A version of this article was originally posted on the I Say Organic blog http://www.isayorganic.com/blog/an-organic-farmers-diary/
Don’t eat guava during the rains from the commercial market, they are all shot full of chemicals. If you do proceed, cut the guava carefully and look out for squiggly fruit fly larva !
Aman Bagh has 50 Allahabadi Safeda guava trees that are today 4 years old, and we took our first fruit crop this year. I was excited at the first flowering of the guava trees in March 2015, and looked forward to eating the fruit off the trees. On my walks around the farm, as the fruits matured, I would break off a guava and bite into the soft, juicy and sweet fruit. I was in organic orchard heaven, and wondered why fruit farmers sprayed their crops with poison when it was so easy to use organic methods to keep pests away … when reality struck. I spied little white squiggly worms in one guava that I had just bit into, disappearing quickly into the flesh of the fruit. I cut deeper into that fruit, and some more, to find what was going on and was horrified to find almost every other ripe fruit infested with larva. I was at a loss on where this came from, thus commenced my Fruit Fly education.
A cousin of the common housefly, the Fruit Fly species that infests guava in India in called Bactrocera Dorsalis (B Correcta and B Zonata are around too, we leave these details to the zoologists).
Fruit Flies and IARI: I found the information necessary to educate myself on this problem, but the solution needed a lot more time. I was fearful of an entire crop in danger: would I need to cut down these trees so lovingly planted and cared for? I raced to the mecca of Indian commercial agriculture IARI (Pusa) in Delhi. An acquaintance sent me to the sleepy horticulture department, where the scientists I met were nowhere as concerned as I was. I was given a dismissive lecture by a senior expert to forget organic methods as “chemical sprays are totally fine and there is too much fuss about too little”. His recommendations were to spray the recommended pesticides and move on. Hmmm. It was food for thought, but not digestible at all.
I went back to reading as there was no solution at IARI. I discovered the larva develops quickly; the female fruit fly lays eggs into the partly mature or mature fruit by the ‘ovipositor’ in the tail by which she pierces the fruit and deposits her eggs. A female lays over 1,500 eggs in her life cycle of 30 days, and she sits but briefly on the surface of the fruit, so she is extremely. Development of egg to adult takes just 15 days, and a week or so after that for the female to reproduce. Temperatures above 30 Degrees C with humidity are happiness for the fruit fly, and the monsoon is ideal for its propagation. When the infested fruit fall to the ground, diseased & weakened by the larva feeding on the inside, the larva converts to pupa, and quickly matures into adult flies. So the fly is continually reproducing in the shadow of the very same tree whose fruit it destroys. Most farmers don’t see the pupae and fly emerging, they few even understand the fruit fly life cycle or even that the fly is the cause of the larva infestation.
We Know So Little: I didn’t understand the problem, why should I look down on less educated farmers. A complex ecosystem thrives under the peaceful, green foliage of a farm; and we know so little about it. There are all kinds of living beings, invisible and visible, inter-connected to each other and to the trees and other plants in thousands of ways some of which we know and many we do not. That is what I learn each day at my farm after years of daily effort, and I find my lack of knowledge remains breathtaking just like our collective arrogance of thinking we know what to do by implementing short term, reductionist methods like spraying pesticides.
With the rains on us in late June this year, the organic Neem-cow urine repellant concoction (which is applied each week) got washed off and eliminated what little effect it had in repelling the flies. I went by the book and had all the fallen fruit picked up, closed in black plastic bags so that the larvae would die and buried these diseased fruits 3 feet under the ground. But the infestation continued unabated. Little did I know then that the flies had done their bit by the time I found out about them in July – the eggs had been laid, and I could do nothing to win from this onslaught by a more knowledgeable foe fighting for the survival of its species. I did not know then that the farm next door has 300 trees of guava, where the farm hands spray their trees weekly with massive doses of pesticides but are not able to eliminate the fruit flies as they keep emerging from the fallen fruit!
What could I do with my orchard wide infestation? I do not use chemicals, and my organic repellants were a failure. With a burgeoning fruit crop, I had read that pruning the tips of the branches with the flowers in May would have been the only sure shot way to eliminate the larvae. With no time and little knowledge on how to combat the fruit fly (all this action took place in just 2 weeks in July 2014) I took the only way I could find such that these do not reach consumers. I pruned all the fruit of all the 40 trees – hundreds of kilos – and fed them to my cows. Now, I had breathing space to figure out what to do in the next season, a year away.
