This article was written by Dr. Aaron Wilson, OSU Extension, Ag Weather and Climate Field Specialist

Fig. 1. U.S. Drought Monitor depiction for Ohio as of October 22, 2024.

Dry conditions have plagued Ohioans throughout the growing season this year, with another below average week of precipitation this past week. Since the remnants of Hurricane Helene moved through in late September, ample precipitation has been hard to come by. Several cities are experiencing one of their driest Octobers on record, including Cincinnati and Mansfield (2^nd driest), Dayton (3^rd driest), and Athens and Columbus (4^th driest). Many of these locations have picked up less than three-tenths of an inch. Warmer than average temperatures this week have also notched the drought stress back up, with numerous reports of field fires in west central and northwest Ohio. Certainly, where drought conditions have persisted the longest in southeast Ohio, crop yields are generally below average, pastures have been slow to recover, and producers are still hauling water. As of October 22, 2024, the US Drought Monitor still shows about 8% of the state in D4 – exceptional drought with about 65% of the state still experiencing drought conditions (D1-D4).

If you are continuing to experience drought impacts or to document improvements, you can view and/or submit local reports at the Condition Monitoring Observer Reports page. For a more detailed look at conditions and resources, visit our Drought Response Page or for the latest up-to-date conditions, seasonal outlooks, and monthly climate summaries, please visit the State Climate Office of Ohio.

Fig. 2. Precipitation forecast from the Weather Prediction Center for 8pm Monday October 28 – 7pm Monday November 5, 2024.

Weather Forecast – Again we are expecting a big warming trend early this week, followed by an increasing chance of Halloween rain and a weekend cool down. High pressure will remain in control through Wednesday, with strong southerly wind gusts and high temperatures running in the mid 70s to low 80s. With gusty winds and low humidity, fire risk will be elevated. A few daily record highs are at stake as well. A cold front will push through the region on Thursday. Although much heavier rain is expected across the central states, a solid line of showers and storms will drop 0.25-0.50 inches of rain. After brief drying conditions on Saturday, another system could bring rainn showers back into Ohio for Sunday and Monday. Temperatures will be much colder over the weekend, with highs in the 50s and 60s and lows in the 30s and 40s. The Weather Prediction Center is currently forecasting 0.25-0.75” of rain this week (Figure 2).

The 8-14 day outlook from the Climate Prediction Center and the 16-Day Rainfall Outlook from NOAA/NWS/Ohio River Forecast Center show that temperatures are likely to jump back above average with a robust signal toward wetter than average conditions as well (Figure 3). This is not a pattern we have seen in a while but hopefully represents a step toward long-term drought and soil moisture recovery for the area. Climate averages include a high-temperature range of 56-60°F, a low-temperature range of 38-41°F, and weekly total precipitation of 0.55-0.80”.

Fig. 3. Climate Prediction Center 8-14 Day Outlook valid for November 5 – 11, 2024, for left) temperatures and right) precipitation. Colors represent the probability of below, normal, or above normal conditions.

Cover shot of new pumpkin guide

A new 72-page guide, “A Modern Approach to Crop and Pest Management in Pumpkin – ANR 806”, was published in August 2024 to help both beginner and experienced growers produce a better crop. Thirteen specialists from Ohio State University, Michigan State University and Cornell University worked together to produce this guide which increases awareness of modern IPM practices such as mechanical weed control, cover crops, pollinator protection and negative impacts of certain pesticide mixtures. Basic topics like weed, insect and disease management are also covered, as well as the benefits of natural enemies and a pumpkin enterprise budget to measure overall profitability. In addition to colorful images and layman’s text to explain each topic, QR codes are sprinkled throughout the guide to provide deeper dives on most topics via factsheets, bulletins, websites and videos from specialists around the country. Although the guide was written for growers in the Midwest, most concepts will apply to growers in the Northeast and Southeast regions of the country.

Copies of the guide can be ordered and purchased at your local Extension county office or online at OSU Extension Publishing (https://extensionpubs.osu.edu/a-modern-approach-to-crop-and-pest-management-in-pumpkin/).

Pages of the new pumpkin guide

 Midwest Mechanical Weed Control Field Day Returns!

Last year this event was held in Wooster, OH and it was a great success, with over 150 farmers in attendance. This year the event has rotated to West Lafayette, IN, home of Purdue University if you care to attend. A full day of weeding tool demonstrations, trade show, and cultivation education for both vegetables and row crops will be on display.

