Trap crop
Encyclopedia
A trap crop is a plant that attracts agricultural pests, usually insects, away from nearby crops. This form of companion planting
can save the main crop from decimation by pests without the potential issues and controversy involved in using pesticides.
Trap crops can be planted around the circumference of the field to be protected, or interspersed among them, for example being planted every ninth row.
Examples of trap crops include:
The host-plant finding process occurs in three phases.
The first phase is stimulation by odours characteristic to the host-plant. This induces the insect to try to land on the plant it seeks. But insects avoid landing on brown (bare) soil. So if only the host-plant is present, the insects will quasi systematically find it by simply landing on the only green thing around. This is called an “appropriate landing”. When it does an “inappropriate landing”, it flies off to any other nearby patch of green. It eventually leaves the area if there are too many ‘inappropriate’ landings.
The second phase of host-plant finding is for the insect to make short flights from leaf to leaf to assess the plant's overall suitability. The number of leaf-to-leaf flights varies according to the insect species and to the host-plant stimulus received from each leaf. But the insect must accumulate sufficient stimuli from the host-plant to lay eggs; so it must make a certain number of consecutive ‘appropriate’ landings. Hence if it makes an ‘inappropriate landing’, the assessment of that plant is negative and the insect must start the process anew.
Thus it was shown that Clover
used as a ground cover had the same disruptive effect on eight pest species from four different insect orders. An experiment showed that 36% of cabbage root flies laid eggs beside cabbages growing in bare soil (which resulted in no crop), compared to only 7% beside cabbages growing in clover (which allowed a good crop). Also that simple decoys made of greencard disrupted appropriate landings just as well as did the live ground cover.
Companion planting
Companion planting is the planting of different crops in proximity , on the theory that they assist each other in nutrient uptake, pest control, pollination, and other factors necessary to increasing crop productivity...
can save the main crop from decimation by pests without the potential issues and controversy involved in using pesticides.
Trap crops can be planted around the circumference of the field to be protected, or interspersed among them, for example being planted every ninth row.
Usage
Trap crops are, when used on an industrial scale, generally planted at a key time in the pest's lifecycle, and then destroyed before that lifecycle finishes and the pest might have transferred from the trap plants to the main crop.Examples of trap crops include:
- AlfalfaAlfalfaAlfalfa is a flowering plant in the pea family Fabaceae cultivated as an important forage crop in the US, Canada, Argentina, France, Australia, the Middle East, South Africa, and many other countries. It is known as lucerne in the UK, France, Australia, South Africa and New Zealand, and known as...
planted in strips among cottonCottonCotton is a soft, fluffy staple fiber that grows in a boll, or protective capsule, around the seeds of cotton plants of the genus Gossypium. The fiber is almost pure cellulose. The botanical purpose of cotton fiber is to aid in seed dispersal....
, to draw away lygusLygusThe genus Lygus includes over 40 species of plant-feeding insects in the family Miridae. At one time, nearly 200 species were classified as genus Lygus, but most of those have since been reclassified into new or existing genera. The term lygus bug is used for any member of genus Lygus. The more...
bugs, while castor beanCastor oil plantThe castor oil plant, Ricinus communis, is a species of flowering plant in the spurge family, Euphorbiaceae. It belongs to a monotypic genus, Ricinus, and subtribe, Ricininae. The evolution of castor and its relation to other species are currently being studied.Its seed is the castor bean which,...
s surround the field, or tobaccoTobaccoTobacco is an agricultural product processed from the leaves of plants in the genus Nicotiana. It can be consumed, used as a pesticide and, in the form of nicotine tartrate, used in some medicines...
is planted in strips among it, to protect from the budworm HeliothisHeliothisHeliothis is a genus of moths, whose larvae are agricultural pests on crop species such as tobacco, cotton, soybean and pigeon pea. Several of the species formerly placed in this genus are now in the genus Helicoverpa.-Species:...
. - RoseRoseA rose is a woody perennial of the genus Rosa, within the family Rosaceae. There are over 100 species. They form a group of erect shrubs, and climbing or trailing plants, with stems that are often armed with sharp prickles. Flowers are large and showy, in colours ranging from white through yellows...
enthusiasts often plant PelargoniumPelargoniumPelargonium is a genus of flowering plants which includes about 200 species of perennials, succulents, and shrubs, commonly known as scented geraniums or storksbills. Confusingly, Geranium is the correct botanical name of a separate genus of related plants often called Cranesbills. Both Geranium...
geraniums among their rosebushes because japanese beetleJapanese beetleThe beetle species Popillia japonica is commonly known as the Japanese beetle. It is about long and wide, with iridescent copper-colored elytra and green thorax and head...
s are drawn to the geraniums, which are toxic to them. - ChervilChervilChervil is a delicate annual herb related to parsley. Sometimes called garden chervil, it is used to season mild-flavoured dishes and is a constituent of the French herb mixture fines herbes.-Biology:...
is used by gardeners to protect vegetable plants from slugSlugSlug is a common name that is normally applied to any gastropod mollusc that lacks a shell, has a very reduced shell, or has a small internal shell...
s. - RyeRyeRye is a grass grown extensively as a grain and as a forage crop. It is a member of the wheat tribe and is closely related to barley and wheat. Rye grain is used for flour, rye bread, rye beer, some whiskeys, some vodkas, and animal fodder...
