Consumers Want Perfect Avocados: Growers Must Spray

Infected Avocados

Avocado Thrip Fruit Scarring

Historically, the production of avocados in California required little usage of insecticides. Avocado pests were kept under commercially acceptable control by a variety of beneficial organisms. This situation changed in 1996 with the appearance of avocado thrips which feed on the surface of the fruit. Feeding scars develop while the flesh of the fruit is a healthy green. Even partial fruit scarring results in downgrading of fruit in packinghouses because of cosmetic damage unacceptable to consumers .

“The California avocado industry is under increasing threat from the introduction of arthropod pests. The avocado thrips, was first detected in California avocado groves in June 1996, and it has since spread to most of the major production areas within the state where it has become the primary insect pest. The main source of economic loss arises from feeding damage that causes scarring of immature fruit, leading to a reduction in fruit quality at harvest.

In California avocado groves, the use of foliar insecticides is the predominant tactic adopted by growers for the management of arthropod pests, including the avocado thrips. Aerial applications by helicopter are needed for the majority of California avocado groves because most are grown on steep hillsides.”

Author: Byrne, F. J., et al.
Affiliation: University of California
Title: Field evaluation of systemic imidacloprid for the management of avocado thrips and avocado lace bug in California avocado groves.
Source: Pest Management Science. 2010. 66:1129-1136.

A Crop Variety May Resist a Disease but May not be Desired by Consumers.

Blight on stems

Blight lesions on chickpea stems

The planting of disease-resistant varieties is often promoted as an alternative to the use of fungicides. If a plant variety is produced through traditional crop breeding and is able to somehow resist penetration and infection by fungi, then fungicides are not needed. Right? The problem is that when new varieties are produced through crop breeding, they often lose quality traits that are desired by consumers. In Turkey, the best quality chickpeas are susceptible to blights and require fungicide treatments in contrast to the lower quality resistant chickpea varieties.

“Chickpea is one of the most extensively grown legume crops in Turkey, the area and production being 622,214 ha and 548,000 tons, respectively. Chickpea blight, is one of the most important diseases affecting this crop wherever it is grown. The disease, which originates from infected seeds and diseased plant debris remaining in the field, mainly affects all the above-ground parts of the plants, causing lesions mostly on stems and stem breakage. Chickpea blight can be effectively controlled by using tolerant or resistant cultivars, but none of them has good quality or sells for high prices in Turkey; unfortunately, high-value cultivars are susceptible to the disease. Seed transmission is especially important where crop rotation is practiced. For this reason, effective chemical control is needed for seed and foliage treatments.”

Authors: Demirci, F., et al.
Affiliation: Department of Plant Protection, Ankara University, Turkey
Title: In vitro and in vivo effects of some fungicides against the chickpea blight pathogen, Ascochyta rabiei.
Source: Journal of Phytopathology. 2003. 151:519-524.

Fungal Spots on Carrots are not Acceptable to Consumers

Carrot Cavity Spot

Carrot Cavity Spot

Cavity spot is a common disease of carrots grown in California. The disease results in a small fungal spot on the carrot, which can be easily trimmed away by consumers. However, this “cosmetic” defect is not acceptable to consumers. If growers do not control cavity spot in their fields by using fungicides, their carrots would have to be sorted manually to remove the damaged ones. The sorting costs are prohibitively high; fields with high levels of cavity spot are simply not harvested…… because of consumer standards.

“Out of the 62,000 acres of carrots grown in California, cavity spot is one of the top three problems that farmers need to worry about. Unlike other vegetable diseases and pests, cavity spot doesn’t cause direct yield losses. It does, however, cause cosmetic damage, which in the world of carrots, is equivalent to yield loss.
Cavity spot is a chronic problem and even growers with the best managed fields know that,” says Jim Farrar, a professor of plant pathology in the Department of Plant Science at California State University, Fresno.
Farrar, who has studied cavity spot for the past several years, along with UC Davis researchers Joe Nunez and Mike Davis, says that most growers can accept some level of cavity spot damage in their fields. But fields with even 5 percent cavity spot damage can cause a real problem.
“The cost of hand-culling carrots in the packing shed can be more than the value of whatever carrots there are to save,” Farrar says, “I’ve seen fields where growers have totally had to walk away from entire crops.”
To deal with cavity spot, most growers apply fungicides three to four times throughout the carrot growing season.”

Author: Lieberman, L.
Affiliation: Writer, Carrot Country.
Title: New Materials and Techniques for Treating Carrot Cavity Spot.
Source: Carrot Country. 2012. Fall:13-14.

Consumers Don’t Want Bugs with Berries, Making Insecticides Necessary

Japanese beetles are often present in blueberry fields and are collected along with the berries at harvest. Because of zero consumer tolerance for bugs in blueberry products, insecticides are necessary to remove the beetles from the blueberry fields before harvest.

“The Japanese beetle, Popillia japonica Newman, is an invasive pest of fruit and vegetable crops, turfgrass, and ornamentals in eastern and central North America. … During the adult emergence period of June to September in Michigan beetles can be observed feeding and mating in clusters on host plants.”

“Much of the food industry maintains a zero tolerance standard for insect contamination at pack-out, which places added pressure on growers of fruit crops such as cherry, peach, plum, and blueberry that may be harvested when beetles are present. The majority of commercial blueberry producers use over-the-row mechanical harvesters for collecting fruit from their fields. This harvesting method does not effectively discriminate between beetles and berries, so adult Japanese beetles are a significant contamination risk in fields being harvested where Japanese beetle has not been controlled.”

“Color sorting technology has been adopted by many large processors to detect and remove beetles, providing >95% removal. Even with these management components available to help minimize the risk of fruit contamination with adult beetles, conventional insecticides remain the primary approach to in-field management of Japanese beetles in fruit crops.”

Authors: J. Wise¹, C. Vandervoort² and R. Isaacs¹.
Affiliation: ¹Department of Entomology, Michigan State University; ²Pesticide Analytical Laboratory, Michigan State University.
Title: Lethal and sublethal activities in imidacloprid contribute to control of adult Japanese beetle in blueberries.
Publication: Journal of Economic Entomology. 2007. 100(5):1596-1603.

The Consumer is Always Right and That’s Why Farmers Use Pesticides

More than 90% of US fresh produce (fruits and vegetables) is sprayed with insecticides and fungicides to prevent rots and yield loss. This spraying also assures that there are no scabs or insect-feeding marks on the produce. Although some consumers would prefer no pesticide residues, many are unwilling to accept any cosmetic damage. You can’t have it both ways—picture-perfect produce requires pesticide use.

“Over 300 shoppers entering supermarkets completed a questionnaire about purchasing certified pesticide residue-free (CPRF) fresh produce. One-half expressed concern about pesticide use on fresh produce. Two-thirds were willing to pay 5 to 10% higher prices to obtain CPRF fresh produce, but were unwilling to accept any cosmetic defects or insect damage.” 

Author: S.L. Ott
Affiliation: USDA Economics Research Service
Title: Supermarket shoppers’ pesticide concerns and willingness to purchase certified pesticide residue-free fresh produce.
Publication: Agribusiness. 1990. 6(6):593-602.