Champaign, IL. In partnership with Purdue University, this year’s Midwest Mechanical Weed Control Field Day will take place on Wednesday, September 11 at Purdue University’s Horticulture research station. 

At the morning Expo you can see weeding tools and speak with company reps from manufacturers in the US, Europe, and Japan, and meet the farmers in attendance from all over the region. At the morning education sessions, learn from experienced farmers and university weed scientists from surrounding states. ‘Weed control on the tillage spectrum’ will make the connection between tillage and weed management – with demos and talks on tarping for vegetables and plowing down cover crops with residue management in mind. 

A walk-behind tractor exhibition – ‘Walk-Behind Alley’ – features demonstrations of walk-behind tractors and hand tools. A wide variety of cultivators, hand tools, and the paperpot transplanting system will be shown. You can also visit the trade show exhibit booths to meet other supply companies, like equipment dealers for all manner of machinery, seed, tools, fertilizers, and soils. 

At noon, the field day will break for lunch – an opportunity for farmers to meet and network, or continue looking at trade show equipment and speaking with exhibitors. In the afternoon farmers follow the tractors out to the demonstration field, where corn, beets, and brassicas have been planted especially for the demonstrations. Many 3-point, camera-guided, autonomous, and belly-mounted cultivators and cultivating tractors will be demonstrated in the field and explained by manufacturers. These demonstrations will show how the machines should be mounted and properly adjusted according to crop and soil conditions, and will help farmers visualize how the implements can work on their own farms. 

Row-crop tools in demonstration include precision-controlled tine-weeders and several types of camera-guided cultivators with finger weeders and all manner of other tooling – see all types of knives, hilling discs, etc. Demonstrations will be held in 4’’ corn. 

Vegetable weeding tools include cultivating tractors past and present, a variety of belly-mounted and rear-mounted steerable tools, and cultivators from Japan! 

Registration for this full-day of learning and networking on mechanical weed control is just $75. Registration includes lunch and all the machinery demos you can handle. It is recommended that everyone register early as each year space runs out. 

This event is perfect for farmers and ag advisors who want to: see a particular weeding tool before buying it, learn how to adjust cultivators, see what is new in cultivation, or learn from other farmers. 

Here is the general information for the event: 

When: Wednesday, September 11, 2024 

Where: Purdue University – MEIGS Horticultural Research Farm 9101 S 100 E Lafayette, IN 47909

How Much: $75 (includes lunch) 

Register online at: https://thelandconnection.regfox.com/2024-midwest-mechanical-weed-control-field-day

*Walk-in registration will be available, but lunch and conference amenities are not guaranteed.

Field Day webpage: https://www.thelandconnection.org/event/2024-mmwcfd/

For more info on the event or to register by phone, contact Crystal at crystal@thelandconnection.org or (217) 840-2128. 

Inquiries for interviews on radio, print, and beyond are welcomed – Please reach out to Sam Oschwald Tilton, glacialdrift@protonmail.com, or 414-213-5337

Interested in exhibiting your products and connecting with farmers at the field day? Please contact us

Powdery Mildew Detected – This week marks the first week powdery mildew was detected in the pumpkin plots in South Charleston at the Western Ag Research Station. There have been reports of PM being found a week earlier in Wayne County. At the station, the amount of disease detected in the trial was extremely minor; only three white colonies on ca. 60 leaves, top and bottom leaf surfaces inspected, on July 18. Powdery mildew can multiply in the canopy rapidly given warm and humid conditions so the recommendation is to begin treatment when the first colonies are discovered. Today, nine treatments for the powdery mildew fungicide trial on pumpkins were applied. Major fungicides being tested include Milstop, Cease, Switch, Gatten, Procure and Quintec. Results of the trial will be reported when the trial is completed mid-September.

Striped Cucumber Beetle Update – The summer generation of striped cucumber beetles emerged in South Charleston around two weeks ago and have moved off of the foliage and primarily into flowers at this point in the season. Treatment for beetles in the flowers is not recommended as this will only cause significant harm to pollinators in and around the field, plus cause other issues with pest insects (see below).

Sticky panel with rootworm attractive lure

On a related note, the striped cucumber beetle attractant study being conducted at the Western Ag Research Station is about ¾ done at this point. Of the three attractants being tested for striped or spotted cucumber beetles, none seem to stand out as being hyper attractive to these two beetles. There is one lure that is very effective against the Western corn rootworm beetle, which has also begun to emerge from corn fields in the past few weeks.

