IPM: Yellowing Hemp Leaves? Lots of Reasons but Always Check pH of Soil and Water

 Yellowing of the lower leaves in hemp plants can be caused by several factors, and it's important to identify the correct one in order to address the issue effectively.

Yellowing Hemp Leaves caused by root zone pH being too high.

We try and provide the optimal growing conditions here at Arendell Hill Nursery in Tallahassee. Yet sometimes, no matter how intentional we are with organic nutrient application, good soil texture, adequate drainage, proper sunlight exposure and continual IPM we still encounter problems with plant growth.

Lately I've been seeing a bit of lower leaf yellowing on some of our container grown hemp plants. I know they have been properly watered and fertilized however the yellow seemed to be persistent.

There are many cultivation variables known to be responsible for yellowing hemp leaves.

Here are some common causes:

1. Nutrient Deficiency: This is often the most common cause. In particular, nitrogen deficiency can lead to yellowing of the lower leaves because the plant moves available nitrogen to support new growth at the top. Other deficiencies that can cause yellowing include potassium, phosphorus, and magnesium.

2. Overwatering or Underwatering: Both of these can stress the plant and cause yellowing. Overwatering can lead to root rot and oxygen deprivation, while underwatering can cause the plant to become dehydrated.

3. pH Imbalance: Hemp prefers slightly acidic to neutral pH levels (around 6-7). If the pH is too high or too low, it can lock out essential nutrients and lead to yellowing.

4. Poor Drainage: If your hemp plant is in a pot or soil with poor drainage, it can lead to waterlogging and oxygen deprivation for the roots, causing leaf yellowing.

5. Pests and Diseases: Certain pests and diseases can also cause leaf yellowing. For instance, fungus gnats can damage the roots and lead to yellowing of the lower leaves.

6. Temperature Stress: If the temperature is too high or too low, it can cause stress to the plant and result in yellowing.

7. Light Burn: If the plant is exposed to too intense light, it can "burn" the leaves and turn them yellow.

In our case the yellowing was a result of our irrigation water's naturally high pH of around 8.0 to 8.5. High pH water can, as mentioned above, prevent the hemp plant roots from taking up nutrients, even if those nutrients are available and exist in plentiful quantities within the hemp plant's root zone.

Irrigation pH balancing involves taking into account acidic rainfall amounts and then pH of natural irrigation water. During droughts, when more higher pH irrigation water from the well is used, more 'pH Down' (a water acidifier we use) must be added to irrigation to keep the root zone pH around 6.0-6.5.

When we have periods of significant rainfall, the hemp plant's root zone is less likely to exhibit a higher pH simply because we are using less well water.

Portable, battery powered pH meters are an important tool for Florida hemp growers (and any gardener for that matter). Here is a link to the pH meter we use.

Remember, identifying the exact cause requires observation and sometimes a process of elimination. Always consider the overall growing conditions including light, temperature, humidity, and the plant's watering schedule. If you're growing indoors, you can more easily control these factors compared to outdoor growing.

Asian Lady Beetles and Organic Hemp (Cannabis) Cultivation

 I've been seeing Asian lady beetles, Harmonia axyridis, almost everywhere lately (early February 2022).

Asian Lady Beeetle, Harmonia axyridis, exotic insect and Organic Hemp Cultivation

Though they do little direct harm to cultivation (they do eat aphids) these exotics can cause serious nuisance issues around plants and especially in buildings. They certainly are not my preference for natural IPM across the hemp farm as they compete with native lady beetles.

Asian Lady Beetles on pepper plants at a local Tallahassee Nursery

Mostly, I tend to ignore them because they do not rise to the nuisance level of a 'key pest'. Beware though the Asian lady beetles can bite humans and they do leave a yellowish staining, foul smelling excretion when congregating in and around building windows.

Asian Lady Beetles should be monitored however across the hemp farm for potential damage

All in all, I'd rank them as a low species of concern, one worth notation (I certainly would not want too many of these insects foraging in plant flowers and buds) but not worth immediate worry over, across the hemp farm.

