They’re Back: Cabbage Maggots Reappear Following Insecticide Restrictions

Cabbage maggots

Cabbage maggots

Damage from Cabbage Maggot

Damage from Cabbage Maggot

Cabbage maggots feed on the roots of cole crops (broccoli, cabbage, cauliflower, brussels sprouts). The maggots destroy the roots and the plants wilt. Cabbage maggots were effectively controlled for several decades by applications of organophosphate insecticides. However, recent restrictions on the use of organophosphates have resulted in less effective control and reappearance of cabbage maggots as a severe pest of California cole crops.

“Cabbage maggot is one of the most destructive pests of cruciferous crops in North America and Europe and has become the major persistent pest of cruciferous crops in the central coast of California. The value of cruciferous crops is estimated at 1 billion USD in California. In the Salinas Valley of California, cruciferous crops are grown in more than 34,398 ha and are valued at >$485.5 million USD. The majority of this acreage has been affected by cabbage maggot. Important crops that are at-risk from cabbage maggot include broccoli, cauliflower, cabbage, broccoli raab, and Brussels sprouts.

Cabbage maggot flies lay eggs in the soil around the base of the plant. A single female can lay about 300 eggs under laboratory conditions. Legless, 8-mm long white-maggots feed on the taproot and affect normal plant development. The most common above-ground feeding symptoms of cabbage maggot are yellowing, stunting and slow growth.

Since 2008, regulatory agencies in the state have enforced stringent restrictions to curb the use of organophosphate insecticides in commercial Brassica crop production, leaving growers with limited options to combat cabbage maggot infestation. Because of the fewer effective IPM options, widespread crop losses to cabbage maggot have been reported from 2008 to the present.”

Authors: Joseph, S. V., and J. Martinez.
Affiliation: University of California Cooperative Extension.
Title: Incidence of cabbage maggot (Diptera: Anthomyiidae) infestation and plant damage in seeded Brassica fields in California’s central coast.
Source: Crop Protection. 2014. 62:72-78.

Dangerous Respirable Dust Increased by Organic Farming in California

Airborne Dust From Cultivation

Airborne Dust From Cultivation

Health effects of breathing dust can be major. When inhaled, small dust particles can travel easily to the deep parts of the lungs and may remain there, causing respiratory illness, lung damage, and even premature death in sensitive individuals. People in California are exposed to unhealthful levels of small dust particles more frequently than to any other air pollutant measured. California farmers have minimized dust emissions by using herbicides to reduce weed populations instead of plowing the dry soil.  However, organic farmers do not use herbicides and cultivate their fields which results in significant increases in respirable dust in California.

“Respirable dust (RD), defined as particles smaller than 4µm diameter, was collected at the implement from 29 farming operations performed for furrow-irrigated tomato, corn, and wheat crop production over a 2-year period. …Among the cropping systems studied, those that required more tillage or land preparation to be performed when the soil was driest produced the most RD.

Cultivation of organically managed corn caused the greatest increase in RD, more than four times baseline.

In the organically grown crops, all operations related to soil structure improvement were performed in the dry fall. The organically grown corn was disked five times and land planed only once in the fall, while the organically grown tomatoes had four disking and three land-planing operations. As a result, the organically grown tomatoes had a much higher RD production. As in 1994, the organically grown crops produced more respirable dust than their conventional counterparts. The RD increase relative to conventionally grown crops ranged from 15% for the organically grown corn to 40% for the organically grown tomatoes.”

Authors: Clausnitzer, H., and M. J. Singer.
Affiliations: Department of Land, Air & Water Resources, UC Davis.
Title: Intensive land preparation emits respirable dust.
Source: California Agriculture. 1997. 51[2]:27-30

Increased Insecticide Use Protects Onions from Viral Infections


Onions infected with iris yellow spot virus

Iris Yellow Spot Virus (IYSV) was first discovered in the 1989 infecting onions in the Treasure Valley of Idaho and Oregon. IYSV typically does not kill plants; however the virus reduces plant vigor and bulb size. Once plants are infected with IYSV, there is no cure. The virus is transmitted to onions by the feeding of an insect: onion thrips. The disease spreads rapidly in fields with large numbers of thrips. Losses up to 100% have been reported. Onion thrips populations are reduced by the application of insecticides in onion fields thus preventing transmission of the disease to onion plants.

