Joseph M Hannan
Production Instructor
Center for Arkansas Farms and Food
07.01.2024
Edited by Luke Freeman
Introduction
It’s mid-season in Arkansas. Summer is here and so are all of the insect pests! Japanese beetles, cucumber beetles, cabbage moth, tomato fruit worm, Colorado potato beetle, leaf hoppers, stink bugs, harlequin bug, tarnished plant bug, squash vine borer… you name it we have it! This is also the time of year when row covers and insect netting become less effective due to the size of the crop, ongoing harvest, and heat.
In short, this is the time of year when the best horticultural practices alone are no longer effective at maintaining clean product and assistance is needed from organic insecticides. Fortunately we have quite a few products available for certified organic production. However, they each have their own quirks and limitations and no one product is a silver bullet. Soft-bodied flies and worms can be effectively managed with a variety of organic products while hard-bodied insects have the fewest options available and are more difficult to control organically
Pyganic or Pyrethrin 
Pyganic and its generic pyrethrin alternatives are commonly found on organic farms for a couple of reasons: one, it actually works; and two, it works reasonably well. It has broad spectrum control across a wide array of insects including aphids, white flies, beetles, and worms. It is very indiscriminate on what it kills, which is both a good and bad thing. Pyganic will kill insect pests but it also kills beneficials. The other pitfall with Pyganic, like most other organic pesticides, is that it has no residual control. It breaks down in the environment and becomes inert very quickly. For Pyganic to truly be effective, you need a good sprayer that can really push product into the plant canopy and reach the top and bottom side of the leaves. Pyganic needs to actually touch the insect during that spraying process. If an insect flies out of the field while you are spraying and then flies back into the field a few hours later, it will not be controlled. This is why a lot of people don’t think Pyganic is working for them. It is likely because they had poor coverage and didn’t get the insecticide into the plant canopy to reach the insects or new ones flew into the field.
To increase your effectiveness with Pyganic, and many other products, increase the gallons of water used. More water increases the likelihood of reaching the pest (at the downside of more water and time). The Pyganic 5.0 label calls for a minimum of 2 gallons of water per acre. Unless you have a very high-quality air assisted sprayer, this simply isn’t enough water volume to be effective. Twenty-five gallons of water per acre at full crop canopy is much more appropriate with simple nozzle type sprayers. For those with simple nozzle-type sprayers, adding fans to your sprayer can help agitate leaves and spread product into your plan canopy.
Small hand-pump pressure tank sprayers are going to be your worst tool for pest management. A battery or gas-powered backpack sprayer (such as the Ryobi One+ 18v or 40v or Makita 18v backpack sprayers) will be better. But the best option would be an air-assisted sprayer such as the Stihl SR200 backpack sprayer because it includes a fan to blow and agitate. If you are looking for a new sprayer, look for something with a fan or air assist for best performance if you can afford it.
If you are reaching for Pyganic, you likely are targeting a mobile insect which means that spot spraying will be insufficient. Hard-shelled adult insects such as cucumber beetles, stink bugs, and harlequin bugs are difficult to control regardless. Also know that 100% control with 1 application is unlikely. When purchasing Pyganic, be sure to read the label and verify that it does not restrict commercial use. If the label states “not for commercial use” or similar, this means that it cannot be used on crops that are grown for sale. Bonide brand Pyganic is a prime example here. Also remember that you cannot apply Pyganic twice in a row in the same field. You must rotate to a different class of insecticide before you can spray Pyganic again. This could look like switching between Pyganic and Neem if making multiple applications to control a specific pest in the same field.
Neem
Neem is a complex oil extract from the Neem tree. It contains azadirachtin + oils. It’s a broad spectrum insecticide with fungicide claims though I don’t know of anyone using it as a fungicide or any major trials verifying its fungicide efficacy. Like Pyganic, it controlls a wide range of insects, has no residual control, and is a contact kill only. It must physically contact the pest you wish to control so similar best practices as Pyganic are recommended for application. Because Neem is an oil, direct sunlight with high temperatures following application can cause some burning of the leaves. It is best used on cloudy days or during the evening to minimize risk of crop injury.
Neem + Pyganic makes an interesting pair. It seems that they work synergistically when mixed together in a tank and applied together. This is a case where 1+1 > 2. However, the combined products are expensive and limit rotation options when using Pyganic.
Aza Direct
Aza Direct is the azadirachtin-only portion of neem oil. Everything else from the neem oil is removed. It works as a feeding inhibitor and repellant. It can have 24 to 72 hours of effectiveness under ideal conditions before it needs to be reapplied. While it technically has broad spectrum control, Aza Direct has limited use-cases since it doesn’t actually kill the insect pest. It is probably best used to keep a targeted pest off a ripening crop that will be harvested the next day. For instance, you might use it to keep multicolored Asian lady beetle (MALB) off grapes in the fall.
