CYD-X® HP is a new aqueous suspension concentrate biological insecticide from Certis USA. It contains a naturally-occurring virus that infects and kills larvae of the codling moth (Cydia pomonella). The scientific name for this virus is Cydia pomonella granulovirus, or CpGV. It is also known as the codling moth granulosis virus.
Granulovirus Mode of Action
Photo: BBA, Darmstadt
Each CpGV particle is naturally microencapsulated within a protein occlusion body (OB) that protects it to some degree from degradation. Each OB measures about 400 x 200 nanometers, meaning 4,000 OB’s placed end to end would span only about 1/16".
A codling moth larva must ingest OB’s in order to become infected with the virus. The highly alkaline environment of the larval digestive tract (where pH can be as high as 10) dissolves the OBs and releases the virus, which penetrates the cells lining the midgut. Once inside, the viral DNA “hijacks” the nucleus of the cell, causing it to replicate numerous copies of the virus which rapidly spread the infection to other organs. Within a few days the infected larva stops feeding, becoming sluggish and discolored as its internal organs fill with virus. Upon death the larva “melts” its fragile outer skin disintegrates to release the liquefied remains of its internal organs, containing billions of new virus OB’s. Each of these is capable of initiation a new infection if ingested by another codling moth larva feeding at that site or wherever OB’s have been deposited by raindrops, gravity, or by spraying CYD-X HP.
Laboratory studies have determined that a dose of 1 or 2 OB’s is all that is required to cause a lethal infection in half of the codling moth larvae tested. A single ounce of CYD-X HP biological insecticide contains nearly one trillion OB’s. Of course, not every OB in a CYD-X HP spray will be ingested by a codling moth larva, but the extremely virulent nature of CpGV toward its host means that it is effective at very low use rates.
Transmission of CpGV
CpGV occurs naturally in codling moth populations, but usually at levels too low to prevent damaging outbreaks in commercial orchards. The virus can persist for years in protected environments such as soil and leaf litter on the orchard floor or in tree cavities. Rainfall, wind, cultivation, movement of animals and birds, and other physical forces can move OBs into areas such as foliage or fruit where they can be ingested by codling moth larvae to begin another cycle of infection. However, the most effective way to initiate CpGV infection is to spray the virus onto the tree in much higher amounts than would otherwise occur naturally.
Once CpGV infection has occurred within a larval generation, there are several ways it can be maintained within the codling moth population. Horizontal transmission occurs when larvae become infected by ingesting virus released into the environment when diseased larvae die. Sometimes infection occurs too late and at too low a dose to kill a larva outright, even though the virus has entered the host cells. A female that survives this sublethal infection may transmit the virus to her offspring, a process known as vertical transmission. In some cases a latent infection can occur, in which the virus lies dormant in the host until stress brought on by overwintering, overcrowding, lack of food, or insecticide exposure causes an outbreak of virus that kills the host. Latent virus can kill host insects even years after initial infection.
CpGV is highly specific to the codling moth. Under artificial conditions in the laboratory, high doses of CpGV can also infect several insect species related to the codling moth, including larvae of the oriental fruit moth (Grapholita molesta). However, the required dose is too high to expect that CpGV products will also control OFM when used against codling moth.
CpGV is noninfectious toward beneficial insects, fish, wildlife, livestock, or humans.
Production and Formulation
CYD-X HP biological insecticide is produced by infecting mass-reared codling moth larvae with CpGV from a “seed stock.” The virus-killed larvae are harvested from the growth medium and homogenized in water to ensure complete release of the OB’s. The resulting suspension is filtered and diluted to its final concentration with water and glycerol, which retards spoilage by microbes that would otherwise grow in the rich “bug soup.”
CYD-X HP contains only CpGV in a homogenate of virus-killed larvae, glycerol, and water. CYD-X HP is listed by both the Organic Materials Review Institute (OMRI) and the National Organic Program (NOP) for use in organic orchards.
Choosing an Application Rate
The label recommended application rate for CYD-X HP is 0.5 to 3 fl.oz. per acre. A rate of 1.5 fl. oz. equates to more than 1 trillion OBs per acre.
CYD-X HP should be applied in sufficient volume of water to obtain thorough coverage of the orchard canopy without excessive runoff, which could carry the virus off the tree. Actual application volume will depend on the type of spray equipment used, but concentrated sprays are usually more effective for applying CYD-X HP than are dilute sprays.
CYD-X HP can be applied at lower label rates (0.5 to 1.0 fl. oz. per acre) if codling moth pressure is low, frequent applications are planned, or if applied in combination with other insecticides also targeting codling moth. Otherwise, higher rates (1.5 to 3.0 fl. oz. per acre) may be required.
Unless used in combination with other insecticides also targeting codling moth, CYD-X HP should be applied at least twice during each larval generation. Multiple sprays at low rates (0.5 to 1.0 fl. oz. per acre) and short intervals are likely to provide better control than a single spray at a higher rate. One economical strategy is to use a higher rate (2 to 3 fl. oz. per acre) for the initial spray to initiate a virus outbreak in the larval population with subsequent sprays at lower rates (0.5 to 1.5 fl. oz. per acre) to maintain the level of infection.
