Eriophyid Mite Control in Garlic Improves Using a Multi-Pronged Approach
Crystal Stewart-Courtens, CCE-ENYCHP Vegetable Specialist
Introduction to eriophyid mites:
Over the last few years more and more garlic growers have noticed their garlic degrading in storage due to eriophyid mite feeding. Eriophyid mites have been an issue in the US and Europe for decades and are considered the most damaging pest of garlic globally. Since they are microscopic, and may lead to increases in other more easily identified diseases, many growers in New York have not been aware of this issue until recently. If this is the first time you are reading about this pest and are curious if this has been an issue in your garlic, there are a few signs you can use to detect this pest, particularly once populations are high.
Garlic that is infested with eriophyid mites will lose weight more quickly than other garlic in storage and infested cloves will begin to shrink and turn yellow or light brown. Early in the infestation the clove surface will change from being shiny to dull, and over time cloves may develop a sparkly or powdery coating.
[Alt text: An image of seven peeled garlic cloves lined in a row. Three of the cloves are darker, a sign of potential eriophyid mite infestation.]
[Alt Text: Three images at different magnification (10X, 32X, 400X) reveal a garlic clove surface infested with Eriophyid mites.]
Understanding the life cycle:
Eriophyid mites may come to your farm on infested seed garlic, but they can also travel on wind, so clean seed is not the key to prevention as it is with some diseases. Generally mite populations remain low in the field, where temperature, soil moisture and humidity limit reproductive rates. Mite feeding in the early season occurs at or near the growing point and may result in twisted, stunted, and off-color leaves. Later leaf growth is generally not affected in New York.
As the garlic matures mites move into the garlic head and live between the clove and the innermost wrapper leaf. The key point at which populations of mites may increase exponentially is during storage, when humidity is lower than in the field and temperatures are moderate. Populations will continue to increase at room temperature indefinitely, so infestations become worse the longer garlic is maintained in this state with no control measures.
Control improves with multiple approaches:
Most growers do not experience eriophyid mite infestations consistently from year to year, so the management plan changes from year to year. One of the yearly control measures that can also improve storage quality is heating the surface of the garlic. At 113° mite eggs are killed within an hour (Courtin et al, 2000). This process should be done with great attention to prevent bulbs reaching the temperature of 120°, at which point waxy breakdown occurs. During this control step you’ll want to make sure you have good air movement around garlic to keep the temperature even, and it is important to complete this step at the end of drying, when the surface temperature of the garlic is no longer being affected by evaporative cooling.
After garlic enters storage it is important to establish a monitoring schedule so that mite infestations are detected early. Varieties which peel more easily such as Rocamboles including German Red and Italian Red are more susceptible to mite infestations than Porcelain varieties such as German White or German Extra Hardy, so monitoring these will likely show you your worst possible infestations. Squeezing garlic to see if it feels like the wrappers are loosening is a good first detection step. Follow up by peeling the cloves to see if the surface has become dull or discolored. You can always send a sample to the Cornell Plant Diagnostic Clinic for confirmation if you are unsure if your garlic is infested.
If you find that garlic is infested, there are two ways to reduce mite populations: predatory mites or temperature reduction. Maximum population growth occurs at 77° and 80-95% RH. As the temperature drops from here, reproduction slows, stopping at 43°. Hence, a moderate infestation could be held static by storing garlic at 43° or lower. If you store cool to cold, remember that the garlic is being vernalized, and will sprout if brought to warmer temperatures. Keep it cold until its being sold or distributed.
If storing garlic at these lower temperatures is undesirable, another control measure to consider is the use of predatory mites. We recently completed a study examining the effectiveness of this option and the results were mixed, indicating the need for additional work to better understand the best timing for a mite release. Encouragingly, the most effective application of mites was at the farm with the highest pressure, though they were not able to completely control the mites.
Next Steps:
Working with predatory mites to improve their effectiveness is a high priority moving forward, and we look forward to working with biocontrol companies to refine best practices for deployment in storage. If you are interested in being involved in any future studies involving the use of predatory mites in storage, reach out to Crystal at cls263@cornell.edu.
