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An early symptom of HLB in citrus is the yellowing of leaves on an individual limb or in one sector of a tree’s canopy. Leaves that turn yellow from HLB will show an asymmetrical pattern of blotchy yellowing or mottling of the leaf, with patches of green on one side of the leaf and yellow on the other side.

Citrus leaves can turn yellow for many other reasons and often discolor from deficiencies of zinc or other nutrients. However, the pattern of yellowing caused by nutrient deficiencies typically occurs symmetrically (equally on both sides of the midvein), between or along leaf veins.

As the disease progresses, the fruit size becomes smaller, and the juice turns bitter. The fruit may remain partially green, which is why the disease is also called citrus greening. The fruit becomes lopsided, has dark aborted seeds, and tends to drop prematurely.

Chronically infected trees are sparsely foliated with small leaves that point upward, and the trees have extensive twig and limb dieback. Eventually, the tree stops bearing fruit and dies. Fruit and tree health symptoms may not begin to appear for 2 or more years after the bacteria infect a tree.

Huanglongbing has a complex pathosystem (an ecosystem based on parasitism).

There are multiple strains, diverse hosts, several insect vectors, and different environmental conditions that affect the expression and spread of the disease.

Three forms of the disease are known (Asian, African, and American), and these are associated with different species and strains of Liberibactors that are disseminated by different species of citrus psyllid insect vectors. 

The Asian citrus psyllid, Diaphorina citri, is a tiny, mottled brown insect about the size of an aphid. This insect poses a serious threat to California’s citrus trees because it vectors the pathogen that causes huanglongbing disease (HLB).

The Asian citrus psyllid, Diaphorina citri, is a tiny, mottled brown insect about the size of an aphid. This insect poses a serious threat to California’s citrus trees because it vectors the pathogen that causes huanglongbing disease (HLB). This disease is the most serious threat to citrus trees worldwide—including those grown in home gardens and on farms. The psyllid feeds on all varieties of citrus (e.g., oranges, grapefruit, lemons, and mandarins) and several closely related ornamental plants in the family Rutaceae (e.g., calamondin, box orange, Indian curry leaf, and orange jessamine/orange jasmine).

The Asian citrus psyllid (or ACP), damages citrus directly by feeding on newly developed leaves (flush). However, more seriously, the insect is a vector of the bacterium Candidatus Liberibacter asiaticus, associated with the fatal citrus disease HLB, also called citrus greening disease. The psyllid takes the bacteria into its body when it feeds on bacteria-infected plants. The disease spreads when a bacteria-carrying psyllid flies to a healthy plant and injects bacteria into it as it feeds.

HLB can kill a citrus tree in as little as 5 years, and there is no known cure or remedy. All commonly grown citrus varieties are susceptible to the pathogen. The only way to protect trees is to prevent the spread of the HLB pathogen by controlling psyllid populations and destroying any infected trees.

The Asian citrus psyllid is widely distributed throughout Southern California and is becoming more widespread in the Central Valley and further north. The first tree with HLB was found in March 2012 in a home garden in Los Angeles County and a few years later was found in residences in Orange and Riverside Counties. Spread of the disease began to rapidly accelerate in these areas in 2017. Removal of infected trees by the California Department of Food and Agriculture (CDFA) has occurred wherever they have been found.

Huanglongbing (HLB) is a major disease of citrus that has caused catastrophic damage to citrus trees worldwide. The disease causes reduced fruit quality and yield, tree decline, and eventual tree death.

Symptoms are variable and can resemble several disorders of citrus. Typical symptoms include:

• yellow shoots with pale green and yellow flushes;
• non-symmetrical mottled leaves (shades of yellow and green on either side of the mid-rib);
• thickened, leathery leaves;
• enlarged, corky mid-ribs of leaves; and
• leaves with zinc deficiency symptoms that include upright leaves in relation to the shoot (acute shoot-leaf angles).

Defoliation, fruit drop, and shoot dieback occurs in more advanced stages. Young trees may die soon after infection; whereas older trees may die in seven to nine years after infection.

Fruit symptoms include small, misshaped fruit that are lopsided or asymmetrical and exhibit color inversion from yellow to orange to green on the peduncle side while remaining green on the stylar end. The vascular tissue is brownish at the peduncle side of fruit. Seeds of affected fruit are small, brown, and aborted.

Trichoderma harzianum has strong resistance to plant pathogenic microorganisms. After colonization, Trichoderma harzianum can absorb the surplus nutrients in the soil that are not used by the root system.