Iris yellow spot virus pressure in this region has not been nearly as bad as it was last year, when it wiped out some onion fields. “The virus seems to have been held off well this year,” said Paul Skeen, who farms near Nyssa, Ore. Farmers in the Treasure Valley area of southwestern Idaho and eastern Oregon produce about 25 percent of the nation’s bulb onions and the virus is one of their main production challenges. It weakens the plant and reduces onion production. It can substantially reduce onion bulb size, which is important because larger onions fetch a higher price. The disease is spread to onions by thrips, and Skeen said many growers in the area started spraying for thrips earlier this season and they sprayed more often. Skeen started spraying 10 days earlier and sprayed every seven to 10 days as opposed to every 14-20 as he has done in past seasons. “I’ve got a good crop coming because I stayed on top of it. I think everybody’s been doing that,” he said.

While onion growers in the Treasure Valley area typically start their thrip spraying programs around Memorial Day, many started in early May this year, said Stuart Reitz, an OSU cropping systems extension agent in Malheur County. While onion growers in this area normally make about six applications for thrips in a season, many have made eight or nine already this year and a few are up to 10, he said. “That helped keep the thrips population down,” Reitz said.

Author: Ellis, S.
Affiliation: Reporter.
Title: Onion virus pressure not as severe as last year.
Source: Capital Press. August 8, 2014.

Herbicide Use Conserves Water, Tripling Sorghum Yields


Sorghum Yield: Bushland, Texas

Sorghum is grown primarily in Great Plains states where it is used as a livestock feed. Early grain sorghum production generally involved clean tillage for weed control which eliminated most surface residues. When retained on the surface, crop residues increase soil water storage which increase crop yield. A USDA-ARS laboratory was established in Texas in 1938 and numerous tests have been conducted on ways of increasing sorghum yield in the very dry Texas climate. When herbicides became available and tillage was no longer required for weed control, more residues remained on the soil surface, more water was conserved and sorghum yields increased dramatically.

“In early dryland studies at the USDA laboratories in Bushland, Texas, USA, most residues were plowed under. Residue management for sorghum production received a major boost when improved herbicides and planting equipment became available in the 1960s. Retaining crop residues on the soil surface with no-tillage and improved herbicidal weed control are largely responsible for the increased water conservation achieved since the early 1970s. For 37 studies at the laboratory, preliminary analysis revealed that dryland sorghum grain yields more than tripled from 1939 to 1997. A major increase occurred in the early 1970s when using no-tillage became common. From 1939-1970, mean yield exceeded 2000 kg ha-1 only six times, but exceeded that amount 20 times after 1970.

Soil water content at planting was the dominant factor contributing to yield increases with time. Most increases in soil water content at planting occurred after the early 1970s, when improved herbicides became available and using conservation tillage (crop residue retention on the soil surface) received major emphasis at the laboratory.”

Authors: Unger, P. W., and R. L. Baumhardt.
Affiliation: USDA-ARS.
Title: Crop residue management increases dryland grain sorghum yields in a semiarid region.
Source: Sustaining the Global Farm. Selected Papers from the 10th International Soil Conservation Meeting held May 24-29, 1999. Pgs: 277-282.

Achieving Happiness Is The Primary Motivation for Pesticide Use for African Farmers

African Farmer

African farmer after herbicide spray 

Pesticides are used by farmers to achieve high yields of marketable crops that results in increased income. A team of Swedish researchers set out to understand African farmers’ motivation for using pesticides. What they found was that pesticide use led to higher incomes, less family stress and increased happiness.

“The study focuses on kale farmers in peri-urban of Nairobi. Kale is one of the most widely consumed vegetables in urban areas of Kenya and has high nutritional value while at the same time acting as an important source of income to peri-urban farming households. Kale is a fast growing crop that is susceptible to many pests and diseases thus requires use of pesticides.

