Natural Plant Pest Control

Harvesting a pristine crop of arugula, that was covered with row cover upon seeding and is Flea-Beetle FREE!

What is a farmer to do when they have pests snacking on their crops and they can’t (or are opposed to) use chemical pesticides? Truthfully your hands are not tied at all. Modern, natural farmers have so many methods for deterring and conquering pest problems the natural way. This article will discuss some of the methods I have put into practice on my Certified Naturally Grown Farmlet. We will dive into farm design, planning and prevention strategies as well as methods to be used during the growing season and after an infestation has occurred. I’ll link to resources for further exploration along the way too.

My Context

My Farm is situated in zone 6b/7a at an elevation of ~2500 feet here in Virginia.

The farm is Certified Naturally Grown which follows closely the same rules as the National Organic Standards, but differs in its approach to record keeping, fees, and inspection protocols. So, the only approved products for use on the farm are those which are naturally (often botanically) derived, and or are marked with the OMRI badge that certifies they can be used on organic farms. Organic farms are encouraged to prioritize prevention over spray regimens so that is what we do here.

An Ounce of Prevention is worth Two ounces of spray!

Let’s dive into preventative strategies for managing pests naturally. After farming for 20 seasons, I have come to know myself and I am far more likely to implement a prevention strategy than to add something like a spray regimen to the long list of things to do in the middle of summer. As it turns out, prevention goes a really long way and many seasons it can save me from spraying anything at all.

The two aspects of prevention include Farm Design and Crop Planning

Farm Design

How a farm is designed has a big impact on how ‘manageable’ it is in the seasons to come. Some aspects of your design directly impact the manageability of your pest population directly or indirectly. Here are some design choices you can think through as you create your farm.

Protected Culture, aka growing in high tunnels or hoop houses is a great way to combat pest (and disease). This spring, I took two of my three tunnels and decided to use insect screening to block off the sidewall curtains. While this cut down on some airflow, it created a barrier to keep pests out of the tunnel and will stay in place for many years. This method eliminated the presence of cucumber beetles and flea beetles in the summer and allowed me to keep some worms off of my brassicas. Even in the one tunnel I have without the screening I was able to shut the structure down every night and prevent the tomato horn worm from being welcomed in (since their mother is a night-flying moth). In addition to keeping pests out, it can also trap beneficial insects in if you release some of your own.

The idea of having this indoor space that is different from the outdoor free-for-all is special and somewhat easier to manage mentally. But having a warmer space can also harbor pests like aphids into winter and spring and create unwelcome issues. It seems like preventing excess nitrogen in your nursery, and transferring the infested plants to your tunnel is good for prevention.

Baby greens seeded under row covers (right) using both hooped and unhooped beds. As long as danger of frost is not present it is OK to not hoop the beds, but I find them easier to secure in wind when hooped.

Protection can also come in the form of Row Covers- which can keep crops pest free. You can cover one bed width or multible beds wide and stake, weigh, or bury the edges so that the pests cant get in. On my farm this is a common practice to keep the flea beetles from eating brassica greens mixes- I even have to cover them in the greenhouse at times. Its important to put these covers out immediately after seeding or planting for them to be affective and keep the pests from getting locked inside like an all you can eat buffet. Row covers must be handled with care because they can be easily torn by workers, or by harsh winds, whereas protecnet is less likely to be torn because it it stretchy.

Early Spring Broccolini plants in the screened tunnel. No need to use row cover because the screened house kept out the early hatching of cabbage moths. But oops! look closely and these plants got nipped by frost- so row cover would have helped for warming (ha! they did outgrow the damage)

Zinnia planting adds color and lots of pollinator and beneficial habitat!

Beneficial Insect Plantings were part of the first layouts of my farm and the first season I started thousands of perennial plants to help fill them in. Initially I was just planting these beneficial insectary gardens in areas of the farm that were not suitable for growing crops and it became a way to make those ‘lost areas’ a useful part of the whole ecosystem. Certain flowers will not only attract pollinators but also attract natural pests that prey on crop pests. Some examples of beneficial insects are lady beetles, parasitic wasps, and hoverflies. More info available on the link.