Many thanks to Northeast SARE for generous support of this work through two Partnership grants.
Small-Scale Fresh Market Potato Variety Trial Results
Margie Lund and Robert Hadad, CCE Cornell Vegetable Program
This year, the Cornell Vegetable Program planted a potato variety trial focused on commercially available fresh market potato varieties, with the small-scale potato grower in mind. This trial allowed us to test different varieties of potatoes that might be of interest to consumers at farm markets and see how well they perform in a western NY climate. Below we share overall yield results from the trial as well as some details on some standout varieties.
Yields varied between varieties, with Baltic Rose and Eva out-yielding all other varieties, and Red Pontiac performing the worst in the trial (Figure 1).
Figure 1. Marketable yield measured in cwt per acre of all varieties in this year’s small-scale fresh market potato variety trial from highest to lowest yielding. Varieties are color coded according to skin color (yellow, red, white and purple skin, and orange for russet varieties)
[Alt text: Figure 1. A bar graph shows the yield data for 20 potato varieties with potato variety along the x-axis and marketable yield along the y-axis showing the highest to lowest yielding from left to right. The bars are color coded to represent skin color of each variety. The highest yielding variety is Baltic Rose, and the lowest yielding is Red Pontiac.]
Baltic Rose and Eva were the two highest yielding varieties in our trial. Eva (white skin, white flesh) not only yielded well, but was visually nice with bright white skin and consistent sizing. Baltic Rose (red skin, yellow flesh) had some insect damage present, but otherwise was visually nice looking. Blackberry (purple skin, purple flesh) was our highest yielding purple skinned variety, producing deep purple round tubers, though they did show some color variation in the skin. Among the yellow varieties, Vivaldi (yellow skin, yellow flesh) was the highest yielding. Vivaldi was the standout performer last year in the 2022 trial and has consistently been a reliable yellow variety. We also grew two russet varieties, Caribou Russet and Amey Russet, both of which yielded similarly. Caribou is a larger sized russet while Amey is consistently smaller in size, however both presented with some hollow heart. This year we did see PVY in several varieties including Adirondack Red, Algonquin, German Butterball, and Vivaldi.
We look forward to sharing more on this trial and each specific variety in our full report. For questions on the trial and any varieties featured above, or if you would like to be emailed a copy of the full report once it is released, please email Margie Lund at mel296@cornell.edu or 607-377-9109.
Calculating Break-Even Price or Sales Volume, or How Will I Know When the Price is Too Low?
Elizabeth Higgins, Extension Associate, Eastern NY Commercial Horticulture Program
Every farmer has faced a scenario where they wonder if it’s worth planting or harvesting a crop. Knowing the price you need to receive or the volume you need to sell at a given price (or some combination of the two) can be helpful in determining whether or not an enterprise is likely to be profitable. A cost/volume/price analysis is the method that you can use to do this calculation.
To start you first must know the following:
Your variable costs of production.
These are the expenses that you have that are directly related to producing the crop to the point of sale AND that change proportionately with the volume produced. For a vegetable crop those would be your seeds, plants, production labor inputs, chemical inputs, utilities directly used for producing the crop (usually fuel, maybe electricity), cardboard boxes and supplies.
The key concept to understand with variable costs is this: Your variable costs are what it will directly cost you to produce each unit that you sell. If the price you receive is below your variable cost per unit or your total revenue for that crop is below your total variable cost to produce that crop YOU ARE LOSING MONEY FOR EVERY UNIT YOU SELL! Producing and selling more will just dig you further in a hole. You cannot sell more and become profitable. Your only options are to either get higher prices or reduce your expenses.
Your fixed costs (overhead costs) of production.
These are the expenses you have for producing a crop that are not directly/proportionately related to the volume you produce during the production period for a crop. They also include the overall costs of having an operating farm that are allocated among the enterprises you produce. You pay fixed expenses whether you produce and sell one carrot or 10,000 carrots. Fixed costs include the share of the rent (or land cost) attributable to the crop, share of depreciation for equipment used for this crop, insurance for the crop, share of management expense, share of labor expense for overall farm operations, share of marketing expenses, share of overhead administrative expenses, share of other overhead expenses.
