I grow about 200 pounds of carrots a year(Bolero) and I adhere faithfully to crop rotation but my carrot fly problem seems to be getting worse. The majority of the carrots have worms that keep on eating the carrots in cold storage. Any idea on countering this problem.
Look what I found, I wasn't sure if I could just give the address so I cut and pasted the whole thing!
How to Manage Pests UC Pest Management Guidelines | More pests | More crops | About guidelines |
CARROT WHITEFLIES Scientific Names: Greenhouse whitefly: Trialeurodes vaporariorum Iris whitefly: Aleyrodes spiraeoides Sweetpotato whitefly: Bemisia tabaci Silverleaf whitefly: Bemisia argentifolii (Reviewed: 7/01, updated: 7/01) IN THIS GUIDELINE: DESCRIPTION OF THE PESTS DAMAGE BIOLOGICAL CONTROL CULTURAL CONTROL ORGANICALLY ACCEPTABLE METHODS MONITORING AND MANAGEMENT DECISIONS PUBLICATION GLOSSARY
DESCRIPTION OF THE PESTS Whiteflies are small insects that are about 0.04 inch (1 mm) long. The body and wings of adults are covered with a fine, whitish powdery wax that is opaque in appearance. Whiteflies colonize the underside of leaves; adults and eggs are commonly found on the lower surface of younger leaves and the scalelike nymphal stages on somewhat older leaves. Distinguishing whitefly species is difficult; use a hand lens to examine both immatures and adults. Adult silverleaf whiteflies hold their wings somewhat vertically tilted like the peaked roof of a house, instead of flat over their bodies like the greenhouse whitefly. During the last part of the fourth larval stage, often called the pupa, the whitefly develops red eyes and stops feeding. This is the stage that is easiest to identify silverleaf whitefly; pupae have no waxy filaments around their edges as do most other species of whiteflies.
DAMAGE Extremely dense populations of silverleaf whitefly may immigrate into late August or September plantings of carrots in the low deserts of southern California and damage seedlings. In light to moderate infestations, leaves show no distinctive symptoms as a result of whitefly feeding; however, copious quantities of honeydew are deposited on leaves, resulting in a shiny, sticky appearance.
BIOLOGICAL CONTROL Several parasitic wasps, including species in the Encarsia and Eretmocerus genera, control whiteflies. Whitefly nymphs are also preyed upon by bigeyed bugs, lacewing larvae, and lady beetles. The lady beetles, Delphastus pusillus and Serangium parcesetosum, are being introduced into southern California to assist in biological control. Encourage buildup of beneficial insects by avoiding the use of nonselective pesticides and by protecting their habitat.
CULTURAL CONTROL Remove field bindweed and other weeds in and adjacent to the crop field as well as crop residues. Host free periods are valuable for controlling several of the whitefly species. Contact your Cooperative Extension Office for a list of hosts that harbor the silverleaf whitefly.
ORGANICALLY ACCEPTABLE METHODS Biological and cultural controls, as well as soap sprays.
MONITORING AND MANAGEMENT DECISIONS Carrots are not a preferred host of whiteflies and treatment with insecticides is rarely justified. However, when dense populations of adult silverleaf whitefly are migrating, monitor seedling carrot fields at least twice weekly and treat if necessary. Occasionally dense colonies of silverleaf whitefly nymphs can necessitate treatment of bunching carrots to prevent honeydew and sooty molds from severely contaminating the carrot tops.
Whiteflies can be very difficult or almost impossible to control with insecticides. Natural or introduced biological methods provide the best long-term solution to keeping whitefly numbers at a minimum along with reducing host plants in areas of heavy infestation. If you treat for silverleaf whitefly, make applications before pests build up and contaminate carrot tops with honeydew. Combinations of a pyrethroid insecticide (esfenvalerate) with either methomyl or endosulfan provide superior control over applications of a single insecticide. Rotate pyrethroid treatments with a treatment of insecticidal soap to help slow development of insecticide resistance. There is some evidence of endosulfan resistance in populations of silverleaf whitefly in the Imperial Valley. Insecticidal soaps control all immature stages of whiteflies, including eggs, whereas the other materials control first instar nymphs and adults only; thus, treatment timing is critical. Emergency registrations may be in effect in some areas for new materials. Check with your local county agricultural commissioner.
I use row covers. I put them flat on the ground after seeding than as they seeds germinate the covers go on wire hoops. I remove the covers for weeding but put them back on ASAP. I have almost no carrot fly maggot damage since doing this.
