Management Western corn rootworm

1 management

1.1 variety
1.2 planting
1.3 insecticides
1.4 crop rotation
1.5 natural enemies
1.6 transgenics

management

multiple management practices aim control corn rootworms. these practices include corn variety selection, planting, insecticides, crop rotation , transgenic corn varieties.

variety

no commercial, non-transgenic resistant corn varieties available. several hybrid corn traits reduce damage increasing stalk strength , root mass size. these characteristics allow plant better tolerate rootworm feeding, reduced likelihood of lodging.

early planting

early planted fields have completed pollen shed less attractive , therefore have less egg laying activity. fields have relatively larger root systems when rootworm feeding starts. makes them more tolerant. practices promote strong root systems , vigorous crop make corn more tolerant rootworm feeding , damage.

insecticides

soil-applied insecticides control corn rootworms. insecticide may warranted in areas have history of moderate high damage. number of adults present during previous growing season best guide selecting fields treated. however, in areas of high insecticide use in central nebraska, populations of corn rootworm beetles have become resistant insecticides. aldrin resistance introduced independently, @ least twice, north america europe. organophosphates, such methyl-parathion, may provide effective control of both larval , adult populations in central , southeastern europe , in northwest italy.

crop rotation

crop rotation consistent , economical means of controlling rootworms season following outbreak in corn-growing areas rootworm beetles lay eggs in corn. way reduce rootworm densities, more effective insecticides. corn rootworm larvae must feed on corn roots develop , mature properly. if hatch in field without corn, starve because cannot move more 10 20 inches (510 mm) in search of food. however, 2 rootworm biotypes survive rotation. soybean variant first discovered in central illinois in late 1980s , spread throughout illinois, indiana, southern wisconsin , eastern iowa. instead of laying eggs corn field, females of soybean variant mate , fly soybean field lay eggs, allowing larvae hatch in field rotate corn following year. in 1980s northern corn rootworm began problem beating corn rotation practice extended diapause eggs. eggs remained in soil 2 years or more before hatching, thereby avoiding soybean year. adaptation has been observed in areas of northern iowa, minnesota , south dakota.

companion or second crop planting can dramatically increase rootworm populations. corn pumpkins or corn following pumpkins examples of planting patterns exacerbate rootworm feeding pressure.

natural enemies

among natural enemies - argiope bruennichi, theridion impressum, coccinella sp., pseudophomus rufipes.

transgenics

planting rootworm-resistant transgenic corn, strategy minimizing damage. bt corn effective @ reducing root damage , safer , cheaper insecticide. transgenic traits, isolated common soil bacterium bacillus thuringiensis strain (often referred bt), produce insect control protein.

bt first discovered in 1901 japanese biologist s. ishiwatari source of disease killing large populations of silkworms. bt first used insecticide in 1920 , spray formulations containing either bt bacteria or bt proteins came use in 1970s crop protection, including organic farming operations. bt insecticides saw expanded use , development in 1980s alternative synthetic insecticides. beginning in 1980s, genes responsible making bt proteins isolated , transferred corn plants. bt commercially approved in transgenic corn seed in mid-1990s. compared spray formulations, transgenic plants bt protein provide more effective insect protection throughout season. other bt proteins have been used genetically modify potatoes, cotton , other types of commercial corn. 2 common brands of transgenic bt corn genuity , herculex. genuity smartstax combines monsanto s vt triple pro, roundup ready 2, , acceleron seed treatment system technologies, dow chemical s herculex xtra , liberty link technologies. acceleron, herculex xtra, , vt triple pro include traits protection insect damage.

bt must ingested kill insect. susceptible larva eats protein, binds receptors in larval gut. binding initiates cascade of effects leads death. bt proteins highly selective on categories , species of insects, eliminating insecticide use , harmful effects non-target organisms.

recently, however, strains of rootworms have been discovered in several midwest states exhibit bt resistance. according monsanto, “yieldgard® vt triple , genuity® vt triple pro™ corn products” affected. in 2009, 4 strains in iowa found have field-evolved resistance bt corn.

by 2014 syngenta agrisure rw-rootworm strains had been detected in iowa glyphosate. agrisure rw-based products entered market in 2007. however, government officials, academics , companies lack consensus on how define resistance phenomenon. affected fields constituted 0.2% of transgenic corn acres. further affected areas had not been rotated other crops.

as of 2014 herculex , agrisure duracade had not produced resistant outbreaks.