Did one or both sides of the cold war plan to strategically attack the others' food production?

There is good reason to believe that such a strategy was considered ... at least until the 1970s.

The strategic use of defoliants arose before the Cold War. From the Agent Orange Wikipedia entry, that mind set seems to have sustained for a few decades before a treaty was signed in the mid 1970's.

Several herbicides were discovered as part of efforts by the US and
the British to develop herbicidal weapons for use during WWII.
¹ {snip} In 1943, the U.S. Department of the Army
contracted the University of Chicago to study the effects of 2,4-D
and 2,4,5-T on cereal grains (including rice) and broadleaf crops.
From these studies arose the concept of using aerial applications of
herbicides to destroy enemy crops to disrupt their food supply.

Over a thousand chemical tests were run for the next few years in the US. The idea of destroying crops didn't die with the end of WW II.

The British were the first to employ herbicides and defoliants to destroy the crops, bushes, and trees of communist insurgents in Malaya during the Malayan Emergency

Given the development and use demonstrated by at least one side, it is reasonable to conclude that such a strategy was on the table for the first few decades of the Cold War. While I don't have a source for the USSR side, the development of nuclear, chem, and bio weapons, and plans to use them on both sides suggests that both sides left the options open to use them, and had plans in case they chose to. (Defoliants/herbicides are a sub set of bio warfare). The Soviet biological warfare program dates to the 1920's, and there was a herbicidal component to that program as well as the disease spreading program.

it is interesting to note that President Ngo Dinh Diem of South Vietnam (in 1961) asked the United States to conduct aerial herbicide spraying in his country. In August of that year, the South Vietnamese Air Force conducted herbicide operations with American help. {After a significant policy debate} ... in November 1961, President Kennedy authorized Operation Ranch Hand, U.S. Air Force's herbicide program in Vietnam. (Same source as above; paraphrased).

It is chilling to consider the various means that were researched and considered usable against one another by the powers in the Cold War.

While I don't have an 'end date' that mind set saw considerable political push back in the 1970's. ("lessons learned" from Viet Nam, so to speak).

The Environmental Modification Convention, was opened for signature and ratification on May 18, 1977, and entered into force in October 5, 1978. The convention prohibits the military or other hostile use of environmental modification techniques having widespread, long-lasting or severe effects. Many states do not regard this as a complete ban on the use of herbicides and defoliants in warfare but it does require case-by-case consideration.

So were herbicides still on the table up until the wall came down? Nothing to confirm or deny so far, but likely those plans got shelved during the period of summits and armaments reduction talks of the 1980's. (Will try to find a confirmation and edit if I do).

¹ Judith Perera; Andy Thomas (Apr 18, 1985). "This horrible natural experiment". New Scientist, April 18, 1985: 34–36.

Arguably yes, but one doesn't have to look for exotic biological weapons when ordinary nuclear weapons could be used. The whole logic behind "counter value" targeting was to have a second-strike that could survive the initial onslaught (dispersed bombers and submarines) and strike back at civilian targets (since hitting back at military targets might not be as helpful, especially since some of the enemy's fixed nuclear targets - airbases, sub pens, and missile silos, would be empty at that point.)

A recently-declassified list of US Cold War nuclear targets suggests that "agricultural centers" were on the list. Presumably the same would have been true of Soviet nuclear targeting as well.

http://www.foxnews.com/politics/2015/12/24/declassified-cold-war-files-reveal-america-s-extensive-nuclear-target-list.html

https://www.nytimes.com/2015/12/23/us/politics/1950s-us-nuclear-target-list-offers-chilling-insight.html