Aphid infested pumpkin plant

Green lacewing egg in center of circle

1 black circle around ladybug eggs, 2 circles around golden aphid mummies

Aphids Rising…But Why? – What do you get when you apply a pyrethroid insecticide to a pumpkin field in early July? Answer, most likely a field full of aphid covered plants. Why the surge in aphids? This is attributed to the highly toxic nature of the pyrethroid chemical class to natural enemies in the field that are actively suppressing the aphid population. In the photos, you can see some major aphid predators re-establishing on the aphid infested leaves; ladybug eggs, green lacewing eggs and aphid mummies (evidence of parasitoid wasps). The lesson here is unless you have a known pest to control in a pumpkin field which is over threshold, resist the urge to spray a broad-spectrum insecticide. If a treatment must be made, consider selecting products that are less likely to flair aphids or other secondary pests.

In an IPM context, it is important to protect plants with fungicides from diseases such as powdery or downy mildew when they are detected above threshold. Over the past few years, researchers have begun to understand the importance of not adding both fungicides and insecticides to the same tank mix due to harmful synergies, some that are known and many that are unknown, on pollinators and potentially other insects like natural enemies. For a deeper dive into the negative synergy of mixing fungicides and insecticides, Cornell University recently published this bulletin. https://cornell.app.box.com/v/ProtectionGuide-FieldCrop2023.

Cornell Pollinator Guide

World’s smartest toad?

Amphibian Pest Management? – While scouting for powdery mildew on Thursday, I came across this toad cleverly parked at the edge of a pumpkin flower, no doubt waiting for a juicy opportunity to nab a few beetles or bees. First time I have ever seen this!

The Integrated Pest Management Program along with OSU Extension educators across the state are monitoring five key pests this season. Monitoring sites are set up on farmer’s fields across the state and will be updated weekly.

Brown Marmorated Stink Bug – This insect will not be monitored for until late July. Adults are currently active on a broad range of specialty crops.

Spotted wing Drosophila – A total of eight sites have been set up in Greene, Geauga, Loraine, Adams and Ross counties. SWD has been detected in all counties with individual trap counts ranging from 6 to 184 flies. The threshold for this pest is 1 fly. If this threshold is exceeded and ripe or ripening fruit is present, growers should consider applying insecticides or use other cultural methods to manage the infestation through final harvest. Growers with ripening brambles, blueberries, peaches and other soft skinned fruit should be aware this pest is likely present in all 88 counties at this point in the season. Refer to this factsheet for more information https://bpb-us-w2.wpmucdn.com/u.osu.edu/dist/1/8311/files/2020/11/SWD_Ohio_handout_V20.pdf 

European corn borer – Five monitoring sites are set up in South Charleston (Clark Co.), Fremont (Sandusky Co.), Geauga and Huron Counties. All sites are reporting low moth numbers for the past two weeks, ranging between 0-3 moths per trap per week.

Corn earworm – Eight monitoring sites are set up in Clark, Sandusky, Fayette, Huron, Pike and Crawford counties. Moth counts have fluctuated in the past two weeks between 0-17 moths per trap per week, with the highest moth count in Clark county. As we get later into the season, expect larger migratory flights of CEW to be present in the state, especially around silking sweet corn. If you have a trap that is located near a mature sweet corn field, move it to a soon to be silking field, as CEW moths are preferentially attracted to silking sweet corn over young or mature sweet corn plants.

Squash vine borer – There are 11 counties currently trapping for this pest in Clark, Greene, Montgomery, Fayette, Geauga, Ross, Pike, Seneca, Morrow, Summit and Williams counties. Clark, Greene, Seneca, Williams and Montgomery. Reports for the last two weeks show a general reduction of moths captured per trap per week, ranging between 0 and 5. This insect should continue to decline through the rest of the season. As growers walk and scout fields, be vigilant to identify potential SVB damage on plants to estimate injury.

Growers can access and view the monitoring data directly at this site.
https://docs.google.com/spreadsheets/d/1T4Uk8VKH-fY4qms4FlEwQvz8o1Lxk-t8LLHVz97kxNU/edit?usp=sharing

Initial powdery mildew infestation

Heavy powdery mildew infestation

This article was co-written with Dr. Sally Miller, Emeritus OSU Plant Pathology, updated from 2023 post.