, sesbaniaSesbaniaSesbania is a genus of flowering plants in the pea family, Fabaceae and the only genus found in Tribe Sesbanieae. Notable species include the Rattlebox , Spiny Sesbania , and Sesbania sesban, which is used in cooking...
, and sicklepodSenna obtusifoliaSenna obtusifolia is a legume in the genus Senna, sometimes separated in the monotypic genus Diallobus. It grows wild in North, Central, and South America, Asia, Africa, and Oceania, and is considered a particularly serious weed in many places...
are used to protect soybeans from corn seeding maggotDelia (genus)The genus Delia is part of the fly family Anthomyiidae.The genus Delia contains approximately 300–340 species worldwide . At present about 170 species are recorded from the Palaearctic Region, and 162 species from the Nearctic Region, 44 of which are Holarctic. Afrotropical fauna includes 20 Delia...
s, stink bugs, and velvet green caterpillarCaterpillarCaterpillars are the larval form of members of the order Lepidoptera . They are mostly herbivorous in food habit, although some species are insectivorous. Caterpillars are voracious feeders and many of them are considered to be pests in agriculture...
s, respectively. - MustardMustard plantMustards are several plant species in the genera Brassica and Sinapis whose small mustard seeds are used as a spice and, by grinding and mixing them with water, vinegar or other liquids, are turned into the condiment known as mustard or prepared mustard...
and AlfalfaAlfalfaAlfalfa is a flowering plant in the pea family Fabaceae cultivated as an important forage crop in the US, Canada, Argentina, France, Australia, the Middle East, South Africa, and many other countries. It is known as lucerne in the UK, France, Australia, South Africa and New Zealand, and known as...
planted near strawberriesStrawberryFragaria is a genus of flowering plants in the rose family, Rosaceae, commonly known as strawberries for their edible fruits. Although it is commonly thought that strawberries get their name from straw being used as a mulch in cultivating the plants, the etymology of the word is uncertain. There...
to attract lygus bugs, a method pioneered by Jim CochranJim CochranJim Cochran is a pioneering organic strawberry farmer, who was the first person to grow strawberries organically on a commercial scale in California. Cochran was born in Carlsbad, California in 1947. He studied child development and European intellectual history at the University of California,...
.
Operation
Recent studies on host-plant finding have shown that flying pests are far less successful if their host-plants are surrounded by any other plant, or even “decoy-plants” made of green plastic, cardboard or any other green material.The host-plant finding process occurs in three phases.
The first phase is stimulation by odours characteristic to the host-plant. This induces the insect to try to land on the plant it seeks. But insects avoid landing on brown (bare) soil. So if only the host-plant is present, the insects will quasi systematically find it by simply landing on the only green thing around. This is called an “appropriate landing”. When it does an “inappropriate landing”, it flies off to any other nearby patch of green. It eventually leaves the area if there are too many ‘inappropriate’ landings.
The second phase of host-plant finding is for the insect to make short flights from leaf to leaf to assess the plant's overall suitability. The number of leaf-to-leaf flights varies according to the insect species and to the host-plant stimulus received from each leaf. But the insect must accumulate sufficient stimuli from the host-plant to lay eggs; so it must make a certain number of consecutive ‘appropriate’ landings. Hence if it makes an ‘inappropriate landing’, the assessment of that plant is negative and the insect must start the process anew.
Thus it was shown that Clover
Clover
Clover , or trefoil, is a genus of about 300 species of plants in the leguminous pea family Fabaceae. The genus has a cosmopolitan distribution; the highest diversity is found in the temperate Northern Hemisphere, but many species also occur in South America and Africa, including at high altitudes...
used as a ground cover had the same disruptive effect on eight pest species from four different insect orders. An experiment showed that 36% of cabbage root flies laid eggs beside cabbages growing in bare soil (which resulted in no crop), compared to only 7% beside cabbages growing in clover (which allowed a good crop). Also that simple decoys made of greencard disrupted appropriate landings just as well as did the live ground cover.