January Fungi, Florida Hemp Cultivation Integrated Pest Management

 Fungi play an important part in our integrated pest management program. Tracking fungi appearance and location is an important part of the organic matrix at Arendell Hill. January fungi under live oaks, coral fungi, Ramaria sp. considering R. formosa. Leon County

Tracking fungi across Hemp Cultivation area helps us understand the role fungi play in pest control 

Organic Hemp Cultivation, Pests in the Leaf Litter

 Caterpillars, when their population numbers grow unchecked, can devastate a hemp or cannabis crop in a matter of hours.

Organic Hemp Cultivation Pest Control, Managing Eastern Tent Caterpillar Web Masses

Last year there was a significant population bloom of the Eastern Tent Caterpillars, Malacosoma americanum in east Leon County.  The thick, web masses began to appear during spring and continued to grow in size through summer into autumn, finally falling to the ground with winter winds and rainstorms.

Here across Arendell Hill we counted thousands of the Eastern Tent Caterpillars over the course of the growing season.  They would crawl down from the safety of their web nests, across the ground and find any number of plants, including trees, to feed on, devouring blossoms, buds and leaves alike.

Our Myers lemons were hit especially hard from hungry caterpillar appetites.

Arendell Hill Nursery was not the only place infested with an over-population of the M. americanum, I encountered significant numbers of these caterpillars all across the city.  Park benches placed around our local library green space were often covered in masses of M. americanum.

As autumn leaves fall, so often do Eastern Tent Caterpillar eggs.  Their eggs are usually laid en masse around twigs, at the base of leaves. Winter storms often blow these egg masses to the ground where they become mixed with leaf litter and await warmer weather before hatching.

An important part of any organic based integrated pest management program is prevention.  One way to control on-site Eastern Tent Caterpillar populations is through daily ground surveillance.  Make it a habit to be on the lookout for fallen egg or web masses.  When you come across the eggs or webs on the ground, pick them up, place in a trash bag, tie securely then drop the bag into the garbage can for landfill destination pick up.

Chances are the web masses may not actually contain eggs but chances are also they may.

Eastern Tent Caterpillar egg and web masses blend in well with fallen leaf litter.  With a little practice one can soon find these well camouflaged potential future pest masses and begin disposing of in a convenient refuse container.

Much of the time the most successful organic pest control practices spring forth from common sense practices and an understanding of pest insect and bug life cycles.

Controlling Eastern Tent Caterpillars before they hatch is much easier than battling hoards of hungry pests. 

Developing an Ecosystem Matrix for Hemp Cultivation, Organic Integrated Pest Management

 In the last several posts we've introduced the concept of ecosystem matrices into our discussion of organic integrated pest management (OIPM).  A balanced ecosystem exists when all of the many existing biological and geophysical entities are functioning in equilibrium with themselves and each other.  This seamless functioning forms the basis of an organic integrated pest management approach for the hemp farm.

Balanced ecosystems function efficiently.  Throughout deep time nature has refined how ecosystems work so that all life within an ecosystem has a place, function and role to play.  Within the biological and geophysical parameters of a balanced ecosystem, all life forms carry out predictable, functional duty.  Change does occurs but in a measured sense.  Functional ecosystem homeostasis is usually maintained on a rolling basis.

However, when the ecosystem becomes unbalanced some life forms may become overly dominant, consuming and damaging to other ecosystem entities.  Hemp farm pests such as certain caterpillars for example may play an important role in a balanced ecosystem yet in the absence of normally present control factors and predators, such as fire or birds, may experience such a rise in population numbers that they disrupt the predictable garden homeostasis and cause uncontrolled damage to crops.

