Most of the studies in Offenberg’s review are on weaver ants (Oecophylla), a tropical species which lives in trees and weaves ball-shaped nests from leaves. Because weaver ants live in their host trees’ canopy, near the flowers and fruit that need protection from pests, they are good pest controllers in tropical orchards.
All farmers need to do is collect ant nests from the wild, hang them in plastic bags among their tree crops and feed them a sugar solution while they build their new nests. Once a colony is established, farmers then connect the trees that are part of the colony with aerial ‘ant walkways’ made from string or lianas.
After that, the ants need little, except for some water in the dry season (which can be provided by hanging old plastic bottles among the trees), pruning trees that belong to different colonies so that the ants do not fight, and avoiding insecticide sprays.
The review shows that crops such as cashew and mango can be exceptionally well protected from pests by weaver ants.
One three-year study in Australia recorded cashew yields 49% higher in plots patrolled by ants compared with those protected by chemicals. Nut quality was higher too, so net income was 71% higher with ants than with chemicals.
Similar studies in Australian mango crops found that ants could produce the same yield as chemical control, but because the ants were cheaper, and fruit quality better, net income from mangoes produced with ant protection was 73% higher.
Those crops are special cases in which the ants are vastly superior. But in many other cases ants are as effective and much cheaper than chemical options. Different species of ants are suited to protecting different types of drops. Weaver ants require a canopy, other ants can protect crops without a canopy.
I hope more farmers adopt ants to help protect their crop yields.
Related: Pigs Instead of Pesticides – Why Don’t All Ant Species Replace Queens in the Colony, Since Some Do – How To Make Your Own Pesticide with Ingredients from Your Kitchen – Another Bee Study Finds CCD is Likely Due to Combination of Factors Including Pesticides (2013)