Entomology 10
Insectivorous Plants		and Insects
	Sharpshooter
	as Vectors of Plant Pathogens

I. Mechanisms to "trap" insects (associated with an attractant)

1. Sticky exudates (attractive to insects) to entangle them -- fly catcher
2. Modified structures (spots of color or nectar) to capture them -- pitcher plants
3. Modified leaves (color and nectar-like substance) to entrap insects -- Venus fly trap

II. Digestion - glands with enzymatic fluid to digest insects (not exoskeleton)

III. Absorb nutrients through plant tissues

Insects as Vectors of Plant Pathogens

I. Diseases transmitted by insects

1. Nonpathogenic diseases
   1. Toxins from salivary secretions
   2. Oviposition wounds
2. Pathogenic diseases
   1. Viruses
      1. Sucking insects (aphids, leafhoppers)
      2. Chewing insects (beetles, grasshoppers)
   2. Bacteria and mycoplasmas
      1. Sucking insects (leafhoppers)
      2. Chewing insects (beetles)
      3. Chewing-lapping insects (honey bees)
   3. Fungi
      1. Chewing insects (beetles)
      2. Contamination of body (beetles)
   4. Nematodes - beetles

II. Method of Transmission

1. Mechanical - through contamination of mouthparts or other body parts.
   1. No biological relationship with pathogen
   2. Fireblight of apples and pears
2. Biological - specific (more or less) relationship between insect and pathogen.
   1. Nonpersistent (aphids)
      • Ex. Cucumber mosaic virus
   2. Persistent (aphids, leafhoppers)
      1. Circulative, non-propagative (no reproduction in insect vector)
         • Ex. Pea enation virus by aphids
      2. Circulative, propagative (reproduction in insect vector)
         • Ex. Aster yellows by leafhoppers

III. Insect-Plant Disease Relationships

1. Transmission of fireblight (mechanical)
2. Transmission of Dutch elm disease (biological)
3. Transmission of aster yellows (biological)

IV. Food for thought -- Are there advantages to serve as a vector of plant or animal (e.g. malaria) pathogens/parasites?

NO READINGS IN GULLAN AND CRANSTON.

Reference: Evans, H. E. 1984. Insect Biology. Addison-Wesley, Reading, MA.

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