Carrot fly

On a field scale, it has been shown that carrots grown with onions are less damaged by carrot fly as long as there are four times as many onions as carrots, but that the effect only lasts while the onions are actively growing, and stops once they start to produce bulbs. This may not be as effective on a garden scale. 

What to do Grow in a well-drained site. Grow a resistant variety such as Avonresister. Earth up in summer to stop the spores of black canker from reaching the roots. Use close spacing to produce smaller roots that may be less susceptible to some cankers. Control carrot fly (q.v.). Use a crop rotation. 

The antennal olfactory receptor system in several phytophagous insects is very sensitive in the detection of the green odour components. In the Colorado beetle Leptinotarsa decemlineata, the threshold of response for trans-2-hexen-1-ol is circa 10b molecules per ml of air (17). In comparison, at 760 mm Hg and 20 C, 1 ml of air contains about 1019 molecules. The insects tested i.e., the migratory locust Locusta migratoria, the carrot fly Psila rosae (18), the cereal aphid Sitobion avenae (19), the Colorado beetle L. decemlineata (17), Leptinotarsa... 

The catches of carrot flies in yellow sticky traps are enhanced by the release of hexanal and compounds isolated from the surface wax of carrot leaves i.e., trans-methyliso-eugenol and trans-asarone (28,29). The propenylbenzenes also stimulate oviposition by this insect (29). 

Escape Shorter crop growth period and/or early ripening to be able to avoid the critical infestation period, or to have enough yield before the infestation becomes too severe (potato/late blight onion/downy mildew carrot/carrot fly) One or more monofactorial and multifactorial, durable resistance traits against pest and disease affecting yield and/or quality (scab/apple, late blight/potato, lettuce/downy mildew, yellow and brown leaf rust/wheat) weed competition by an allelochemical ability... 

Blackfly Carrot fly Flea beetles Greenfly Leafhoppers Thrips Whitefly Wireworms... 

Interplanted with carrots, it may help to reduce carrot fly and thrips. 

Can confuse pests such as leafhoppers, aphids, and carrot fly. 

Farcarindiol is a constitutive metabolite of Daucus carota (carrot) and is the main component of the mixture of six compounds in the leaf wax that attracts and induces egg-laying by the carrot fly. The compounds all occur in leaves of other Umbellifereae, but the particular profile of components is characteristic of carrot and acts as a marker for the insect. In contrast, other alkynes act as anti-feeding agents for certain Pieris (cabbage) butterflies. ... 

Diazinon, an organophosphoras compound with an anticholinesterase mode of action, was released for experimental evaluation in the early 1950s. Diazinon is now used extensively hy commercial and home applicators in a variety of formulations to control flies, cockroaches, lice on sheep, insect pests of ornamental plants and food crops (especially com, rice, onions, and sweet potatoes), forage crops such as alfalfa, and nematodes and soil insects in turf, lawns, and croplands. Diazinon is the most widely used organophosphorus pesticide in Pakistan to control cabbage root fly and carrot fly. In 1992, more than 612,000 kg of diazinon were used in California on alfalfa, nuts, stone fmits, vegetables, and other crops. 

Guerin, P. M., E. Stadler, and H. R. Buser, Identification of host plant attractants for the carrot fly, Psila rosae, J. Chem. Ecol., 9, 843-861 (1983). 

A mixture of volatiles from carrot Daucus carota, Apiaceae) is responsible for oviposition by females of the carrot fly Psila rosae). Among these are the phenylpropanoids. E-methyleugenol, -asarone, a prenylated coumarin, osthol (31), bergapten (18), xanthotoxin (19), and an acetylenic compound, falcarindiol (Harbome, 1986). No single component of the mixture is responsible for the behavior of the fly. 

Jones, O. T. and Coaker, T. H. (1979) Responses of carrot fly larvae, Psila rosae, to the ordorous and contact-chemostimulatory metabolites of host and non-host plants. Physiol. Ent., 4, 353-60. 

Turning to examples where the group Y is a heterocyclic system as we have already seen earlier in this chapter, and also in the pharmaceutical field (Chapter 4), the pyrimidine and triazine ring systems are prominent in many biologically-active molecules and the same is true in the organophosphate field. Diazinon, introduced by Geigy in 1951, is a non-systemic insecticide with fairly low mammalian toxicity, good residual activity and a wide spectrum of activity, e.g. aphids, carrot flies, spider mites. 

Fleece or net crop covers will stop egg laying of some pests such as carrot fly. On a field scale it is expensive although a very effective optiom hr swedes this is the only method available to growers to control cabbage root fly as there are cmrently no suitable recommended chemicals. 

Economic thresholds have been calculated for many pests and are an important tool in IPM. An eeonomie threshold is the population of pests which if controlled will give a yield return that will pay for the cost of pesticide and application. Where available these have been ineluded in Table 7.1. Another important tool to help with deeision making for appheation of a pesticide is the use of forecasts of pest populations. A number of oiganisations run forecasting services for some important crop pests sueh as eutworm, pea moth and carrot fly. These forecasts combined with erop monitoring and use of traps including pheromone traps can all help to reduee the requirement for pestieide applications. 

Time of sowing can be very important for reducing pest problerrrs. Cereal growers in high-risk areas normally drill winter cereals after the rrtiddle of October to reduce aphid attack arrd trarrsfer of barley yellow dwarf virus (BYDV). MairKrop carrots are sown at the end of May or in early Jrme to avoid the first generation of carrot fly. 

Carrot fly, cutworms, willow-carrot aphids and nematodes, and the diseases violet root roL black rot, leaf bhght, cavity spof scab and Sclerotinia rot are the main problems in the growing of the crop. Some varieties are more susceptible to cavity spot than others. 

More detailed information on turning rates and movements can be obtained by providing a surface on the petri dish that will record and retain the larval tracks. Jones and Coaker (1977) utilized a thin layer of agar coated with talc over which larvae of the carrot fly, Psila rosae, crawled. Larval tracks were evident in the talc field, and permanent records of larval movement were made by photographing the plates. Time-lapse photography also has been used to provide a permanent track of movement in relatively small arenas (Bell Tobin 1981), and more modem video equipment provides greater flexibility for such recording. 

Jones, O.T. T.H. Coaker. 1977. Oriented responses of carrot fly larvae, Psila rosae, to plant odours, carbon dioxide and carrot root volatiles. Physiol. Entomol. 2 189-197. 

Degen, T., Buser, H.-R. and Stadler, E. (1999) Patterns of oviposition stimulants for carrot fly in leaves of various host plant. /. Chem. Ecol., 25, 51-%1. 

Cole, R.A. (1985) Relationship between the concentration of chlorogenic acid in carrot root and the incidence of carrot fly larval damage. Ann. Appl. Biol, 106, 211-217. 

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