5 minute read
Les Davies MBEOutdoors
Beat the bugs with biological control
Afterthe cold nights in April, and April showers in May, hopefully we can get back into our gardening routines. the bedding plants and runner beans are planted out and growing away, herbaceous plants are staked before they even think With MARY PAYNE MBE about flopping, and the tomato flowers are setting well in the greenhouse. So, we can now turn our attention to dealing with all the variety of little critters that wish to destroy our best efforts and eat our crops before we do. As less and less effective sprays, quite rightly, are available to us, we need to move into the world of biological control in our gardens. traps for the horse chestnut leaf miner that causes so much the horticultural industry has been there for many years unsightly damage to the foliage and box tree caterpillar. the and we are now able to benefit from their research into who latter is likely to be heading your way between April and controls what and how to go about it. there are basically October. this moth lays hundreds of eggs which can hatch three approaches. trap it, eat it, or lay eggs in it. into voracious caterpillars and can easily defoliate a box bush. the “trap it” approach has been around for many years in Once you have an infestation, then a different approach is the form of grease or glue bands applied to the trunks of fruit required – read on. even the dreaded chafer grubs that cause trees to control winter moth. the female winter moth is havoc in lawns and borders can be caught by an appropriate wingless so after emerging from a chrysalis that has trap. One trap will not catch all the aforementioned pests, you overwintered in the soil, she must climb up the trunk to lay will need a separate trap for each species. her eggs on the flower clusters. In greenhouses we can employ a different “eat it” approach
On the way up she gets stuck to the grease so cannot mate and release “good” bugs to control the “bad” bugs either by with the winged male moths flying above waiting for her. gobbling them up or by parasitising them. A common Grease bands have no effect on codling moth numbers as both greenhouse pest on cucumber, melon and almost any plant is the the male and female can fly. tiny two spotted spider mite. this pest sucks the sap of the plants
Yellow sticky traps have been hung in greenhouses to trap leaving a mottled appearance and weakening the plant. anything that likes yellow especially the pesky glasshouse Another “good” tiny spider, (Phytoseilus persimmilis) runs whitefly that likes tomatoes and plenty more. thrips prefer around eating all the “bad” spider mites without harming blue so blue sticky traps are used to monitor the level of anything else. Check the temperature that these “good” bugs particularly western flower thrips which can devastate prefer and ensure you have a population of tasty pests for glasshouse crops. them to eat before introducing them.
We have now moved on from basic glue traps to specific Both the adult and larval stage of ladybirds and lacewings pheromone traps. these use the sex hormone of the female of are excellent at dining on greenfly in the garden, likewise, a single species to lure the male to his death, again on a earwigs and the larvae of the hoverfly. sticky platform. In commercial horticulture these are used to the glasshouse whitefly, the scourge of tomato plants, can be give an indication of the level of pest infestation and are controlled by the “lay eggs in it” approach by the introduction of unlikely to give complete control. a minute wasp, Encarsia formosa, which lays its eggs in the
In our gardens they are useful tool to reduce populations to immobile nymph stage of the whitefly, turning them black. New a tolerable level. the great advantage of these pheromone parasitic wasps emerge to continue the good work. traps is that they only catch the intended prey as only they are Microscopic eelworms can be deployed to control slugs, attracted by the scent, leaving all other insects to go about vine weevil grubs and chafer grubs. the eelworm transmits a their business unharmed. deadly bacterium to the grubs, rather than devouring them. the most popular of this type has been the pheromone trap read the instructions very carefully as some of these for codling moth. this is the remains of the grub you often eelworms are sensitive to low temperatures (aren’t we all!) get inside an apple after taking a bite! the trap should be and the soil must be always kept moist to enable them to hung in the tree between May and August and one trap will swim around and find the slugs or grubs. Lack of adequate protect about five trees. soil moisture is the most common reason for failure with
A similar product is available to help control the grub these products. inside plum fruits, aka plum moth and should be used at a Bacteria are also used in the control of box caterpillar. similar time to the codling moth trap. Similar traps are Bacillus thuringensis in conjunction with a plant feed can be available for pea moth (the grub inside peas) and raspberry sprayed onto affected plants. Care must be taken not to use moth grub. this product on other plants as the bacteria can attack any
Leek moth has in recent years had a devastating effect on caterpillars. leeks on allotments but can now be controlled in a similar Using good bugs to defeat the bad bugs is the future of pest way between May and June and again from August to October control both for the amateur and professional. remember that when the second generation of adults are on the wing. these are live creatures you are introducing, so take care of two promising introductions in this field are pheromone them on arrival.
