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News and information from UC Cooperative Extension about alfalfa and forage production.
Tractor & Hay bales
by Jess Parsonage
on July 12, 2013 at 9:17 PM
I bought some hay with weevil damage. Can I transfer the weevils back to my ranch by doing this?  
by Larry Godfrey
on July 15, 2013 at 8:15 AM
Chances of moving weevil in this way are very slim. Once the hay is dry and baled, the larvae will perish.
by Bill Wilson
on August 14, 2013 at 8:38 AM
This may be a HERE - THERE thing,  
but Here FD 4 & 5 varieties have very little if any Weevil Damage while FD 7 & 8 varieties have enough damage that the damage can be seen from the road.  
Here being 31ºN & 97º 20' W, Half way between San Antonio & Dallas TX and 10 miles East of I-35
by Larry Godfrey
on August 16, 2013 at 2:29 PM
Interesting. Good observation but I can't offer up an explanation right now. I assume your prime/normal weevil damage period is spring as in California.
by Issac Jahns
on May 2, 2016 at 8:38 AM
Are pyrethrins effective for larval stage control?
by Dusty
on December 28, 2017 at 6:23 AM
Will using goats in the winter plus Entrust in the spring be an organic option for weevil control? Will this have any added benefit to Entrust alone?
Reply by Daniel H Putnam
on December 28, 2017 at 7:59 AM
Close Winter grazing has been found to greatly reduce weevil infestation - so yes this seems to be a good weevil strategy. Timing Us likely important. Watch excessive soil compaction it it starts raining.
by Rachael Long
on January 13, 2018 at 7:53 AM
Weevils lay eggs in the alfalfa stems during winter time. We know sheep feeding on these stems helps reduce weevil infestations. However, I worry about goats causing too much damage to the alfalfa crowns because they are more aggressive feeders. Sheep are more like lawn mowers, so they work well in alfalfa. I've never seen anyone use goats. Entrust is the best material we have for controlling weevils in organic alfalfa, providing about 70% weevil control, which is enough to be economical in terms of protecting hay for good yields.
by Athena Cholas
on June 25, 2018 at 10:18 AM
The article says, "Beneficial insects, including parasitoid wasps, are not present in fields in high enough numbers to prevent economic damage by the larvae." This seems to refer to the numbers of beneficial insects in the spring. Would insectary habitat in alfalfa fields support enough populations of predatory insects in the fall to keep numbers of eggs laid in the winter low? Then the impact in the spring would not be so great.
by Daniel H Putnam
on June 26, 2018 at 4:56 AM
Comment by Rachael Long:  
Alfalfa is an insectary plant in that it has extra-floral nectaries (nectar sources outside the flowers) that attract beneficial insects to help control pests and reduce herbivory. This is likely one of the reasons that there are so many beneficial insects in alfalfa fields (and there’s plenty of pests for predators to feed on too, like aphids too). The only reason that we don’t promote alfalfa in insectary habitat plantings is that alfalfa is also a host of a number of different viruses that are problematic in other crops, such as alfalfa mosaic virus in tomatoes and dry beans as well as leaf scorch in almonds. The issue with biocontrol of alfalfa weevils by parasitoid wasps is that the alfalfa weevils frequently encapsulate and kill the wasp eggs when they’re laid inside the weevil larvae. Generalist predators aren’t effective enough, likely because the eggs are laid inside stems, protecting them. When a big hatch occurs, the predators can’t keep up, resulting in high numbers of weevils in fields.
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