‘Take care of difficult problems, while they are still easy; Do easy things before they become too hard.
The Master never takes on more than he can handle, which means that he leaves nothing undone.
The Master expects great difficulty, so the task is always easier than planned.’
Lao Tzu
‘Master gardener no need bug spray’
Les
Ok. Everybody knows it’s not a good thing to spray food with poison. It’s bad for the environment, bad for the farmer and bad for the consumer, so why is nearly all our food grown with chemicals?
The sad fact is that if you grow something good to eat, there is every chance that something else will come along and eat it, with no consideration for whom it belongs to. I have often tried the old maxim: ‘One for de cutworm, one for de crow, one to rot and one to grow’ with little or no success. It can work in some places, but the last time I tried it was in far north Queensland and I planted hundreds of sweet potato and cassava, enough to feed every wallaby, bandicoot and bush turkey for miles if they were allowed to grow and still be plenty left over for me. The bush turkeys had ripped them all out and destroyed them by the following morning.
Unfortunately, growing ‘organically’ doesn’t mean just not spraying; there are a whole suite of techniques and approaches that must be applied unless you want to see other creatures benefit from your efforts. The most rational and effective approach is called Integrated Pest Management, or IPM. It is based on sound knowledge of ecological principles and an understanding of life cycles and population dynamics. Some basic principles are as follows.
1) Understanding environmental factors
Probably the most important factor is knowing what environmental conditions are the best for the plants you want to grow, or better still, knowing which plants suit your particular environment. These factors include full sun or shade, different types of soil, nutrient needs, water requirements, temperature limits, humidity, wind protection and air circulation. Get some or all of these factors wrong and the plant will be weak and susceptible to disease. A classic example is outbreaks of spider mite in glasshouses; they usually occur when humidity is low and can be prevented or controlled by maintaining high humidity. Fungal diseases are prevented or minimised with good circulation and drainage.
Timing is crucial. Grow the right plant for the right time of year. Trial and error can help identify when pests and diseases are most likely to be a problem so that efforts can be concentrated in the most favourable season, getting the maximum effect for the least effort. Another thing to consider is the type of environment; some things such as rice grow well in monoculture, but for many reasons large monocultures are an ideal environment for pests to thrive (see my comment at the end of Jeff’s blog here).
Diverse systems, which mimic natural environments, are more likely to be stable with minimal chance for population explosions of pests or disease. Humus and compost rich soils are known to be richer in beneficial organisms and naturally occurring compounds which inhibit many pathogens. Biological pest control, where a pest is targeted with the release of a known predator, has proven to be very effective in some situations, but we can design our gardens to include habitat and food supply for naturally occurring predators. Many plants in the Umbelliferae or carrot family (coriander, dill, Queen Anne’s lace, etc) have flowers which attract and provide nectar for omnivorous beneficial insects such as ladybugs, parasitic wasps and predatory flies. The sunflower family, Compositae (also called the Asteracea family), is another group of plants which can help attract beneficials. Frogs are voracious insect predators and small ponds in a garden provide habitat for them and other beneficials such as dragonflies. Many nectar eating birds are also insect eaters, so nectar rich flowering shrubs can also help.
If you consider and plan with all these factors in mind, you shouldn’t have too many problems. If you do have problems with particular plants, my approach is to grow something else. This may not mean abandoning something altogether, it might mean trying a different variety. I have examples of different types of citrus growing side by side, some devastated by grasshoppers and sooty mould while others are completely unaffected.
Often an earlier maturing variety will have fewer problems than a later one, as towards the end of the season there will have been more opportunity for pest populations to become established. Some tropical fruits have natural defences against pests, like a thick layer of latex in jackfruit or bitter or toxic skin like star apple. I’m a lazy gardener; I figure if it doesn’t grow well, find something else that does.
If you really must grow something that has problems (perhaps you know that it gets a good price or maybe you just want to grow it), you might have to move to the next stage:
2) Timely Intervention
Timing once again is crucial. Weeds are an obvious example. The best time to interrupt weeds lifecycle is before it starts. If you have disturbed or bare ground it will soon fill up with weeds if you don’t fill it up with something else. Even if you are not ready to plant a crop somewhere, you can plant the disturbed soil with green manure crops such as lab lab or mung bean, which will cover the soil and smother or prevent new weeds from taking control. Other good weed and grass suppressors include sweet potato and strong vines such as pumpkins. For large areas of new earthworks, bags of birdseed also do the job, especially if it’s for revegetation, as the birds that are attracted to the resulting crop will bring wild tree seeds as well as phosphates to the site. If you do have an area with weeds it’s important not to let them set seed: ‘One years seeding means seven years weeding’ as the old saying goes. Weeds are a pest because they spread themselves so readily, usually by abundant seeds. Let them set seed and you’ll be dealing with hundreds more of their offspring next season (or in some cases the next seven seasons). Almost any weed can be used for mulch if you get it before it seeds. All weeds are easier to pull out when they’re small, but let them get their big taproots down and you’ll leave half of it there to regrow.