The article is detailed and thorough as OSU has had an active powdery mildew evaluation program for over two decades. Here are the key messages to focus on; greater details of each are further into the text:

1. Mid-July is the time to start scouting for PM; when the first colonies are found, begin treatment.

2. Treat every 7-14 days using hollow cone nozzles at 35-50 GPA with a target of 65 PSI.

3. Alternate FRAC codes (letter/number on top of label) when spraying to reduce PM fungicide resistance. For example spray 1 Quintec (FRAC 13), spray 2 Procure (FRAC 3), spray 3 Quintec, spray 4 Procure, etc. Adding a protectant (FRAC M) like Manzate Pro or Chlorothalonil (Bravo) can be done with every spray and enhances overall PM control; it’s the one exception to the rotation rule.

4. There are many great to good products available for PM control; at least 3 current sources are listed in this article to find products; Sally Miller and Jim Jasinski’s trial results listed below and the Midwest Vegetable Production Guide.

5. Some cost of application data is provided toward the end of the article so growers can pair efficacy with economics to see which suits their production goals best.

General PM Biology
Powdery mildew usually appears on pumpkins and other cucurbits in Ohio beginning in early to mid July. While it has not been seen in South Charleston at the research station yet (Clark County), it has been reported in Wayne County. The pathogen, Psudoperonospora cubensis, does not overwinter in Ohio; infections result from spores blown into the area on the wind.  Powdery mildew is favored by moderate to high temperatures and high humidity. However, unlike most other fungal plant pathogens, it is inhibited by free moisture on the leaf surface.

Signs of infection are small circular powdery growths on either side of the leaf, typically the lower leaf surface first. These spots enlarge and can eventually cover most of the leaf surface and kill the leaves. Stems and leaf petioles are also susceptible, but the disease is not observed on fruit. In pumpkins, powdery mildew may also attack the “handles”, which can be further damaged by secondary pathogens.

Powdery mildew is managed using disease-resistant varieties (powdery mildew tolerant and resistant hybrids) and fungicides. Pumpkin and squash varieties vary in resistance to powdery mildew; in general, the more susceptible the variety, the more fungicide needed. The choice of fungicide is important because insensitivity to overused fungicides is common. It is critical that a fungicide resistance management program is followed. Alternate fungicides in different FRAC (Fungicide Resistance Action Committee) groups, indicating different modes of action against the fungus. Fungicide applications should begin when the disease first appears and incidence is low (rule of thumb: at least one leaf of 50 scouted). Fungicides that are labeled for use against cucurbit powdery mildew can be found in the searchable Midwest Vegetable Production Guide for Commercial Growers. In the Cucurbit chapter, a fungicide table lists recommended products and their efficacy against powdery mildew.

Product Efficacy Trials
Field exposed greenhouse based studies at OSU of efficacy of powdery mildew fungicides in Ohio in 2021 indicated that Aprovia Top, Luna Experience, Inspire Super, Rally, Miravis Prime, Luna Sensation, Microthiol Disperss, Vivando and Procure provided very good control of powdery mildew on pumpkins (see table in color below).  Velum Prime, Cevya, Prolivo and Gatten provided good control of powdery mildew on upper leaf surfaces but poor control on the lower surfaces.

Quintec provided good control in 2021 but in other years and other states has failed due to resistance. Fontelis, Bravo Weather Stik, Merivon Xemium, Pristine, and Torino have been shown to provide poor or variable control in Ohio or other states and are not recommended.

Table 1. Field exposed and greenhouse incubated powdery mildew fungicide results.

Jim Jasinski, OSU Extension, has been running field trials in southwest Ohio at the Western Ag Research Station since 2014 to assess fungicide efficacy against powdery mildew on pumpkins. Yearly results of these trials (2014 – 2023) can be found here toward the middle of the page.

Some effective season long fungicide combinations, based on 2021-2023 data, are shown in the second table below. Some of these fungicides were not effective in the Field/Greenhouse bioassays (table in color), but when paired with a broad spectrum protectant like Manzate, provided more effective control than when applied alone. Most experts suggest adding a broad spectrum protectant fungicide like Manzate to more powdery mildew-targeted fungicides to reduce the risk of fungicide development, boost fungicide efficacy and protect the crop from other diseases. However, programs based solely on protective products such as Manzate or Bravo, do not provide good season long protection so addition of other fungicides is necessary.

Always check the label for the full list of allowed crops, use recommendations and restrictions.

