Laboratory Techniques for Rearing Disease-Free Insect Colonies: Elimination of Mattesia grandis McLaughlin, and Nosema sp. from Colonies of Boll Weevils12

Abstract

Mattesia grandis McLaughlin and a microsporidian, Nosema sp., were eliminated from laboratory colonits of the boll weevil, Anthonomus grandis Boheman, by a system of “Unit Integrity” that is adaptable to rearing procedures for different species of insects, makes best use of available labor and facilities, and permits production of the largest possible disease-free colony per period of time. The “Unit” is the most homogeneous grouping obtainable, given the incidence and characteristics of the disease; once the insects have been placed in the unit, they are handled as an entity and are separated from all other such units to reduce danger of cross contamination. The unit used to raise a disease-free colony from weevils infected with the microsporidian was the “Family Unit” because the disease was transmited by transovum passage; selected units were reared through the F₁, generation, and units containing no disease through adults of the F’ generation were considered disease free. The unit used with weevils infected with M. grandis was again the Family Unit, but these larger groups were then divided into subunits and given the less strenuous treatment of 10-day quarantine. The system produced larger numbers of healthy insects more quickly than selection of progeny from single pairs of weevils. It had the disadvantage that it was more susceptible to failure because of its design, although disease elimination was successful in the test.