Angela Tucker's List: Alfalfa Weevil

• braconid wasp Microctonus aethiopoides (= aethiops) is the  only one that attacks adult weevils
• well established throughout the alfalfa-growing areas of the upper Midwest and  northeastern United States
• one of the most important parasitoids responsible for maintaining alfalfa weevil  at or below economic levels
• M. aethiopoides lays a single egg directly inside the body cavity of  the weevil. The larva that hatches from the egg then feeds and completes its  development internally in 22-26 days. There are no external signs of parasitism  until the larva is fully grown and it forces its way out of the back end of the  weevil. The wasp larva spins a whitish silken cocoon and pupates in the soil or  under debris. An adult wasp emerges 6-9 days later. M. aethiopoides overwinters  as first instar larvae inside hibernating weevils.
• first generation females attack and lay eggs in the surviving overwintered  weevil adults (spring population) that are actively laying eggs in mid-May. The  second generation wasps attack newly emerged weevil adults (summer population)  in late June.
• two generations per year that are well synchronized with the adult weevil's  activity
• effect of M. aethiopoides on the alfalfa weevil population results not  only from death of the adult weevils themselves, but also by reducing the number  of eggs a female weevil lays. Parasitized alfalfa weevils cease oviposition  within three days; male weevils are castrated shortly after parasitization.  Although the parasitized summer generation weevils will survive until the  following spring, they are unable to reproduce and hence contribute nothing to  the alfalfa weevil population
• Effective conservation can be achieved by using degree days for timing sprays to  avoid insecticide applications during the periods when the adult parasitoids are  active. Leaving uncut "refuge" areas of alfalfa allows parasitized weevils to  survive. These and other cultural practices can enhance the beneficial  activities M. aethiopoides provides in biological control of the alfalfa weevil

6 more annotations...

• use of degree day accumulations, average alfalfa stem length, and numbers of  weevil larvae on 30 stems collected randomly in the field allows accurate  management decisions to be made on this important first-cutting pest.
• Damage will appear on the leaves, growing tips, buds and new shoots of the  alfalfa plant. Leaves become skeletonized and the resulting bleached out plant  has an appearance resembling frost damage. Field samples for alfalfa weevil  should be made at least every 7 days,
• Select the appropriate management table based on the degree day accumulation for  your area.

1 more annotation...