Table 2. Field Based Season Long Effective Fungicide Treatments to Control PM in Pumpkin in Ohio in 2021 – 2023.

*sequential applications for research only, must be rotated per label for grower use.

Spray Costs
While much time and energy is spent determining the most effective fungicides to control powdery mildew, less effort has been focused on the cost of the fungicide program, which is a huge consideration for growers. Below are listed some price estimates for a handful of fungicides. Prices extended to growers hinge on many factors so if the prices at your dealer vary compared to what is shown below, that is normal and to be expected.

Cevya – $5.92/oz (ca. $17.75 per application)

Gatten – $4.03/oz (ca. $24.18 per application)

Procure – $3.75/oz (ca. $30 per application)

SiGuard – $13/qt (ca. $13 per application)

Manzate Pro Stick – $3.60/lb (ca. $9 per application)

Quintec – $3.80/oz (ca. $22.80 per application)

Vacciplant – $1/oz (ca. $14 per application)

Vivando – $2.30/oz (ca. $35.42 per application)

Luna Experience – $5.15/oz (ca. $30.9 per application)

Microthiol Disperss – $1.85/lb (ca. $7.40 per application)

Pumpkin Enterprise Budget

The Pumpkin Enterprise Budget below is the product of team work led by Eric Richer, Associate Professor, Farm Management, OSU Extension and supported by Jim Jasinski, Professor, Integrated Pest Management, OSU Extension, Rob Leeds, Assistant Professor, OSU Extension-Delaware County, Logan Minter, Associate Professor, OSU Extension-South Centers and Barry Ward, Leader, Production Business Management, OSU Extension.

For more than two decades, Ohio State University Extension educators and faculty from Plant Pathology, Entomology and Horticulture and Crop Science, have supported the production and pest management needs of pumpkin growers throughout the state. The focus of this work has predominately been to help growers produce a better quality and higher yielding pumpkin crop based on solid production and IPM practices. To complement our focus on production, we have developed a new tool to help growers understand the financial aspects and profitability of raising pumpkins in Ohio.

Screenshot of overall budget spreadsheet

For the first time in 25 years, an updated Ohio Commercial Pumpkin Enterprise Budget has been released on the Farm Office website! This downloadable interactive spreadsheet (www.go.osu.edu/commercialpumpkinbudget) can be used to predict your cost of production; calculate profit per acre, per ton, and per bin; and help growers set prices accordingly.  The tool was developed and refined by OSU Extension Specialists, educators and growers over the past few years who have a passion to understand the economic aspects of pumpkin production.

The budget is based on a standard jack-o-lantern production enterprise with three default yield and cost columns based on low (5 tons/A), average(10 tons/A) and high production systems (15 tons/A).  The spreadsheet is designed so growers can enter their individual information in yellow cells and the resulting calculations in blue cells will determine their cost of production and potential profitability. Current market prices for input costs (fertilizer, labor, pesticides, etc.) were used based on industry standards.

Receipts section

The budget begins with a Receipts section that allows growers to break out their production by retail, wholesale or other sale methods based on percentage of yield.  The receipts section also allows for percentage spoilage and customization in price per market segment.

Variable costs section

In the Variable costs section of the budget, growers can input their desired row spacing (between row and in-row spacing) and projected seed costs. The default seeding and fertilizer rates are based on the Midwest Vegetable Production Guide but can be modified per the grower’s production practice. The herbicide, insecticide and fungicide application sections are perhaps the most improved from our last iteration. Growers can utilize the standardized pesticide recommendations and updated industry costs or choose to modify the pest management program based on their current production practices, farm history and seasonal pest levels. Also included are custom spraying charges in case a grower does not spray their own pumpkins.

The remaining Variable costs include bee hives (if used), labor, marketing cost of bins, trucking, fuel/oil/grease, repairs, irrigation, and operating interest.  These costs can vary greatly by grower, but standardized values were used where standardized costs could be found.

Fixed costs section

After variable costs, the budget tool estimates Fixed or overhead costs related to operating a commercial pumpkin enterprise.  As in most enterprise budgets, these Fixed costs include owner’s labor and management charges, machinery and equipment ownership costs and a land charge. Again, producers can enter their individual values for each of these categories if they know them for a more accurate output.

Total costs section

The Total Costs section at the bottom of the budget helps growers determine their overall costs on a per acre, per ton and per bin basis depending on actual pumpkin harvest yields.

