Keep Plant Diseases from Spreading

Summer will soon be upon us and many gardeners have already gotten a jump on the growing season. As the weather gets warmer, the chance of contracting diseases increases, so now is the time to start thinking about disease threats. Once you notice black spots, white spots, or signs of rot in your plants, you’ll need to act fast. Expert gardeners don’t waste time patching up plants that have already succumbed to disease. As Benjamin Franklin once said, “An ounce of prevention is worth a pound of cure.” Let’s dive into both how to treat plants that have succumbed to disease and how to prevent black spot, blight, mildew, and more from affecting your garden.

Biorational controls are safe, eco-friendly means to protect your plants from diseases. They don’t include harsh chemicals, striking a perfect balance between stopping diseases while being gentle to beneficial pollinators, soil microbes nd the plants you wish to protect. You'll want to introduce biorational solutions to your garden before diseases appear. However, if you’re reading this article in a panic while mildew spreads through your tomato crop, it's not too late. Just start treatment as soon as possible. We’ll cover preventative measures for three of the most common plant diseases: black spot, blight, and powdery mildew.

BLACK SPOT

Black Spot is a type of disease that’s famous for maligning roses, but it can infect a wide variety of garden plants. You’ll find that black spot is most potent during the long, hot and humid days of summer. Special care should be taken if you have an extended period (several hours) of rain followed by humid, muggy weather. These are the ideal conditions for black spot. As the name implies, black spot manifests as circular black or dark brown spots (¼ inch or larger) with ragged or fringed edges. The disease will first appear on older growth near the roots of the plants then will spread upward. The leaves displaying spots will yellow before falling from the plant.

To treat a plant infected with black spot, you’ll need to prune the infected leaves and dispose of them. If you compost (and this goes for all diseases), never put infected material into your compost pile. Burn the infected material instead. If that’s not feasible, stuff the infected leaves into your trash and let your local garbage service take them away.

To prevent black spot from infecting your garden, examine how you are watering your plants. Try to only water at the root and not directly onto the leaves and flowers. You can also use a spray like Arber® Bio Protectant to increase a plant’s resistance to fungal infection. This particular product uses a unique blend of giant knotwood extract that boosts protein production and disease resilience.

BLIGHT

Late Blight on Tomato Plant

Blight is an umbrella of diseases characterized by a quick spread time and a similar progression. Blight can affect any type of plant, be it indoor or outdoor, and can be caused by bacteria or fungi. Due to the many types of blight, the first step to treating it is to identify which one has invaded your garden.

Here are some general tips on how to prevent blight from devastating your plants:

• If you’re planting annuals, rotate them each year - don’t plant the same species in the same spot year after year.
  
• Make sure your garden is weed free.
• Keep an eye out for tears and abrasions in your plants - bacterial blights can enter the plant in these incisions. 
• Be careful not to overwater your plants.

Powdery Mildew on Zucchini Plant

POWDERY MILDEW

Powdery Mildew is a frustratingly common disease that infuriates hobbyists and professionals alike. Like many common names for diseases, powdery mildew is a bit of an umbrella term for a variety of similar fungal infections. This disease targets a wide variety of common garden vegetables such as tomatoes, zucchini, eggplant, and squash. However, powdery mildew is typically not fatal to the plant and can be easily treated once identified.

If you see white or gray spots on your plant leaves, that’s a sure sign of powdery mildew. BONIDE® Sulfur Plant Fungicide controls mildew by preventing germination, so it’s more preventive than punitive. However, it’s still a good option to stop the spread of mildew while you work to eradicate it. Organic JMS Stylet Oil is an organic fungicide that kills powdery mildew on contact and prevents further propagation for 10 days after application. Make it a habit to remove dead plant matter from your growing area, especially if you’re in a shaded area with little air flow.

Don't let plant diseases overtake your garden this coming summer. Late spring is the best time to stay diligent and prevention is key! Get a head start with our plant disease prevention products and happy growing!

Grant @ ARBICO Organics 

 

Timing Soil Inputs

Getting your soil right for planting can often leave many growers scratching their heads in confusion. There are numerous options available on the market and knowing when to add inputs to your soil is crucial.

