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How PICS Bags work …

How PICS Bags work …. Key facts about insect respiration. Insects require oxygen Have high metabolic rates. UNKNOWNS. How much O 2 does the cowpea bruchid consume?. Do O 2 and CO 2 affect feeding?. Developmental stage differences in susceptibility ?. Where do bruchids get their water?.

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How PICS Bags work …

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  1. How PICS Bags work …

  2. Key facts about insect respiration Insects require oxygen Have high metabolic rates

  3. UNKNOWNS How much O2does the cowpea bruchidconsume? Do O2 and CO2 affect feeding? Developmental stage differences in susceptibility ? Where do bruchids get their water? Normoxia – space bag with mesh Hypoxic – space bag

  4. Normoxia – space bag with mesh Hypoxic – space bag

  5. Healthy 3rd instar bruchid larva Desiccated 2nd instar larva

  6. Methods - Callosobruchus maculatus 1. O2/CO2 concentrations – Mocon head-space analyzer 2. Feeding behavior – Purdue Insect Feeding Biomonitor 3. Sealed containers – septum bottles

  7. Hypoxia or Hypercarbia - Feeding CO2 alone

  8. Hypoxia or Hypercarbia - Feeding O2 alone

  9. O2 consumption and CO2 production O2 consumption and CO2 production per bruchid (first instar larva till adult emergence)

  10. Conclusions - Callosobruchus maculatus The insect uses ~ 8-9ml O2 during development Drop in O2, not rise in CO2, affects the feeding behavior The bruchid larvae are burning carbohydrates Role of water in combination with O2

  11. C6H12O6+ 6O2 6CO2+ 6H2O

  12. C6H12O6+ 6O2 6CO2+ 6H2O

  13. What happens in a PICS bag? Insects infesting the grain draw down the oxygen and raise the carbon dioxide level. The drop in oxygen cause the insects to cease feeding and go into a state of suspended animation. Not feeding means not growing and developing and most important of all, not reproducing. Not reproducing means the population doesn’t expand, which means a serious problem never develops.

  14. Bruchid Population Expansion – Why PICS bags work 1 pair of adults at start of storage 30 days later – 50 pairs 60 days later – 2500 pairs 90 days later – 6,250,000 pairs If you arrest feeding, growth and development and reproduction in the first 60 days or so, a serious problem never develops. PICS bags do that – at low cost, simply, using bags that are durable and manufactured in Africa, without insecticides Bottom line – you don’t have to kill insects to control them!

  15. Thanks especially to • Venu Margam • Dick Shade • Ibrahim Baoua • Susan Balfe

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