The last six lines of the Total Costs section are used to understand profitability. These are broken down on a per acre basis into Returns Above Variable Costs, Returns Above Variable and Land Costs, and Returns Above Total Costs. Growers generally associate Returns Above Total Costs as their profit per acre. There are more sophisticated measures of profitability such as Return to Land, Return to Labor and Management, and Return to Land, Labor and Management if growers care to dive deeper. The “Return Above” and “Return To” measures of profitability are explained in greater detail in the footnotes associated with the budget.

If you have specific questions about the Pumpkin Enterprise Budget, please contact Eric Richer, richer.5@osu.edu.

Pumpkin Enterprise Budget video

If you prefer to digest this information by watching a video where Eric explains the various budget sections, it can be viewed on the OSU IPM YouTube video library here: https://youtu.be/RkNMqGezVaU?si=7eMSTxx5xPU5q5Qs

Additional crop and animal enterprise budgets can be found on OSU’s Farm Office website at www.farmoffice.osu.edu/farm-management/enterprise-budgets.

Screenshot of OSU IPM YouTube video library

To view the pumpkin IPM video library created to help growers identify and manage key pests and other topics, check out go.osu.edu/osuipm.

This article was excerpted from the CORN newsletter #19 and written by Alyssa Essman, Assistant Professor, Extension Field Crop Weed Specialist, Dept. of Horticulture and Crop Science.

We’re entering a period of hot, dry weather and the long-term forecast for this season suggests that these conditions are likely to persist during the summer and through harvest. With variable planting dates across the state, there is also a range in current crop growth stages and overall status, which means there are also different weed management activities taking place over the next month. There are some considerations to keep in mind as we aim to manage weeds when temperatures are high, and rainfall is scarce.

• Residual Herbicides – The incorporation or activation of residual herbicides can be insufficient in areas that receive less than ~ 0.5 to 1 inch of rainfall. Without some sort of incorporation or activating rainfall, the product does not enter the soil solution and is not available for uptake by germinating weeds. A layered residual strategy for the control of waterhemp is still recommended, especially where crops were planted early and preemergence herbicides are starting to decrease in concentration and lose efficacy. Rain will still be needed to incorporate these later-applied residual herbicides into the soil profile for maximum efficacy.

• POST Applications – Plants respond to drought stress in part by increasing the thickness of the cuticle, or the waxy outer layer of the leaf, to preserve water. This can result in decreased herbicide absorption, and translocation and metabolism within the plant are also affected. Systemic herbicides are especially at risk of reduced efficacy in these conditions. The use of the right adjuvant product and rate can help to increase absorption by improving leaf coverage and product uptake. Follow the label and herbicide/adjuvant manufacturer recommendations to determine the best adjuvant type and rate in these conditions. Some labels also include specific information related to applications in dry weather. Be aware that an increase in activity from the use of adjuvants can also lead to increased crop injury, and that applications early or late in the day may reduce the risk of injury. Contact herbicides are also more active when applied during hot weather, and crop injury from applications of these products may increase as well. Where residual herbicides were less effective due to lack of rainfall, a two-pass POST program should be considered to manage the potentially higher weed densities.

• Weed Emergence – Dry conditions can delay the emergence of weeds to some degree, especially those in the upper portion of the soil, and those that emerge from smaller seeds. Larger seeded species and those at lower depths will be less affected, as they have more energy reserves and access to more water for imbibition and growth, respectively. In dry weather patterns, weed emergence flushes may occur periodically following rainfall events.

• To Wait or Not to Wait – One question that often comes in when rainfall is limited is whether it’s better to apply POST herbicides soon, when weeds are smaller, or to wait until after a rain event and the potential following flush of weed emergence. Weeds are most effectively controlled when they are smaller and are actively growing. Drought and heat stress can impede control efforts and herbicide efficacy, and large weeds are more difficult to control. This is especially true if the stress-inducing conditions persist and weeds “harden off”. For this reason, it is a good strategy to wait for the extremely high temperatures to pass before making an application, for greater crop safety and herbicide efficacy, and to ensure weeds are actively growing. However, it’s not necessarily better to wait for a rain before making a POST pass. As mentioned, plants that persist through hot and dry weather often produce thicker cuticles, and it can be difficult for herbicides to get into the plant and be effective. For this reason, it might be best to spray when weeds are as small as possible unless there is some definite rain in the forecast.