Guava Crops: Guava has multiple crops – the monsoon fruit in July-August, winter fruits in November-December. The study by an Indian guava researcher in Lucknow who had pruned the flowers off an orchard with 7 year old Guava trees by end May and thus eliminated the monsoon crop entirely, and took a full 80 kg per tree harvest in winter. It seemed theoretically possible to eliminate the monsoon crop flowers if pruned at the right time and thus encourage the tree to flower profusely in September for fruiting in December. Why is there little infestation in winter? Simply because it’s too cold for fruit fly sex! With cold and dry days and nights, the environment is not conducive to reproduction. But I was not yet ready to give up on my Fight with The Fly in the monsoon yet, in which I was as of now the loser though an increasingly knowledgeable one.
Sex Traps: I researched and read more and along with my recent experience made sense of what was recommended by organic and chemical producers and academics all over the world. I discovered PCI’s Pheromone based fruit fly traps sold in India: these female sex hormones attract the male which then enters a fly trap and dies as it cannot figure out how to exit. Voila! No male flies, no copulation, just sexually aroused females flies buzzing around that die pining for sex. The fly in the ointment – as I realized when I practiced this method for this season – was that these pheromones don’t eliminate all male flies; they just reduce their quantity. It takes just one male to service the females and keep the progeny machine going at full speed. These traps work as excellent as advance warning that fruit flies are around, but alas do not do eliminate all male flies. I did not know this in February 2015 when I bought one trap for every two trees (ten times the density recommended); and sprayed the trees weekly with an increased concentration of pest repelling organically made sprays. I hoped for success, but the effort to eliminate flies was doomed from the start thought it would teach me a lot.
For the uninitiated, organic pest repellants (with components like Neem, garlic, green chilies and cow urine and a host of other plants that have a strong odor) are exactly that – they repel pests, without killing them and are of no harm to the consumer. Chemical, pesticides are the very opposite – they leave a toxic residue on the surface and inside the fruit which kills the insects they are sprayed on besides being harmful to the human eating them. In the case of the fruit fly, it has been agreed worldwide that only pesticide-based control is quite useless but in our country the only solution for pesticides is more pesticides.
To my lasting disappointment, our efforts to control the fruit fly did not work. We caught scores of flies in the pheromone traps, and were enthused that we were winning – but it was a false hope. Enough males must have escaped to enable the females lay their eggs in the forming fruits, and on breaking open the fruits we could see that a good 40% of the crop was infested. I yet don’t exactly know when the female lays its eggs – in the flower, or the early fruit, or in the semi ripe, or in the fully ripe fruit – but it was enough to keep us looking with anxiety at the fruits every day. We did manage to send more fruits to the market this year as compared to last (which was not really difficult as we sent zip last year!), but it was simply too much effort and stress for too little return.
Conclusion: The fruit fly wins, and we win. We are wiser after this years’ experience and understand the problem as well as the non-chemical solutions, and have decided to prune the monsoon flowers on 30 May 2016 and wait for the winter 2016 fruit. As of now, we don’t know whether it will work but we will have the satisfaction of having rolled with the punches the little fly landed on us. They will look around quizzically for fruits next June, and on finding none in our orchard buzz back to the neighbor. The cold December weather will dramatically control the fly population in any case, and we will continue to use the pheromone based traps as well as the organic pest repellant spray.
Wish me luck, and hope you get to eat clean and sweet winter guava.
Aman Bagh uses only ‘farm yard manure’ for fertilization, from cow dung from my 10 head of cattle, mixed with leaf compost made from the 700 trees we grow. We also use a homemade pest repellant concoction made from Neem oil and other plants fermented in cow urine, which is generally quite effective in repelling insects from most crops.
There must be a way to deal with the fruit fly on a national mission basis, without causing harm to the environment or the consumer. Here is a possibility, as it seems was done in Japan “All Japanese territories were declared free of the oriental fruit fly in 1985, after an 18-year program of eradication combining insecticide-impregnated fiberblocks or cotton containing the powerful male attractant methyl-eugenol, and the sterile insect (sterile male) technique. Steiner traps baited with a lure and toxicant are also used to monitor the presence and control of the flies.”