Summary of How Brix Levels Impact Insect Pressure on Plants | Dr. Thomas Dykstra

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00:00:00 - 01:00:00

In this section of the webinar, Dr. Thomas Dykstra introduces the concept of leaf Brix readings and their impact on insect feeding on plants. He emphasizes that insects are not competing with humans for food and gives examples of insects that feed on nutritionally poor or decaying materials. Dr. Dykstra discusses the need for a more scientific approach to determine the healthiness of a plant and introduces the concept of using refractometers to measure Brix levels. He explains that Brix levels can impact insect pressure on plants and discusses the digestive systems of aphids and other insects. Furthermore, he highlights the importance of protein folding in insect digestion and the significance of sugar production in plants. Dr. Dykstra also discusses the impact of pesticides and high salt fertilizers on plant health and the microbial ecosystem in the soil. Finally, he explains how different factors like no-till practices, UV deficiencies in greenhouses, and glyphosate herbicide can affect insect pressure on plants. The section concludes with a preview of the next presentation, which will focus on the specific insects affecting citrus crops in the Florida orange industry.

00:00:00 In this section of the webinar, Dr. Thomas Dykstra introduces the topic of leaf Brix readings and their impact on insect feeding on plants. He explains that insect herbivory occurs when insects feed on plants that are considered nutritionally poor, dead, or dying. Dr. Dykstra emphasizes that insects are not competing with humans for food, using examples like elephant dung beetles and termites that feed on materials humans wouldn't consume. He sets the stage for a presentation that will delve into the concept of leaf Brix levels and their relationship with insect herbivory.
00:05:00 In this section, the speaker discusses various insects that do not compete with humans for food. Love bugs, for example, feed on decaying vegetation, which is not the type of food humans prefer to eat. Similarly, clothes moths, beetles, and flies feed on decaying materials or carrion, which are not part of human diets. Cockroaches scrounge for food scraps behind refrigerators but are not a food source for humans. Fruit flies specifically target overripe fruit, which humans tend to avoid. Stored product insects only attack food after it begins to deteriorate in storage. Overall, the speaker emphasizes that these insects pose no competition for humans when it comes to food consumption.
00:10:00 In this section, Dr. Thomas Dykstra discusses how insects are not competing with humans but instead only go after bad food and nutritionally poor, dead, or dying plants. He supports his point by highlighting that insects in the tropical rainforest are very selective and only feed on certain plants, leaving most of the vegetation untouched. He then explores the question of what constitutes a healthy plant and mentions that factors like height or fast growth cannot be used as indicators across all plants. Therefore, determining the healthiness of a plant requires a more scientific approach, especially when insects are not present to provide indicators.
00:15:00 In this section, Dr. Thomas Dykstra discusses various indicators of plant health and why they may not be reliable. He mentions that factors such as rapid growth, green color, flowering, and even root systems cannot be solely relied upon as indicators of plant health. Instead, he suggests using a refractometer to test plant sap, specifically measuring the level of sugar or bricks. Dr. Dykstra explains that a refractometer provides a fast and reliable way to determine plant health within a matter of minutes. He also mentions that there are different types of refractometers, including handheld and digital ones, with the latter being preferable for those who want to have more precise measurements. Ultimately, using a refractometer to measure bricks levels can provide a clearer understanding of a plant's overall health.
00:20:00 In this section, Dr. Thomas Dykstra discusses how Brix levels can impact insect pressure on plants. He explains that while a Brix level above 12 is generally considered healthy for plants, it is not the only factor to consider. Different types of insects, such as grasshoppers and aphids, eat plants for different reasons and cannot be assessed using the same scale. Dr. Dykstra also explains how the digestive system of aphids is different from other insects. They have a unidirectional system that allows nutrients to be absorbed directly into the hindgut, resulting in the excretion of mostly sugar. If aphids consume too much sugar, it can overwhelm their system and quickly kill them. Additionally, Dr. Dykstra discusses how enzymes can partially digest proteins, leading to incomplete proteins that may require specific co-factors to be fully broken down.
00:25:00 In this section, Dr. Thomas Dykstra discusses the importance of protein folding in insect digestion and how it impacts their ability to break down complex molecules. He explains that proteins need to fold correctly in order to function properly, and the folding process is influenced by factors like disulfide bridges and cofactors like zinc. He also mentions that insects prefer dissolved nutrients, similar to how humans receive nutrients through IV fluids, and explains the different levels of sugar molecules that insects can digest. He highlights that cellulose, a polysaccharide found in trees, cannot be digested by humans due to the specific bond it contains. Overall, this section emphasizes the intricacies of insect digestion and the limitations of human digestion.