Let’s explore the “WHENs” of soil inputs:

When to test the soil

Before you plant a single seed or buy a product, you need to know what’s going on beneath the surface. A soil test can tell you what your soil lacks or has too much of. Getting soil tests in the fall after harvest or early spring allows you to correct imbalances way ahead of planting time. Testing early gives you time to understand your soil’s nutrient profile, pH, and organic matter content.

For cannabis and other nutrient-hungry crops, regular testing (at least once per season) helps guide mid-season inputs, especially before flowering. Other growers may only need to get their soil tested every three years.

When to add fertilizers and amendments

Whether you want the greenest lawn in the neighborhood or a lush garden this year, adding fertilizers and other soil amendments can make all the difference. Once you have your soil test results back, you’ll be able to make the right fertilizer choices for your particular soil and plants.

You can apply slow-releasing fertilizers in the fall or spring to provide consistent nutrients over time. If you notice that your plants are weak and yellowing, you may need to give them a boost with a fast-acting fertilizer. This can be done every 3-4 weeks during the growing season. However, be cautious when applying fast-acting fertilizers, as they can cause damage and even kill your plants.

Apply any additional soil amendments, such as compost, manure, rock dust, or other minerals, based on your soil test results. You can do this before you start planting or top dress throughout the growing season as needed.

When to add microbial inoculants

There are a number of microbial inoculants you can add to your soil from biofertilizers to biostimulants. However, it’s always best to apply them at the beginning of the growing season so the microbials have enough time to colonize the root zone early and form symbiotic relationships as roots begin to grow.

For transplants, it’s ideal to apply inoculants directly to the root ball or into the planting hole, ensuring close contact with the roots. In systems where the soil has been tilled or disturbed, you’ll want to reapply your inoculants to reestablish the colonies. Growers should also consider reapplying inoculants after using fungicides or sterilizing agents that may kill or reduce the microbes in or on the soil.

In cannabis cultivation, microbial inoculants are particularly valuable during the cloning and transplanting phases. Mycorrhizal fungi can significantly enhance phosphorus uptake and improve stress tolerance, both of which are critical for strong vegetative growth and successful flowering later on. Because these organisms thrive in moist, aerated soils, timing applications with irrigation can also help them establish more effectively.

When to add Beneficial Nematodes

Pests under the soil are often the most challenging. Luckily for growers, they can add an exceptional underground ally-beneficial nematodes-to support their operations. Beneficial nematodes should be applied in when the soil temperatures are between 42°F – 95°F. The warmer the soil, the more active the nematodes, and the greater the protection and results. Also, avoid applying them during dry spells or in full sunlight, as UV rays and dehydration can cause them to die quickly. Water the soil before and after application to help them establish.

Knowing when to apply the nematodes depends on what pest you are trying to control. For example, if you're targeting fungus gnat larvae in greenhouse cannabis or vegetable production, it's best to apply nematodes early in the season or just after transplanting, just before adult gnats start laying eggs. If you're managing root-knot nematodes or root weevils in perennial systems, applications are most effective in late spring when larvae are actively feeding near the root zone. In turfgrass or pasture settings, nematodes targeting white grubs should be applied in late summer or early fall, when young larvae are close to the soil surface and most vulnerable.

Each pest has a specific life cycle stage that’s most susceptible to nematode predation. Proper timing ensures that beneficial nematodes find their targets before they cause significant damage, and before they retreat deeper into the soil where nematodes are less effective.

Final Thoughts

Treat your soil right, and you’ll reap huge benefits in the end. Improving the soil won’t happen overnight, as great soil health starts long before you plant your first seed. By testing your soil early, timing inputs to match plant growth stages, and using biology-based inputs like microbes and nematodes, you set your crop up for long-term success.

So, don’t just feed your soil. Observe and listen to it.  It might just tell you exactly what you need.

 

Pest of the Month: Japanese Beetles

Japanese beetles are the bane of many growers. These voracious pests feed on over 300 plant species, skeletonizing leaves and damaging flowers, fruits, and crops. Their ability to thrive in diverse environments makes them a persistent problem for growers across the United States.