The most important concept to understand with fixed costs is this: The more units you sell, the less impact your fixed costs will have on your overall profitability. If your revenue for a crop is above your variable costs of production, you can be profitable if you can sell enough units to also cover your fixed costs of production for that crop. The impact of sales volume on profitability is mostly attributable to your ability to spread your fixed costs over more units.
The price you plan to receive (the market price or your budgeted price).
This is the starting price for the calculation. It should be the price that you think that you will receive, per sales unit, for the crop. It is also helpful to have a sense of the possible range of prices, from the lowest possible price to the highest possible price (these should be realistic).
The volume that you can produce and sell. You should start with the volume that you expect to produce and sell, you should have used this volume in calculating your variable costs. It is also helpful to have a sense of the likely range of volume (high yields vs low yields).
Do the best you can to calculate these items for your enterprise. Many diversified vegetable farms do not have expenses broken out by crop – so do the best you can to allocate your expenses proportionately to the crop using your best judgement and focusing your efforts on the expenses that are likely to be the most impactful to your budget.
You need this data because the Cost/Volume/Price Analysis looks at the interaction between the price, the variable cost of production, the fixed cost of production and the volume sold.
Let’s look at an example. I am growing an acre of carrots that are sold in 50# boxes. I plan to get $14 per box and I plan to sell 750 boxes from the acre. I have looked at prior year expenses and created a budget. I assume my variable expenses will be $7,566 and my fixed expenses will be $1,000. The data is in yellow in Figure 1: Cost-Volume-Price Spreadsheet.
Step 1. Calculate the Contribution Margin per Unit. The contribution margin per unit is how much revenue you have left per unit sold after you subtract your variable costs to produce that unit.
- Revenue Per Unit: total expected revenue / expected units to be sold (in this case 750).
- Variable Costs per Unit: Total variable costs / the number of units to be sold.
- Contribution Margin Per Unit = Revenue Per Unit – Variable Cost Per Unit.
In this example the Contribution Margin per Unit is $3.91. So after subtracting the variable costs, you earn $3.91 for every box of carrots.
Step 2. Calculate Breakeven Sales Volume. This is how many units (boxes of carrots) you need to sell at a set price ($14) to breakeven, given your variable and fixed costs.
- Target Operating Income: The income (profit) you want to receive. For breakeven it equals $0, but you can put in a number if you have a goal.
- Operating Income (profit) = Contribution Margin – Fixed Costs
- Breakeven: Operating Income = $0
- Breakeven Sales Volume = (fixed cost + target operating income) / contribution margin per unit I
- In this example, Breakeven Sales Volume = ($1000 + $0) / $3.91 = 255.62 boxes (at $14 per box). So, if you sell more than 256 boxes at $14 per box you will make a profit.
Step 3: Calculate the Breakeven Sales Price
- Step 1: Calculate the Contribution margin per unit needed to reach target operating income = (fixed cost + target operating income) / number of units to be sold.
- Step 2: Breakeven Sales Price: Add the number calculated above to the variable cost per unit to get the target operating income.
In this example, ($1,000 + $0) / 750 = $1.33 (the new contribution margin to break even). Breakeven sales price is therefore = $1.33 + $10.09 (the variable cost per unit) = $11.42 (if 750 boxes are sold).
The next logical question is: “What combination of price and volume will allow me to breakeven?” This is where having the formulas in a spreadsheet come in handy. I have developed a spreadsheet you can use to do these calculations for your farm. It is available https://bit.ly/cvpanalysis.
Figure 1: Cost/Volume/Price Spreadsheet
[Alt Text: Excel table showing a cost analysis of Revenue, Variable Cost, Contribution Margin, Fixed Cost, and Net Income across per unit sold, by production unit. breakeven volume at expected price. and breakeven price at expected volume. The chart also displays expected revenue across expected sales volume (# units sold), expected price (per unit), expected variable costs, and expected fixed costs.]