00:30:00 In this section, Dr. Thomas Dykstra explains the significance of sugar production in plants and how it affects their overall health. He emphasizes that a healthy plant needs to take care of itself both above and below the soil, as well as support the microbes in the soil. He introduces the concept of Brix levels, which indirectly measure the rate of photosynthesis by measuring the sugar content in plants. Dr. Dykstra provides a leaf Brix chart with different levels ranging from 1 to 20, focusing on the leaf rather than fruiting structures. He discusses the importance of maintaining Brix levels between 3 to 7, which represents the majority of crops. Plants in this range have a fighting chance but may require occasional force feeding to stay relatively healthy. Additionally, Dr. Dykstra mentions that around 6 Brix, plant secondary metabolites increase, contributing to color, flavor, taste, and smell in the plant.
00:35:00 In this section, Dr. Thomas Dykstra explains how the Brix levels of plants impact insect pressure. He mentions that plant secondary metabolites start to increase at a Brix level of six, meaning anything below that is relatively tasteless. The highest Brix level tomato he has encountered at a store is 5.2, which explains why many store-bought tomatoes lack flavor. As the Brix levels increase from seven, eight, and higher, the plant becomes more resistant to insects. When the Brix level reaches 12 and above, the plant is considered objectively healthy and free from insects and disease. Dr. Dykstra emphasizes that plants need sunshine, water, air, and nutrients to attain high Brix levels. Factors such as low light levels, water imbalance, lack of air, and nutrient deficiencies can contribute to lower leaf Brix levels. Additionally, the use of pesticides, including insecticides, fungicides, and herbicides, can reduce leaf Brix levels by killing beneficial microbes.
00:40:00 In this section, Dr. Thomas Dykstra discusses how the use of pesticides and high salt fertilizers can negatively impact the microbial ecosystem in the soil and ultimately affect plant health. He explains that herbicides, fungicides, and insecticides are designed to target specific types of microbes, but in doing so, they can compromise the overall microbial balance. He also mentions that high salt fertilizers can stress plants and make them dependent on these fertilizers, rather than obtaining nutrients in a natural way. Additionally, Dr. Dykstra mentions that GMO plants often have lower Brix levels and are more prone to insect infestation. Strict no-till practices, like those in citrus farming, are recommended to preserve root systems.
00:45:00 In this section, Dr. Thomas Dykstra discusses how different factors can impact insect pressure on plants. He mentions that strict no-till practices can contribute to issues, especially in citrus groves, as pesticides can kill beneficial microbes that help keep nutrients in the soil. He emphasizes the importance of nutrients like calcium and explains that heavy atoms, such as calcium, can fall due to gravity if not kept in the proper zone by microbes. Greenhouse plants, on the other hand, face UV deficiencies because glass and plastics used in greenhouses are effective at absorbing UV. Dykstra explains that UV is fundamental to plant health and that plants will try to find ways to reach UV, even if it means growing towards openings in the greenhouse roof. He also highlights the role of certain amino acid residues in absorbing UV radiation.
00:50:00 In this section, Dr. Thomas Dykstra explains how different brix levels impact insect pressure on plants. He discusses how glyphosate, a herbicide, affects the synthesis of essential amino acids in plants and how compromising plant health can make it difficult for insects to survive. He categorizes insects into different groups based on their preference for specific brix levels. Grasshoppers are the toughest and can tolerate higher brix levels, while chewing insects lose interest when the brix level reaches 9 to 11. Sucking insects, like leafhoppers and stink bugs, lose interest when the brix level is between 7 and 9. The aphid group, including aphids and scale insects, loses interest when the brix level is between 6 and 8. Dr. Dykstra explains that plants with lower brix levels are more likely to attract aphids, and by increasing the brix level of a plant, aphids can be killed relatively quickly. He also mentions that even in the middle of feeding, if a plant increases its brix level, chewing insects like fall webworms can lose interest and eventually starve to death. This demonstrates the sensitivity of insects to brix levels and how they can impact insect pressure on plants.
00:55:00 In this section, the speaker discusses how the next presentation will focus specifically on the citrus industry, particularly Florida oranges. He explains that growers have inadvertently invited pests into their groves as they lower the bricks levels. The upcoming presentation will dive into the specific insects that are affecting citrus crops and explain how each one is being selected as the bricks levels decrease. While this current presentation provided a general background, the next one will offer more specific details for those interested. The section concludes as the speaker thanks the audience for their time and invites them to return for more specific information in the future.