These beetles are an invasive species that originally came to the US in 1916. Since then, Japanese beetles have spread south and west, covering most of the eastern United States and into the Midwest. Today, Japanese beetles continue to expand their range, causing significant damage to both home gardens and commercial agriculture.

Life cycle and biology

Japanese beetles are small beetles with a metallic green and copper color. They will often raise their hind legs in a defensive position to deter predators.

Females will lay their eggs in the soil in late summer, and the eggs will hatch into white, C-shaped grubs. These white grubs eat grass roots and can cause damage to lawns and turf. The grubs will overwinter and continue feeding when the weather warms up in the spring.

As the grubs grow and mature, they will pupate in the soil and emerge as adults. The adults then get to feeding and mating. The beetles skeletonize the leaves of plants, meaning they eat the leaf tissue between the veins.  

Preferred plants

Over 300 plants are on the menu for Japanese beetles. However, they do show a strong preference for certain plants. Some of their favorites include:

• Roses (Rosa spp.)
• Grapevines (Vitis spp.)
• Maple Trees (Acer spp.)
• Apple Trees (Malus spp.)
• Linden Trees (Tilia spp.)
• Corn, soybeans, and other row crops

They also attack ornamental flowers, fruit trees, and garden vegetables. While they feed on a wide variety of plants, they tend to avoid lilacs, boxwoods, and certain conifers.

Methods of control

Since Japanese beetles spend most of their time in the soil and their adult forms are highly mobile, it’s often best to target them in their grub stage.

While trapping has become a popular tactic, this can often bring more adults to the trap and they can spill over onto your vulnerable plants.

Some of the best methods for controlling them include:

Beneficial Nematodes – These microscopic worms target beetle grubs in the soil, killing them before they mature into adults. Check out our Hb NemaSeek nematodes and Sr NemAttack nematodes for grub control.

Milky Spore (Paenibacillus popilliae) – This naturally occurring bacterium infects and kills Japanese beetle grubs, but takes time to establish in the soil. It’s offered in both powder and granule forms.

Need Seed Meal – This neem tree derivative acts as both a soil amendment and a natural pesticide. When applied to lawns and garden beds, it disrupts the feeding and development of Japanese beetle grubs, reducing their survival rates. It also improves soil health, making it a dual-purpose solution.

Suppose you want to target adult beetles that are damaging your plants. In that case, you’ll want to adopt a more integrated pest management approach, combining both cultural and physical strategies with natural insecticide treatments.

Physical control - Removing beetles by hand in the early morning and dropping them into soapy water can help reduce populations in small gardens.

Row Covers – Using fine mesh netting can protect high-value plants during peak feeding periods.

Organic and Natural Insecticides – Using natural insecticides can help control Japanese beetle populations while minimizing harm to beneficial insects and the environment. Some of the best options include:

• Kaolin Clay – This fine clay powder forms a protective barrier on plant leaves, making them less attractive to Japanese beetles. It doesn’t kill the beetles but discourages feeding and egg-laying. Apply it early in the season before beetles become abundant.
• Pyrethrins – Derived from chrysanthemum flowers, pyrethrins are fast-acting contact insecticides that target adult beetles. They work by disrupting the nervous system, leading to paralysis and death. Pyrethrin sprays are best applied in the evening to minimize the impact on pollinators.
• 
  Azadirachtin(Neem Extract) – A key compound found in neem oil, azadirachtin disrupts the feeding and reproductive cycles of Japanese beetles. It acts as both a repellent and an insect growth regulator, preventing larvae from maturing into adults. Look for neem-based sprays with high azadirachtin content for the best results.
  

For effective control, apply these natural insecticides as soon as beetles first appear and reapply after rainfall. Combining these treatments with cultural controls and biological solutions offers the most effective long-term management strategy.

Japanese beetles are a persistent and destructive pest, but with the right management strategies, you can protect your plants. A combination of early intervention, natural predators, and selective treatments can keep their numbers in check. By targeting both the adult beetles and their soil-dwelling grubs, you can break their life cycle and minimize damage year after year.