Timing of CYD-X HP Applications
Target Small Larvae
Upon hatching, codling moth larvae wander in search for a spot to penetrate fruit, usually within a day or two after hatching. They may drink water droplets and feed on foliage if no fruit are available. But most don’t eat until after they enter the fruit, and typically do not ingest the skin of the fruit when making an entry hole. Since CpGV must be ingested by the larva to be effective, and may take several days to kill it, optimal use of CYD-X HP requires the virus to be present wherever and whenever small larvae are wandering on foliar or fruit surfaces seeking a penetration site. Virus picked up on the larva’s body and mouthparts will contaminate its feeding site, and infect the larva when it starts to feed. CYD-X HP applications should therefore coincide with egg hatch and this early wandering phase of newly hatched larvae.
When Targeting First Generation
CpGV must replicate within the host larva in order to be effective, so CYD-X HP is slower to kill larvae compared to many chemical insecticides having a toxic mode of action. Virus-infected larvae may still cause superficial “sting” damage where they attempt to enter the fruit, but they usually die before causing the deeper entry wounds that make fruit unacceptable for harvest. Initial CYD-X HP applications can be targeted against the first summer generation of larvae; a low level of early and superficial damage can be tolerated in most orchards and in many cases will be taken care of by thinning. Establishment of CpGV infection in the first generation may also carry over into later generations, making them easier to control with other tactics.
When targeting larvae of the first summer generation (late May to mid-June), make the first application of CYD-X HP at the beginning of egg hatch, or shortly thereafter. If using a degree day model to predict codling moth development, then the first CYD-X HP application should be around 250 degree days after codling moth biofix, assuming a base temperature of 50° F. Make a second application after 7 sunny days (two cloudy days should be counted as 1 sunny day). Third and fourth applications may be required under conditions of unusually high codling moth pressure, sustained egg laying, or prolonged sunny weather. If you can only make two applications, it may be more effective to hold the second spray until peak egg hatch.
Second and Later Generations
The second summer generation of larvae can cause more severe damage directly to fruit intended for harvest. Although CYD-X HP will infect and kill many of these larvae, it will not prevent them from damaging the fruit before they die. Unless the orchard is certified organic, or codling moth pressure is already low, in most cases it is better to rely on fast-acting chemical insecticides to prevent damage to fruit. CYD-X HP can still be included in a chemical spray program against second and later larval generations to combat resistance and reduce overwintering success. Codling moth larvae resistant to chemical insecticides are still susceptible to the virus.
If using a degree day model to predict codling moth development, CYD-X HP applications directed against the second generation should begin by about 1200 degree days after codling moth biofix, just before predicted egg hatch. Depending on weather and location, it may be more convenient to simply continue spraying lower rates of CYD-X HP at regular intervals of 7 -14 days from the end of the first generation through the beginning of the second.
First generation CYD-X HP applications should correspond roughly with first and second cover sprays, second generation with fourth and fifth cover sprays. However, weather conditions, local topography, quality of monitoring, and other factors influence how accurately degree day models can predict actual codling moth development in any given orchard. Consult your University Cooperative Extension Service, crop consultant, or other local pest management professional for information on monitoring of codling moth in your orchards.
Using CYD-X HP With Pheromone Mating Disruption
CYD-X HP can be used in combination with codling moth mating disruption as a means of overall population management. CYD-X HP can be used to prevent establishment of larval infestations by immigration of codling moths from bordering nondisrupted or abandoned orchards, or to treat areas unsuitable for mating disruption due to size, shape, slope, wind, or other factors.
Storage and Handling
For best results, CYD-X HP should be refrigerated when not in use. Bioactivity of the virus can be degraded by exposure to high temperatures ( > 90°F) for long periods. Always store CYD-X HP in its original bottle in a cool, dry place, out of direct sunlight. Shake well before use. CYD-X HP can also be frozen for extended storage without harm.
Water used for mixing the spray should be at or near neutral pH (7) before adding CYD-X HP. Highly alkaline conditions (pH > 9) will prematurely degrade the protein occlusion body, reducing bioactivity and stability of the virus. Buffer the water in the spray tank if pH is above 9 or below 5, or if it contains materials such as lime sulfur or foliar fertilizers that may create pH extremes.
Spray CYD-X HP as soon as possible after mixing. Do not delay more than a few hours between mixing and spraying, especially if pH is not neutral.
Use of Spray Adjuvants
Because of the way it is made, CYD-X HP contains natural compounds derived from host larvae that can provide some protection from the UV rays in sunlight. Additional protection, as well as enhanced spray deposition and rainfastness, may be obtained by using certain adjuvants with CYD-X HP. Pinolene or related stickers, latex, methylated seed oils, humic acid, and powdered skim milk have been used with some degree of success, but Certis USA cannot guarantee performance of any adjuvant from another company.
Refer to the adjuvant label or see your dealer for more information on a specific adjuvant.
In many cases, performance of CYD-X HP is more likely to be improved by addition of a feeding stimulant such as sugar or molasses (which also acts as a sunscreen) at a rate of 5 pounds per acre. Larvae will then ingest virus more quickly as they feed preferentially on spray droplets, reducing the time of exposure of the virus to sunlight and increasing the rate of infection.
Exposure to sunlight can be reduced and effectiveness of the virus increased by spraying CYD-X HP in the late afternoon or early evening. Avoid spraying in intense sunlight.
Want to know more about Insecticidal Viruses?
Click here for Insecticidal Viruses 101.