01:00:00 - 01:25:00

Dr. Thomas Dykstra discusses the impact of Brix levels on insect pressure on plants. He explains that different groups of insects can indicate the health of a plant and suggests that assessing Brix levels can help manage and prevent insect pressure. He also addresses specific scenarios such as the use of toxic sprays, the impact on fruit health, resistance to grasshoppers, and terminating cover crops. Additionally, he discusses the importance of mitigating UV radiation and monitoring the plant's conductivity levels during the transition from vegetative to reproductive stages. Dr. Dykstra provides valuable insight into understanding and utilizing Brix levels to protect plants from insect attacks.

01:00:00 In this section, Dr. Thomas Dykstra discusses the impact of Brix levels on insect pressure on plants. He explains that different groups of insects can indicate the health of a plant. For example, if grasshoppers are not interested in eating low-level plants, it suggests that the plants are healthy. On the other hand, if a grasshopper bites a plant and stays to feed, it could indicate that the plant's health is compromised. Dr. Dykstra also addresses the use of toxic sprays to handle gypsy moths, noting that healthy trees are typically not targeted by these moths. He suggests that instead of spraying, it's important to consider the health of the tree and assess its Brix levels before taking any action. Another question he addresses is regarding katie dids, which are pests that eat fruit. He suggests that Brix levels can be a good indicator of the health of the fruiting part of the plant, but it's not the only factor to consider. Overall, Dr. Dykstra emphasizes the importance of understanding Brix levels to manage and prevent insect pressure on plants.
01:05:00 In this section, Dr. Thomas Dykstra discusses the impact of Brix levels on insect pressure on plants. He explains that while Brix readings can give an indication of plant health, it cannot be used as a measurement of fruit health once the fruit begins maturing. This is because as the fruit matures, sugars are pushed into the fruit by plant genetics, resulting in a high Brix reading even if the fruit is not resistant to insects. However, measuring the Brix reading of a green fruit before sugars are pushed in can provide some correlation to leaf values. Dr. Dykstra also mentions the problem of invasive species like the spotted lanternfly and the emerald ash borer, stating that plants must be brought down to a certain level before they become attractive to these insects. He emphasizes that the principles discussed apply universally to all insects, regardless of the specific species.
01:10:00 In this section, Dr. Thomas Dykstra discusses the concept of plants becoming resistant to grasshoppers. He mentions that in African countries, grasshoppers can selectively decimate crops, indicating that there are certain plants that grasshoppers are not interested in. He uses the example of the tropical rainforest, where there are many different plant species that grasshoppers do not feed upon. This suggests that many crops can develop resistance to grasshoppers. Once plants are resistant to grasshoppers, they are likely to be resistant to other pests as well. However, Dr. Dykstra also points out that if crops become healthier and more nutritious, other pests like crows and deer may become more interested in them. He acknowledges that this goes beyond his expertise as an entomologist. Additionally, when it comes to terminating cover crops, Dr. Dykstra advises against using herbicides, as they kill everything and waste away nutrients. Instead, he suggests working the cover crops into the soil, allowing microbes to digest them and utilize their nutrients.
01:15:00 In this section, Dr. Thomas Dykstra discusses the impact of Brix levels on insect pressure on plants. He explains that working cover crops back into the soil can help bring nutrition back without being burned off by the sun. However, he acknowledges that this might not be possible in certain situations, such as citrus crops. He also mentions the importance of mitigating ultraviolet (UV) radiation in high tunnel and greenhouse environments, recommending opening the roof or using UV lights to counteract the nutrient loss caused by lack of sunshine. Dykstra emphasizes the importance of moving plants out of the greenhouse as soon as possible to prevent insect infestations, as continuous greenhouse growth attracts specific insects. He also notes that phylloxeridae, a type of sucking insect, tends to have low Brix levels.
01:20:00 In this section, Dr. Thomas Dykstra explains that the switch from the vegetative stage to the reproductive stage in plants can cause physiological changes that stress the plant and make it more susceptible to insect attacks. He suggests that low electrical conductivity in the soil could contribute to this stress, and if the plant is unable to handle the reproductive stage well, it may attract caterpillars. Dr. Dykstra advises monitoring the plant's conductivity levels and flower count to assess its health and potential vulnerability to insect pressure. He emphasizes that the transition from vegetative to reproductive stages is a stressful process for plants and recommends paying attention to these factors to prevent flowers from being attacked by caterpillars.
01:25:00 In this section, Dr. Thomas Dykstra mentions that he has written several blog posts on how to measure brix levels at different times of the day and in different locations on the plant. He encourages viewers to visit his blog and refer to the index to find these posts. He also thanks Tom for sharing the information and looks forward to the next webinar.