Bees do fine in conjunction with modern crops as long as they have sufficient reservoirs of wild habitat to shelter in and feed upon when the crops aren't in flower.

Hence why the study found bee declines as corn production went up: bees don't even feed upon corn, GM or non-GM. Cornfields are wildlife deserts.

It has more to do with larger and larger farms with less and less fences and hedgerows between farms. In the days before tractors, the average farm.

The above report also says that the average size of a farm went from 147 acres in 1900 to 441 Acres in 2015. Rural population has dropped as a percentage of total US population, but the number of people living on a farm has dropped even further. Many farms no longer have people living on them, the workers on those farms commute from "Urban Clusters" or small farms that produce very little produce for sale but the farmers on those farms feed their families (i.e. more a "Hobby Farm" then a farm set up to sell farm products). Thus you have a lot of 50 acres or less farms, the number of those farms have stayed about the same since WWII, it is the farms of 50 to 1000 acres that have seen a decline in numbers, while the farms of over 1000 acres have increased in number and size.

http://www.agday.org/media/factsheet.php

Tractors only surpassed horses on farms in the 1960 census, thus till the 1950s the horse remained more important then the tractor, but that all changed in the 1950s.

Thus in areas like the Central Valley of California, the Southern Cotton, Rice and Soybean crops and the Midwest Grain fields, where you have millions of acres of farmland of one crop. That crop is planted and harvested by contract workers, with a smaller number of employees working between planting and harvesting. This has lead to larger and larger farms in these areas:


It is this change since WWII, accelerated since the 1970s, that is killing the wild bees. Wild bees need something in flower all year around, or at least from spring to frost. If you plant five crops, as was common in 1900, that and a flower garden would provide such wild bees flower to feed off all year around. This was the pattern before WWII. It started to change in 1900, speed up after WWII, and then accelerated even more since the 1970s.

People forget the the Horse was NEEDED on the farm till the widespread adoption of the three point hitch post WWII. The Three point hitch was invented in 1939, but WWII delayed its adoption. The three point hitch finally permitted Tractors to plow between the rows of crops AFTER the crop has been planted. Such plowing was needed but only able to be done with a horse PRIOR to the three point hitch.

With the horse no longer needed on the farm (Post WWII) tractors could do the job horses use to do. As farm became larger, larger tractors would cut down time plowing, spraying and harvesting thus cutting costs. To use those larger tractors that required larger fields, cutting back on fence lines and hedgerows. Thus less places for wild bees to live and to find flowers to live off of.

Thus the problem with wild bees is the larger and larger farms we have today. People will oppose my solution to this problem, increase regulations on farms over 50 acres. Including forbidding farming near creeks and streams (a problem in my home State of Pennsylvania, farming to the side of such creeks and streams have lead to massive influx of fertilizer into the Susquehanna River and the Chesapeake bay causing problems in the bay (The Susquehanna River is the single largest river that flows into the bay). Similar problems exists for the other rivers flowing into the Chesapeake Bay. Forbidding farming within six feet of such streams may be all that is needed.

Similar restrictions will help other bees. Some compensation MAY have to be paid, but denial of PLOWING or PLANTING in some areas of farms MAY be done if it can be shown no overall loss of value of such land. The better option would be to take over such streams of water and turn them over to the state with a restrictions that it can not be sold without federal permission. This would cost more than just a regulation forbidding plowing but would make it clear WHAT is NOT open to farming or other activities that harm such waterways (Hunting and fishing would be permitted, cattle and other animals could graze, provided trees along the waterways are protected).

The Federal Government has to do something to protect wild bees and the above is by far the best method, but it requires commitment to solving the problems of wild bees not just month service and I suspect the later is what we will hear when we need actual actions.

Please note, the report I cite, ignore an observation reported by Admiral Richover in a speech in the 1950s. While US production per crop per field had increased for decades by that date and were higher on larger farms then smaller farms, total production of crops per acre was much higher in smaller farms than larger farms. The reason for this was simple, smaller farms were noted for planting three or more crops in the same field. Total production of EACH crop was less then on the one crop per field larger farms, but since you had three compatible crops in the same field, you had almost three times the TOTAL crop production. I.e. if you planted Beans, Corn and Pumpkins in the same field, you cut out anything by hand hoeing of weed, but while the Corn Production per acre was less then Corn production on larger farms, larger farms did NOT produce the beans and pumpkins in the same field. These three crops had been planted together on small farms since the days of the First Americans. More labor intensive but higher TOTAL production of all THREE crops per acre. Such farming techniques are NOT profitable at the present time, given the huge farms sheer volume of the one crop they do produce, but such productively is the product of the same system that is killing off the native bees.

My point is it is NOT farming that is the problem, but the tendency to larger and larger farms that are hurting small hobby farms AND the bees.