No, parrots cannot eat cassava. Cassava is very toxic to parrots.
Why Parrots cannot Eat Cassava?
Cassava roots, peels, and leaves should not be consumed raw due to their high levels of cyanogenic glucosides, Linamarin and Lotaustralin. When these glucosides are broken down by linamarase, a naturally occurring enzyme in cassava, they produce hydrogen cyanide (HCN). Hydrogen cyanide (HCN) is very toxic to parrots. Not only parrots but for human and other animals too.
Cassava varieties are usually classified as either bitter or sweet, with the former having higher toxic levels of cyanogenic glucosides. Sweet cultivars can contain up to 20 milligrams of cyanide (CN) per kilogram of fresh roots, while bitter ones may contain up to 1 g/kg.
During droughts, the presence of these toxins in cassava is especially high. Just 25 mg of pure cassava cyanogenic glucoside, which contains 2.5 mg of cyanide, is enough to kill a rat.
Long-term consumption of cassava with excess cyanide can lead to acute cyanide intoxication and goiters, as well as ataxia (a neurological disorder causing difficulty walking, also known as konzo). It has also been connected to tropical calcific pancreatitis in humans, leading to chronic pancreatitis.
If we see neutritional value of cassava, it contains high level of sugar which is also bad for parrots.
All data collected from USDA.
Additionally, cassava has low amount of microneutrients. So, on basis of neutritional value, cassava is still big no.