easily mixed with water. The solution can be applied using a watering can; hose end, backpack, or pump sprayers; or through irrigation or misting systems. Always release early in the morning or late afternoon when temperatures are cooler and away from direct sunlight to avoid exposure to ultraviolet rays and the drying effects of the sun. It is good to pre-moisten the soil before application and to water the area where application was performed afterwards. Soil should be moist, but not saturated.

  7. Prof. Abdelwahab A. Ibrahim Nematodes pathogenic to insects • Generally, 10 million of Beneficial Nematodes will effectively treat approximately 900 sq. ft. of conventional garden rows or up to 2500 sq ft broadcast. Release nematodes every 3-6 weeks or until infestation subsides. • Nematodes can be stored in a refrigerator (do not freeze!) for up to 2 weeks, but it is best to use them as soon as possible, because they are somewhat perishable. If they start to smell bad, they're on their way out.

  8. Prof. Abdelwahab A. Ibrahim NEMATODES

  9. Prof. Abdelwahab A. Ibrahim NEMATODES Nematodes Heterorhabditidae Wuchereria bancrofti or Filaria Insect parasitic nematode, highly magnified. Steinernematidae

  10. Prof. Abdelwahab A. Ibrahim Thanks

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