Trichoderma harzianum has a strong competitiveness to compete for survival resources with diseases, can quickly produce a large number of spores, and has strong fecundity capacity. This type of fungus can produce a large number of enzymes and secondary metabolites that can inhibit plant pathogens.

The chitinase and other substances secreted by Trichoderma harzianum can degrade the cell walls of fungal diseases in soil, allowing the diseases to be preyed on by other soil microorganisms.

In addition, Trichoderma harzianum also has a hyperparasitic effect, which can penetrate the hyphae of pathogenic fungi, absorb nutrients, and kill them. After colonization in the rhizosphere of plants, Trichoderma harzianum forms a physical barrier for the root system, preventing the pathogen from invading the plant.

Cholecalciferol rodenticide has good control effect on Rattus norvegicus, Rattus flavipectus, Mus musculus and other domestic mice. The killing effect was more than 90%.

Rats began to die 48 hours after taking poison bait, and the death peak occurred on the 3rd ~ 5th day.

Cholecalciferol rodenticide

The Brazilian Ministry of Agriculture (MAPA) announced the registration of 22 formulated agri-input products in Act No. 5 published in the Official Gazette of the Union in February. Eight were products with low environmental impact, including those based on biological materials that are harmless to humans and other animals.

Six biological products are based on Beauveria bassiana, Bacillus licheniformis, Bacillus subtilis, Metarhizium anisopliae, Trichoderma harzianum, Trichoderma viride and Spodoptera frugiperda multiple nucleopolyhedrovirus (SfMNPV) which is specific to fall armyworm.

From Agropages

Surfactants are classified by how they split apart into charged atoms or molecules, called ions.

Anionic surfactants have a negative (-) charge. They are most often used with contact pesticides, which control the pest by direct contact instead of being absorbed into it systemically.

Cationic surfactants have a positive (+) charge. Do not use them as stand-alone surfactants often, they are phytotoxic.

Nonionic surfactants have no electrical charge. They are often used with systemic products to help pesticides to penetrate plant cuticles. They are compatible with most pesticide products. A pesticide can behave very differently in the presence of an anionic, cationic, or nonionic surfactant. For this reason, you must follow label directions when choosing one of these additives. Selecting the wrong surfactant can reduce efficacy and damage treated plants or surfaces.

The terms used with pesticide additives can be confusing. People sometimes use the words adjuvant and surfactant interchangeably. However, an adjuvant is ANY substance added to modify properties of a pesticide formulation or finished spray. A surfactant is a specific kind of adjuvant one that affects the interaction of a spray droplet and a treated surface. All surfactants are adjuvants but not all adjuvants are surfactants. For example, drift control additives and safeners are not surfactants.

-Read and follow the label. Is an adjuvant recommended? If so, what type? Do not make substitutions. Some product labels may recommend an adjuvant for one type of use or site but prohibit any kind of adjuvant for another labeled use or site. Suppose, for example, that a certain product is formulated with a wetting agent. If you add another wetting agent when you mix and load a foliar-applied spray, the product may not give better spreading and coverage. Instead, the extra adjuvant may increase runoff, reduce deposition, decrease efficacy and even damage the target plant.

-Use only those adjuvants manufactured for agricultural or horticultural uses. Do not use industrial products or household detergents in pesticide spray mixes.

-No adjuvant is a substitute for good application practices.

-Be skeptical of adjuvant claims such as “improves root uptake” or “keeps spray equipment clean” unless a reliable source can provide research-based evidence to support them. Only use adjuvant products that have been tested and found effective for your intended use.

-Test spray mixes with adjuvants on a small area before proceeding with full-scale use.

Plant-Incorporated-Protectants (PIPs) are pesticidal substances that plants produce from genetic material that has been added to the plant. For example, scientists can take the gene for the Bt pesticidal protein and introduce the gene into the plant’s own genetic material. Then the plant, instead of the Bt bacterium, manufactures the substance that destroys the pest. The protein and its genetic material, but not the plant itself, are regulated by EPA.

Microbial pesticides consist of a microorganism (e.g., a bacterium, fungus, virus or protozoan) as the active ingredient. Microbial pesticides can control many different kinds of pests, although each separate active ingredient is relatively specific for its target pest[s]. For example, there are fungi that control certain weeds and other fungi that kill specific insects.

The most widely used microbial pesticides are subspecies and strains of Bacillus thuringiensis, or Bt. Each strain of this bacterium produces a different mix of proteins and specifically kills one or a few related species of insect larvae. While some Bt ingredients control moth larvae found on plants, other Bt ingredients are specific for larvae of flies and mosquitoes. The target insect species are determined by whether the particular Bt produces a protein that can bind to a larval gut receptor, thereby causing the insect larvae to starve.