Insects are similar, under suitable conditions their populations grow exponentially. You can deal with a small number of white flies or fruit flies with sticky traps, but they probably won’t work once a population becomes established. The other good thing about traps is that they are an excellent way to monitor pests and indicate when control measures are needed and whether or not those methods are working. Observation is a crucial strategy.
Another important thing is to learn about the lifecycles and ecology of pests and use that knowledge against them. A good example in temperate regions relates to fruit flies. Depending on the temperature and species, the life cycle of fruit flies takes up to several weeks. In temperate areas over winter there is no fruit available for the fruit flies and so a fresh infestation has to occur each spring. If loquats are present, they fruit over the winter months, providing a food source which ensures a ready supply of adult flies to infest the next crop. So we can see that in some regions removing สoquats and any other source of overwintering habitat can greatly reduce the severity of fruit flies. ‘Break’ crops and crop rotation work in the same way.
3) Remedial action
One of the first things to take into account is whether or not remedial action is warranted. Some pests, such as minor infestations of scales or thrips on the skin of citrus fruits only cause cosmetic damage and do not affect the quality of the product. This may be an issue for commercial growers, but even then one has to take into account whether the cost of control will be greater than the potential economic loss (blemished or damaged fruit can often be used for juice, jams or preserves). In many cases damage is done while fruit is forming, and the pest is long gone by the time it is noticed. Once again, observation is a crucial strategy.
Many more strategies are available to the home gardener or small mixed farmer than the industrial monoculturist. Often mechanical or physical control will be the simplest and least harmful method. If you only have a couple of dozen tree seedlings or a small bed of cabbages, why would you need to mix up a caterpillar spray when you can just pick them off by hand? Things like aphids or mealy bugs can often be discouraged with a vigorous hosing down (a garden hose is like a water cannon when you are only a couple of millimetres in size). Heavy pruning can also control many pests and some diseases of perennials; they are concentrated on the new growth and depend on it to survive. The week or so it takes for your plant to produce new growth can be enough to wipe out the population.
Various traps can be devised, like the sticky traps mentioned before, or funnel traps for flying insects. You are limited only by your imagination and your knowledge of the target pest. I can’t vouch for the drinking habits of Thai snails and slugs, but a great way to control snails in Australia is with beer traps; a saucer of beer is placed out in the garden and they are so attracted to it they become inebriated and end up drowning in it (I think that’s more humane than a lot of other methods!) Nature has devised all sorts of insect traps and a study of carnivorous plants can provide great inspiration; there are sticky traps, pitfall traps, funnel traps and all types of variations and combinations. Carnivorous plants themselves can be used for pest control. I have used tropical pitcher plants (Nepenthes) with great results for pest control in glasshouses.
Even better are traps designed so that the pest automatically becomes food for something else like fish or chickens; flying insect traps over fish ponds, or even just a light over a fish pond, turn a pest into a resource.
Other areas worthy of study are companion plants. Some repel or confuse insects with their odour or chemical compounds; marigolds are a well known plant used to discourage nematodes; citronella and rose-scented geranium for mosquito are others. Trap or decoy crops, where a specific pest has a preference for something over the target crop can also be very effective. Once again, observation is critical because every situation is different.
4) Exclusion strategies
Sometimes the only viable option is to isolate certain crops and exclude pests. In areas with large populations of wildlife, cages over whole gardens or bird nets over individual trees can be the only way to get a crop through. For high value organic crops, sometimes cages with insect screen are used to completely exclude insects. This may not be as unviable as it sounds, when you consider the expense of time and money and crop losses that is regularly spent on pest control. Once again, the home gardener or small mixed farmer has much more scope to use these strategies. On a small scale, individual fruits can be protected with waxed paper bags or even wrapped in newspaper to protect them from insect attack. Plastic banana bags not only enhance the ripening of banana bunches, but also protect them from birds. The old scarecrows can be helpful as well, and there are many variations on the theme, including suspended hawk kites over a crop. The crucial thing here is that the scarers are not left out all the time, as birds will become accustomed to them.
5) Sprays; the last resort
If all of the above doesn’t work, and you must spray, there are a whole range of pest controls which are less toxic than agrochemicals, and we should always go for the least toxic option. Be aware that just about any poison you use will also kill your beneficials, so you need to assess whether or not it’s really worthwhile and necessary. The options available are too numerous to be covered in this article, but include preparations of naturally occurring pathogens such as Bt (a fungus which attacks caterpillar digestive systems), insecticidal soaps and oils, and naturally occurring poisons such as pyrethrum, neem and rotenone. It must be remembered though, that just because a compound is natural, it doesn’t make it safe; uranium and cyanide are perfectly natural too!
Good on ya cob and co…..