Biological Control ~ Backfiring in India (Weed Control with Insects) ~ an insight
Prickly Pear (Tamil: Sappaathik Kalli) Opuntia dillenii, is a menacing weed on road sides and field bunds in India and Sri Lanka and it is one of the earliest success stories for use of bio-control agents.In this case, a mealy bug (Tamil: Maavup Poochi) was used. This bio-control agent is called, Dactylopius tomentosus.
Based on this success story, many countries (Australia, Cuba etc) used different bugs (Species of Dactylopius on different species of Opuntia). Nearly five decades later, in India, we still find Opuntia dillenii coming back to life and still the insect (Dactylopius tomentosus) clinging on to its dear life.
Opuntia is too strong and comes back to life, in the very same place where it perished after being sucked sapless by the bug. Science has learnt a certain lesson here..Nature does fight back !.
The second lesson that Bio-control Advisors learnt from this particular insect is that once the main host (in this case Opuntia) is not available aplenty, then the bio-control can also turn into a pest damaging crops. A very valuable lesson learnt, as mealy bug today is a serious threat on commercial farms / plantations of Papaya, Rose and also to home garden plants like Hibiscus, Custard Apple, Guava, Crotons, Plumeria, Mussaenda, Poinsettia etc.
This bug has a white wooly covering and pesticides cannot penetrate the cover the kill the insect at later stages. Dichlorvos is the only compound (with its vapourizing action) that is found effective to clean by swabbing. This guy (Mealy bug) is sedantary and cannot move by itself. Therefore, it attracts ants by secreting a syrupy concoction, liked by ant brotherhood, who for returning the favour, transport the mealy bugs from one host plant to another. Hence, as an additional precaution, ant powder is applied at the base of host plants to prevent this transport getting anywhere nearer.
This is how a successful Bio-control agent has turned into a pest !
Who said Bio-control agents are host specific..?
Ask our papaya growers and rose farmers in India !
2 comments:
Sir
Vanakkam & Greetings
The observations on Mealy bugs-aka Maav Poochi is most useful and well documented with evena Cactus pic.Most appreciated.This is a nuisance in home gardens esp after Monsoon-frequently cause damage and they have affected my Hibiscus and Tulasi plants-Used all methods esp Neem-Oil spray with a hand sprayer after washing of the bugs -residues with a cloth -hand ; and now trying a Bio S Power spray from the T'Nagar Chennai Plant Store.Not many know about how to control Mealy bugs and it took long to understand -Used Bio S Spray only recently and it is a weekly spray.(These white fuzzy spots and growth repeatedly come back and earlier lost many plants) .Wish to discuss on Plants and pest control -Thanks Rgds CaptTR(Retd)
Hi Captain..Sorry for the belated feedback..I am not a regular blogger. I use FB regularly though. Valliappan Kalaiyappa is FB name and you are welcome to connect.
For mealy bugs..(1) in Spots: Swabbing and swiping away is the best with cotton plugs or ear buds, dipped in chemicals / neem spray compounds (2) for large areas, neem won't work: Dichlorvos (NUVAN or VAPONA is Trade name 1 ml/L water spray will work) (3) For both the above, ant powder needs to be applied on soil (around base of plants)-both affected and nearby good ones, to prevent ants from "transporting" mealy bugs from one plant to another. Goodluck. Valliappan
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