M-Pede
M-Pede is an insecticidal soap, which are derived from animal fats and plant oils. Soaps have broad-spectrum control but predominately work on soft bodied insects such as aphids, spidermites, and whiteflies. If you have a high tunnel, you should have M-pede on your shelf. It is one of the most effective (considering cost and efficacy) options for these types of insect pests. As you might expect, soaps are contact-kill only and have no residual activity. However, most of the soft-bodied insects are not very mobile, which means that spot spraying is highly effective. If you are targeting aphids, spider mites, or white flies, keep in mind that soaps DO NOT kill eggs. You will need to make multiple repeat applications to control the new egg hatches. I generally recommend spot spraying every 2 or 3 days for 3 to 4 applications to catch all of the egg hatches. The nice thing is that this is just a localized spot spray so there is minimal risk to nearby beneficials.
Horticultural Oil
Horticultural oil (and I am sticking to a generic name here because there are a TON of them) are lightweight mineral- or vegetable-oil-based products. They perform similarly to soaps in that they are broad spectrum, contact only, and work best on soft-bodied aphids, spider mites, and white flies. Like all oils, they can cause leaf burn under warm, sunny conditions – so apply on cloudy days or in the evening. As with soaps, multiple applications of horticultural oil every few days may be needed to control aphids, spider mites, and white flies.
Occasionally soaps don’t work for people trying to manage soft bodied insects. When that happens, I usually suggest horticultural oil and that seems to do the trick.
Entrust
Entrust, otherwise known as spinosyn or Spinosad, is a very unique product and is the first one on our list that has residual activity, meaning it can keep actively killing insects for 3 to 5 days AND is at risk for resistance build up.
Entrust provides very good control against caterpillars, flies, and beetles. It is considered fairly broad-spectrum, but not as much as Pyganic; and it has a fairly short reentry interval (REI) and preharvest interval (PHI). Because of these factors, Entrust is commonly used in fruit crops to control spotted winged drosophila, worms, and beetles that would normally infest ripening fruit. However, overuse of this product presents the risk of insect resistance. There are limitations to the number of times Entrust can be applied to a field and total amount of product that can be applied to mitigate this risk. And like Pyganic, it cannot be used twice without rotating to another product with a different mode of action. It is common to see an Entrust – Pyganic – Entrust rotation used for challenging pests on organic crops. Entrust is expensive, however, and should be used only with high-quality sprayers.
Bacillus Thurengiensis (BT)
Most everyone is familiar with the worm killer Dipel, the most common form of BT. Bacillus thurengiensis Kurstaki is one type of Bt, a bacteria-based insecticide. It is very effective at controlling caterpillars and has a few days of residual activity. Dipel is commonly used against tomato hornworm, tomato fruit worm, cabbage loopers and other worms. If worm control is your intention, then BtK is has the greatest efficacy and is the most cost-effective option. Bt K, or Dipel, is a bit different than many other organic insecticides. Dipel must be ingested by the worm. Once ingested, the worm will stop eating and damaging the crop though it may take some time for the worm to actually die.
Plant Extracts or Essential Oils.
Plant extracts and essential oils can also be used for insect control. All essential oils have similar efficacy towards targeted insects as horticultural soaps and oils. They work best on soft-bodied insects. You can buy or make your own extracts for use as an insecticide. Plant extracts are largely unregulated with a few exceptions. Citronella, for example, is a commonly used repellant but is not allowed for use on food crops You can see the full list of Active Ingredients Eligible for Minimum Risk Pesticide Products from the EPA online and whether or not they can be used on food crops.
If you are making your own essential oil extracts for use as a pesticide, the plants you are growing for extract should be grown using the same safe food production practices that you would follow for growing produce.
Peppermint
Peppermint is primarily a repellant but may have some killing action against soft-bodied insects like aphids and spider mites. I often find peppermint mixed with rosemary or thyme offering a synergistic effect in research reports and commercially-available products. It is an oil so there is risk of burning; and it requires multiple applications like other oils for complete control.
Rosemary
Rosemary works best on soft-bodied insects and, from talking to people that have used it, seems to be effective in both research trials and on-farm trials. Kemin Industries makes TetraCurb and TetraCurb Max, which have rosemary oil as their active ingredient. I have found some other commercially-available products that contain rosemary and thyme but their labels did not include food crops.
Summary
There are many effective options for soft-bodied insect control in organic fruit and vegetable production; many of which are soap- or oil-based products. However, there are very few organic options for hard-shelled insects such as cucumber beetle and harlequin bug. Selecting the right product and using it correctly is critical for success; in addition to understanding that 100% control may not be feasible with organic insecticides under high pest pressure, especially when combating hard-bodied pests. The number of certified organic pest management tools is steadily increasing as certified organic market share increases. Many products available on the market today are not listed in this article and that is not a slight against them. For the products not included in this article, I simply don’t have enough information on their efficacy or best practices on their use in Arkansas.