The illustration shows that leafy vegetables farmers use pesticides to protect kale from pests and diseases. The motivation for applying pesticides therefore was to ensure that kale was good-looking or had high sensory quality attributes. This in turn attracted more buyers and also met buyers’ demands for aesthetic quality, usually sought-after by consumers. In addition, the use of pesticides protected kale from pests and diseases which increased the quantity of marketable kale thus generating more money or higher profit margins to growers. The consequence associated with making more money from kale production was the ability to meet family or personal needs. These needs include children’s education, and the provision of food, clothing and shelter for the family. …In other words, farmers apply pesticides to protect kale from pests and diseases in order to avoid failure to meet family needs which can fuel disputes and degenerate into health problems. …This finding suggests that kale farmers’ most important motivation for using pesticides in kale production is to live a happy life, free from stress-related diseases.”

Authors: Lagerkvist, C. J., et al.
Affiliation: Swedish University of Agricultural Sciences, Sweden.
Title: Means-End Chain approach to understanding farmers’ motivations for pesticide use in leafy vegetables: The case of kale in peri-urban Nairobi, Kenya.
Source: Crop Protection. 2012. 39:72-80.

Without Herbicides, Cranberry Beds Would Be Overwhelmed by Weeds and Growers Would Go Out of Business

Treated vs Untreated

Herbicide Treated (L) vs Untreated (R)

71 - graph

The leaves of the cranberry plant form a dense mat over the surface. There are no paths through a cranberry bog. Weeds are particularly troublesome in cranberry bogs, since mechanical equipment (such as cultivators) cannot be used. The first synthetic chemical herbicide to receive widespread use in cranberries was registered in 1965 followed by two more in the 1970s. The use of these three herbicides is credited as the most important factor in the doubling of cranberry yields from 1960-1978. The introduction of glyphosate is credited with a steep increase in cranberry yields in the early 1980s.

“Without chemical pesticides fruit quality would be drastically reduced and it would be virtually impossible to economically produce a cranberry crop.

Without some selected herbicides or any herbicide, up to half of the growers would eventually go out of business because it would no longer be profitable to farm when their beds become overwhelmed by weeds in 5 to 10 years.

Without insecticides, fungicides, and herbicides, fruit quality would be drastically reduced. It would be virtually impossible to economically produce a cranberry crop. Ultimately, many growers would go out of business.”

Authors: Mahr, S. E. and Moffitt, L. J.
Affiliation: University of Wisconsin and University of Massachusetts.
Title: Biologic & Economic Assessment of Pesticide Usage on Cranberry.
Source: NAPIAP Report Number 2-CA-94-1994.

Blueberries Turn Into Mummies Without Fungicide Sprays


Spore release cups growing out of blueberry mummy

Mummy Berry Fungus Forming Inside Berry

Mummy Berry Fungus Forming Inside Berry

Four to seven fungicide applications are made per blueberry acre for control of nine diseases of which mummy berry disease is major. The fungus that causes mummy berry overwinters in shriveled mummified blueberry fruit on the ground. In early spring, cup-shaped structures of the fungus grow on mummified berries. Each cup-shaped structure produces an average of 61,000 spores a day for 9 days. Spores infect young developing twigs and flowers. Fungal tissue colonizes the developing berry. Infected berries turn a cream color and begin to dry (mummify); the mummy retains a shape similar to normal fruit and is composed primarily of fungal tissue.

“Mummy berry disease, caused by the fungus Monilinia vaccinii-corymbosi, is a major disease confronting blueberry growers in North America. …Most losses associated with the disease are due to the rejection or downgrading of commercial blueberry shipments that contain mummified fruit.

Management of mummy berry disease requires repeated applications of fungicide from vegetative bud break through the end of bloom in order to mitigate both shoot blight and flower infection.”

Authors: Tarnowski, T. L., A. T. Savelle and H. Scherm.
Affiliation: Department of Plant Pathology, University of Georgia
Title: Activity of fungicides against Monilinia vaccinii-corymbosi in blueberry flowers treated at different phenological stages.
Source: Plant Disease. 2008. 92[6]:961-965.

No Kiwifruit Exports from New Zealand Without Insecticide Sprays

Leafroller Damage to Kiwifruit

Leafroller Damage to Kiwifruit

New Zealand accounts for 33% of the world’s trade in kiwifruit, exporting about US$450 million annually. Kiwifruit production in New Zealand is entirely oriented toward the export market. The domestic market is small and is flooded with fruit that do not meet export standards. In the early days when it was only a minor crop , no sprays were applied. Today, presence of insects, scales, or insect damage can cause rejection of an orchard’s entire crop.