The key to maintaining ecosystem homeostasis begins with an understanding of the hemp growing areas' biological and geophysical dynamics.  What fungi, plants and animal live on and use the hemp farm land? What are the typical weather trends including rainfall amount and wind characteristics?  What is the soil comprised of? How is the air quality? Every life form and geophysical variable that interacts with other farm life forms and geophysical parameters becomes an important part of the ecosystem matrix flux.

A good start to understanding ecosystem matrices begins with a list of what exists and what is happening across the growing area.  A hemp farmer who has a good understanding of his or her farm's ecosystem matrix should be able to jot down a relatively comprehensive bullet list of their garden's parameters .  This list will represent the existing site variables.  The existing state is a reflection of the site in the present moment.  The list  of existing site parameters will usually be somewhat different than the site's historical, or intrinsic list of what has previously existed and happened across the site previous to human development impacts.

This list should evolve into an ongoing effort in identifying the hemp farm's ecosystem variables, much like a diary.  The process of journalling identifies plants, animals, insects, weather conditions, sunrise and sunset times, weather events such as snow, rain and wind, and other variables.  The hemp farm ecosystem matrix variable journal can be developed over time by notation of observed variables into a notebook, on a phone or the computer.

The hemp farm journal will become more and more accurate and comprehensive over time as documentation accumulates.  Certainly collection of data requires a focused effort.  Day in and day out the hemp farmer must record what they encounter during the day.  Often, the most seemingly insignificant events can many times be the trigger that exerts influence over pests.  Many times these trigger events can go unnoticed, all the while supporting an increased pest presence.

As the amount of information in the journal grows, the usefulness of the data increases.  For me, the key to understanding volumes of hemp farm journal data is found in how the data is presented.  The journal's daily entries need to be arranged in a visually coherent manner to be most relevant and useful.  Once the raw data is compiled into a logical presentation, relationships between pest damage and ecosystem matrix variables can be more easily identified.

Although any collected data can be useful to the hemp farmer, a comprehensive journal will contain a minimum of one complete years observations.  A multi-year hemp growing journal will contain invaluable information that can provide worthwhile tools to the grower.

There are several approaches to organizing hemp farm existing matrix variables.  Table format is one way and graphs are another approach.  As a visual learner I do best with data arranged in graphic presentation.  There are any number of ways to arrange hemp farm ecosystem matrix data and while developing the existing ecosystem matrix variable list it is worthwhile to also research what the site's historical (intrinsic) ecosystem matrix might have been like.  Sometimes, on non-disturbed high quality successional or native forest sites there will be few differences between the existing ecosystem matrix or matrices and the intrinsic, historical ecosystem matrices. 

Across farmed, agricultural or in disturbed urban garden sites the existing and historically intrinsic ecosystem matrices will differ.  As there will usually be a number of remnant matrix variables still interacting on disturbed sites, it will be important for the hemp grower to have a broad understanding of both the intrinsic and existing ecosystem matrices on their cultivation plot or greenhouse.

Knowledge of how the growing plot evolved on a historical basis and how the land functions today will allow the hemp grower to quickly assess trends, those beneficial to desired plant growth and those detrimental to the hemp crop (or any other organically grown crop).

A highly successful Organic Integrated Pest Management System must be based in comprehensive knowledge of how the growing area functioned as an ecosystem in past times and how the farm's present ecosystem variables interact.

With this knowledge the grower can hopefully begin to manage ecosystem matrix variables with organic based approaches.  The finest hemp plants may be grown this way, without toxic and industrial chemicals.  The beauty of organically grown plants encompasses so many health and quality benefits, always appreciated by both the consumer.

How you depict your ecosystem matrix depends on what table, illustration, chart or list works best for you.  Each grower will have their own method.  The important fact is that the grower understands that the cultivation site possesses a historical (intrinsic) set of ecosystem variables which have evolved over time into the unique matrix of today.  

A grower who understands how their intrinsic and existing ecosystem matrices function will produce the very best organic agriculture product with minimal pest pressure.  Organic integrated pest management must begin with this broad understanding of site dynamics.