Farm Layout also feels important because the landscape itself needs to be able to be maintained with ease. As I planned out the beds, and the fence line I made sure that a 4’ bush hog could fit on either side, or that the riding mower could maintain the grass walkways with ease of turning and with enough width. Without this consideration you may find yourself maintaining the land less and less, weeds that harbor pest species can grow up and become even harder to maintain the bigger they get. Sure the wild grasslands can be great for beneficials but can also harbor pests and moisture.

Crop Rotation is the practicing of moving plant familied to different locations each year so that potatoes, for example, arent planted in the same patch year after year. The larger the farm you have the easier it could be to ‘outrun the pests’ through crop rotation. For example your fields may be 1/4 mile apart and you can put potatoes in one field this year and another field the next. That is a great effort to make and the more uniform your planting beds, blocks and fields are the easier it will be to plan and rotate your crops with ease. The smaller your farm gets, the harder it is to outrun the pests and the more important it is for you to implement the other strategies listed on this page.

Standardization of bed length and width and row spacing is another design element that creates ease for pest and control- when using netting, row cover or other exclusion methods you know what is used on one bed will fit on another and that makes it more likely that you will deploy it easily without too much fiddling and figuring. I find that cutting out the fiddling and figuring out during a farming season is a key efficiency! Standard row spacing makes for easier weed control which will help make scouting for pests easier and your mitigation efforts more timely.

Prevention through planning: Add disease and pest resistant crops into your crop plan too. By design you can build-in resistance based on varieties or crop families that are known to be great contenders in the field. It takes some field testing, farmer interviews or asking your seed reps but this is a great step to add to your ‘prevention bucket’.

Soil Health is also a great way to prevent disease and pest problems. Certain imbalances in the soil will create more or less pest and disease pressures. Amazingly, the healthier your plants and soil are- the less digestible your crops will be to pests and the less mitigation you will have to do. John Kempf talks about this often on his podcast and I recommend a listen if you like to go into the nerdy weeds: https://www.youtube.com/watch?v=WNm08atn6tY

What to do once the pests have arrived?

There are several control methods a natural farmer can use once a pest has arrived on the farm and is doing damage to crops- whether it is munching on leaves causing crops to look ugly, transmitting diseases or compromising the harvestability of the crop entirely. Your options include, benefitial insect release, natural sprays, manual removal, or crop removal.

Beneficial Insects like those sold at Arbico Organics are bugs that have an appetite for things like aphids, cabbage worms, nematodes- what have you! It is important to select the right species for your pest problem, and deploy them in the right quanitiy, time of year, and on a schedule.

Natural Sprays like those sold at Seven Springs Farm Supply are OMRI listed and are applied via Spray, Soil Drench, Dusting, or Fogging. You can see on the product information the crops and pests that certain sprays are approved for. Its important to spray only according to the manufacturers suggestions and follow the rules for harvest interval. Harvest Interval is the amount of time you need to wait after spraying before a crop is harvested for humans (and this is important for the workers who harvest it as well). Although OMRI listed sprays are made from organic materials, it doesn’t mean you want them in your lungs so you still need to wear PPE (mask, gloves, bodysuit). Some sprays require reapplication often, and others are effective with a single use. The crop advisers at Seven Springs are a great resource if you don’t know how to tackle your problem, and extension services can also be a great starting point with identification of the pest and the possible solutions.

Manual Removal of pests means that you pluck each one you see off the afflicted plants and kill them. This is best done with large pests like horn worms, cabbage worms, potato beetles and especially easier before they get too established. It’s less gross if you wear gloves and you drop them into soapy water rather that squishing individually.

Crop Removal might be the only option if an infestation goes bonkers on a crop and it is unmarketable and inedible as a result. You may choose to leave the crop standing as a sacrifice. Or it may be best to clear the plants out and take them to a far away field to decompose or burn. It does happen more often than you think that an entire planting of something is pulled before it ever reaches the market.

A Holistic Approach

As you can see there is not just one solution to a pest problem, but a whole ecosystem of prevention, planning, observation and mitigation. This is how it is with so many aspects of farm life. I often refer to it as an interpretive dance because each situation requires so much interpretation and unique problem solving. I hope this showed you some approaches to Natural Pest control that you did not know about before! Let me know in the comments what natural methods you use on your farm!

Planting baby cucumbers (with baby) on April 1st in the netted tunnel. This protects the plants from Cucumber Beetles which spread bacterial wilt when they nibble on cucumber plants.