To use the spreadsheet, you will put in the Sales Volume, Expected Price, Expected Variable Cost and Expected Fixed Cost for your enterprise in the yellow cells. The advantage of using the spreadsheet is it is easy to generate the table in Figure 2: Breakeven Price at Different Sales Volumes. It already includes the formulas, so you don’t have to remember them.
To use the spreadsheet and create a graph like shown below in Figure 2, change the expected sales volume (yellow cell) and record in the table what the breakeven price is at that volume (blue cell). The line in blue on the graph shows the breakeven point at each combination of price and volume. Combinations above the line are profitable, combinations of price and volume below the line are not profitable. There are limits to the range of prices and volumes. The limits for boxes sold would be a minimum of 1 box for $8,566 which would be the price needed to breakeven if only 1 box of carrots is sold or 1150 boxes (the most I can realistically produce and sell with the fixed inputs I have budgeted for) at $7.45 per box. In order to have more boxes to sell I would need to change some fixed input (land, equipment, facilities).
Figure 2: Breakeven Price at Different Sales Volumes
[Alt text: Image of a graph depicting the break-even price at different sales volumes.]
A related question I have gotten in the past is “what price do I need to get to break even if my variable costs have unexpectedly increased?” An example would be if labor costs unexpectedly go up.
Here is how you answer this question. My prior breakeven price was $11.42 per box if I sold 750 boxes, and my variable costs are $7,566. But you can see in the spreadsheet that if variable costs are below $9,500, I will make a profit, at my planned price and sales volume. But once total variable costs get above $9,500, I would lose money for each box I sell (assuming I am selling 750 boxes at $14 per box). To make a profit I will need to sell more boxes at a higher price to cover my costs. You can use the spreadsheet to change the price, volume, variable cost and fixed cost information to see what price and sales volume combinations will work for your situation.
Figure 3: Breakeven Price at Different Variable Cost Levels
[Alt Text: Image of a graph depicting the break-even price at different variable cost levels.]
If you have questions about this spreadsheet you can reach me at emh56@cornell.edu or 518-949-3722. I will also be teaching an online class this winter, How Profitable will My New Orchard Investment Be? Evaluating Capital Investment Decisions in a Farm Business, that starts on February 23, 2024. You can register at https://enych.cce.cornell.edu/event.php?id=1847. The course will cover this topic as well as how to use other financial tools to make management decisions. The course is appropriate for any type of farm – we just use an orchard as an example.
Virtual Organic Pesticides Bilingual Training
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CCE Orange County, Glynwood, and CCE ENYCHP are pleased to announce our upcoming Organic Pesticides Training. It will be held on Monday, February 5th, 2024 from 6:00 pm to 8:00 pm. This virtual event, conducted simultaneously in Spanish and English, aims to provide farmers, farmworkers, and professionals with the latest knowledge on organic pesticides to promote sustainable and environmentally friendly agricultural practices.
Organic farming continues to gain traction as a sustainable and environmentally friendly approach to agriculture. To address the growing interest in organic pesticides, CCE Orange County, Glynwood, and CCE ENYCHP have joined forces to organize a bilingual training event tailored for those seeking to enhance their understanding of organic pest control methods
Empoderando La Agricultura: Capacitación Bilingüe Sobre Pesticidas Orgánicos
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CCE Condado de Orange, Glynwood, y CCE ENYCHP se complacen en anunciar nuestro próximo Entrenamiento sobre Pesticidas Orgánicos. Se llevará a cabo el lunes 5 de febrero de 2024 de 6:00 pm a 8:00 pm. Este evento virtual, realizado simultáneamente en español e inglés, tiene como objetivo proporcionar a agricultores, trabajadores agrícolas y profesionales los conocimientos más recientes sobre pesticidas orgánicos para promover prácticas agrícolas sostenibles y respetuosas con el medio ambiente.
La agricultura ecológica sigue ganando popularidad como una forma de agricultura sostenible y respetuosa con el medio ambiente. Para abordar el creciente interés en los pesticidas orgánicos, el CCE del Condado de Orange, Glynwood y el CCE ENYCHP se han unido para organizar un entrenamiento bilingüe adaptado para aquelles que buscan mejorar su comprensión de los métodos orgánicos de control de plagas.