“In the early days of growing kiwifruit in New Zealand it was considered a crop that didn’t need spraying. The very small amount of fruit produced was sold on the New Zealand market without any major problems due to pests or diseases. Predictably as the area planted increased, and more fruit was submitted to the scrutiny of export inspection, more pest and disease problems were encountered and more sophisticated methods of control were required… Kiwifruit are readily attacked by leaf roller caterpillars, and as plantings developed it became apparent control measures were necessary, especially for export fruit.

There are still a few small growers who never spray at all, but their fruit is seriously damaged by leaf roller caterpillars, and there is no chance of such growers being able to export kiwifruit as fresh fruit.

As exports developed in the late 1960s greedy scale was noticed in significant numbers on the fruit and became a problem in meeting international quarantine standards. Greedy scale was not a debilitating pest to the crop, nor was it a problem to local market fruit, but for export fruit it had to be controlled along with the ever present leaf roller.”


Author: Sale, P.R.
Affiliation: Ministry of Agriculture and Fisheries, Tauranga.
Title: The history of pest and disease control in kiwifruit.
Source: Proc. 33rd N.Z. Weed and Pest Control Conf. 1980. Pgs. 110-113.

Too Great a Risk: Organic Rapeseed Growing in the EU

Rapeseed Field

Rapeseed Field

Humans have used oil pressed from the seeds of plants known as rape for thousands of years. The name rape originated from the Latin word “rapum” which means turnip. Oilseed rape has enjoyed unprecedented popularity in the EU since the 1970s due to support from the Common Agricultural Policy. European production of rapeseed plays an important role in increasing EU self sufficiency in cooking oil. Oilseed rape is harvested from about 3 million hectares in the EU. The crop is attacked by a large number of insects and insecticide use is common. There is little organic rapeseed production in the EU because the insects cannot be effectively controlled.

“The demand for organic winter oilseed rape is steadily increasing. Yet in Germany, for example, oil seed rape cultivation is negligible with a maximum cropping area of 4,000 ha. One important reason for this is the occurrence of insect pests, including the cabbage stem flea beetle, the rape stem weevil, the cabbage stem weevil, the pollen beetle, the cabbage seedpod weevil, and the brassica pod midge. Pest-related yield losses – up to total loss of the crop – make the cultivation of organic winter oilseed rape an incalculable risk.”

Authors: Ludwig, T. and S. Kuhne.
Affiliation: Federal Research Centre for Cultivated Plants.
Title: Mixed cropping with turnip rape and natural insecticides: results of field and laboratory trials on pest control in organic winter oilseed rape.
Source: Integrated Control in Oilseed Crops IOBC-WPRS Bulletin. 2013. 96:43-44.

Artichokes (California’s Official Vegetable) Would be Heavily Damaged Without Insecticides

Artichoke Plume Moth Damage

Artichoke Plume Moth Damage

Artichoke Plume Moth Larvae

Artichoke Plume Moth Larvae

In 2013, artichokes were proclaimed to be California’s official vegetable.99.99% of all commercially-grown artichokes are grown in California. The artichoke is a member of the thistle family and was introduced into California in the mid-1800s where it was met by a native insect that had been feeding on wild thistle plants. The insect quickly adapted and began feeding on artichokes and has become known as the artichoke plume moth. Losses result when they feed on artichoke buds and make them unmarketable due to tunneling in the leaves, borings inside the heads, and a blackening of the heads resulting from feeding and frass exudation. Before the introduction of chemical insecticides in the early 1950s, 50-70% of California’s artichokes were unmarketable because of the moth damage.

“Artichoke plume moth (APM), Platyptilia carduidactyla (riley) (Lepidoptera: Pterophoridae) is the most serious and persistent pest of artichokes in California. If unchecked, 70% of the artichoke buds are rendered unmarketable from worm damage. Insecticides are the most important and sole means currently used for the management of this pest.”

Author: Bari, M. A.
Affiliation: Artichoke Research Association.
Title: A potential alternative in the control of artichoke plume moth.
Source: CAPCA Advisor. 2007. October. Pgs. 58-60.