Question
QUESTION: I have a number of gambles oak trees on my property and was interested in harvesting the acorns for food. However, last year when  I did just that there were too many worms in the nuts to eat any. Do you know at what month or growth stage of the nut the adult lays eggs on the nut so I can come up with a good management scheme to deter this pest? I live in Castle Rock, Colorado and the oaks I have are about 10 to 15 feet tall ( the tall gambles rather than the scrub types).

ANSWER: The adults mate during the early summer months, high in the oak trees. Once the females are fertilized they will deposit their eggs in tiny chambers in the new soft-shelled acorns that have been drilled with their amazing snout. When the eggs are deposited, the female will close the opening with a fecal plug to protect the eggs. The plug dries, turning white in color, keeping the eggs and larvae safe from predators. When the eggs hatch the larvae feed on the soft insides of the acorn until the nut
drops from the tree. Once the larvae have matured they will drill an exit hole out of the acorn and burrow in the soil near where the acorn has fallen. Interestingly, most larvae remain in the soil for up to three years before they pupate during the spring. New adult acorn weevils appear in early summer, crawling up the base of the oak tree to begin feeding and mating.

I would try using a soil applied insecticide called Bayer Advanced Tree and shrub Insect control. This is a systemic insecticide and should be transported by the roots into the acorns and when the weevils bore into the acorn or the larvae feed on the acorn  they should be killed.

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QUESTION: do you have a organic or non-systemic insecticide that might work since I intend to eat the acorns?

Answer
Do not know of an organic that will work on there insects--try an insecticide called Orthene. It will not get into the meat of the acorn and should control the insect--the problem will be spraying at the right time when the adults are present. So I would treat at ten day intervals for say three sprays and this should cover the adult part of the life cycle.  The other problem will getting complete coverage of the spray on all the foliage if the trees are tall. That is why the soil applied was recommended. Since acorns take two years to mature and the concentration in the acorn then selves will be very very small there will not be enough insecticide residue to harm you. The Bayer product is labeled for fruit trees and the fruit is edible, I do not think the soil applied will be a problem in eating the acorns.