Insecticides Required to Meet Consumer Demands for Blemish-Free Carrots in the EU

nasty carrots

Carrot Fly Damage

Carrot is one of the most important vegetable crops in the EU with 6 billion pounds of annual production. The carrot fly is the major insect pest of the carrot crop in Europe. Before the introduction of insecticides in the 1950s, the carrot fly typically damaged 20-50% of the carrots grown in Europe. In some parts of Europe, the damage from the carrot fly was so severe that it was not profitable to grow carrots. Today, European carrot growers spray insecticides to prevent damage from the carrot fly.

“Carrot fly, is the most widespread and serious pest of carrot, parsnip, parsley and certain other umbelliferous herbs in temperate regions of the world. … The insect has two and, in some parts of Britain, Europe and New Zealand, three generations each year. Adult insects feed on the nectar and pollen provided by flowers and spend most of their life in the hedgerows, ditches or amongst herbaceous plants in gardens. Females search out carrot plants to lay their eggs which are inserted in crevices around the crown of the host plant. The larvae, which emerge from the eggs, migrate downwards to feed on plant roots.

Carrots grown commercially can be rendered unmarketable by even slight carrot fly damage.

To meet the stringent levels of blemish-free produce demanded by the supermarkets in the UK and Europe, commercial carrot production depends precariously on a few insecticides to control this pest.”

Author: Ellis, P. R.
Affiliation: Horticulture Research International, UK.
Title: The identification and exploitation of resistance in carrots and wild Umbelliferae to the carrot fly, Psila rosae (F.)
Source: Integrated Pest Management Reviews. 1999. 4:259-268.

Organic Vegetable Crops Require Thousands of Hours of Weeding by Hand

The biggest constraint to the expansion of organic crop growing is the lack of chemical controls for weeds – herbicides. Hand weeding is often required to remove weeds from organic fields. A very large number of worker hours are required for weeding, as reported in a recent article from Germany…

“In organic crop production, manual control of weeds is still laborious in a number of row crops that have poor competitive ability. It is difficult to control weeds that grow within the crop rows (intra-row weeds) by physical weed control; typical figures for hand-weeding time are in the range of 100-400 hours/hectare in carrot, direct-sown leek and onion, and it has even been reported to exceed 1000 hours/hectare.” 

Authors: J Rasmussen¹, C B Henriksen¹, H W Griepentrog² and J Nielsen¹
Affiliations: ¹University of Copenhagen, Denmark; ²University of Hohenheim, Germany
Title: Punch planting, flame weeding and delayed sowing to reduce intra-row weeds in row crops.
Publication: Weed Research. 2011. 51:489-498.

Cancellation of Effective Insecticides Puts Carrots at Risk of Rejection by Food Companies

The carrot weevil is native to northeastern North America. Each female can lay 300 eggs. After hatching and entering the carrot, the larvae tunnel through the carrot, filling the tunnels with excreta. The epidermal cells around the tunnels die and become dark brown. The presence of larvae, excreta and feeding damage are of major concern to carrot processors because of strict FDA quality control in processed foods. Processors are unwilling to accept carrots if they find one live larva in a sample or if the carrots have more than 1% damage. Since the 1940s, effective broad spectrum insecticides kept carrot weevil damage to a minimum; however, the most effective insecticides have been cancelled for use in the US.

“Adults [carrot weevils] overwinter in and near carrot fields where carrots were grown the previous year, emerging in late April to early May in New Jersey. The adults feed directly on the leaves and crowns of carrots, and females oviposit from the beginning of May until late June in carrot roots. Larvae tunnel extensively throughout the upper third of the roots, damaging 80% or more of the carrots in untreated processing carrot fields.”

“Consequently, pesticide applications are directed at adult weevils to prevent or reduce oviposition. … However, during the past several years, carrot weevil damage has been increasing in New Jersey carrot farms, and the damage has been as high as 90% loss on farms in Salem County. These losses are partly due to the cancellation of broad-spectrum insecticides, such as parathion, azinphos-methyl, and phosmet during the early 1990s.”

Authors: G.M. Ghidiu¹, E. Hitchner², M. Zimmerman¹ and E. Rossell¹
Affiliations: ¹Rutgers University; ²Virginia Tech
Title: Effect of two different nozzle arrangements on control of carrot weevil, Listronotus oregonensis (LeConte), in processing carrots.
Publication: Plant Health Progress. April 3, 2006.

Fungicides Essential to Carrot Production Worldwide

Organisms that cause diseases on carrot foliage are present wherever carrots are grown. Research has demonstrated that using fungicides to control these foliar pathogens increases carrot yields by 4-8 tons/acre.

“Alternaria leaf blight (ALB) of carrot and cercospora leaf spot (CLS) contribute to significant and recurrent losses for the production of carrots worldwide. … Foliar pathogens defoliate carrots by infecting and blighting leaflets and petioles, which in turn limits photosynthesis and energy storage in roots. Several field studies have shown 20%-80% yield loss for unsprayed carrots compared with carrots subjected to a standard calendar fungicide program.”

“In addition to yield loss, deterioration of petiole and leaf health may reduce the commercial harvestability of roots since strong, healthy petioles are required to properly lift and remove carrots from the soil. When foliage is weakened by disease, additional crop losses ensue as unharvested roots are left behind in the field. … Repeated fungicide applications are expensive but necessary on susceptible carrot cultivars to maintain crop yield and value.” 

Authors: P.M. Rogers and W.R. Stevenson
Affiliation: Department of Plant Pathology, University of Wisconsin-Madison
Title: Integration of host resistance, disease monitoring, and reduced funigicide practices for the management of two foliar diseases of carrot.
Publication: Canadian Journal of Plant Pathology. 2006. 28:401-410.