Caterpillar Control in Hemp and other crops

 Viruses - everyone’s heard more than they want to know about them. Many growers know someone who has dealt with one. But what if we changed the narrative? Not all viruses are harmful.  Gemstar LC is one such example. Gemstar LC is a baculovirus insecticide that contains a naturally occurring virus that infects and kills larvae of the Helicoverpa or Heliothis spp. With this very host-specific virus, beneficial insects, fish, wildlife, livestock, and humans are left untouched while pest species are devastated.

 Originally developed for use on sweet corn, the label has recently expanded to include hemp. Hemp crops can be severely damaged by the following, virus-vulnerable pests:

• Corn Earworm
• Tomato Fruitworm
• Cotton Bollworm
• Tobacco Budworm

 While federally registered for hemp, Gemstar LC is also on many of the state lists approved for use on cannabis.  Gemstar LC can be used late in the crop cycle without residues remaining in the harvested bud.  Gemstar LC can be used the day of bud harvest with just a 4-hour REI.

 Gemstar LC must be eaten by the larvae to be effective. Gemstar LC is most effective against first or second instar larvae, so a scouting program to detect pests very early in the season is recommended. Frequent application at lower rates is more effective than infrequent applications at higher rates, to give larva ample opportunity to consume the virus. Other pesticide products, such as BTs, have a similar mode of action. Combining these products will not increase efficacy, so choosing just one is best.

 Death is not immediate - it may take several days to see results.  Once dead, the insect releases millions of virus particles to potentially infect other insects that come in contact with the cadaver. In summary, this good virus reduces the need for harsh insecticides during a critical part of the crop cycle.

 Some keys to effective results with Gemstar LC

• Label rates are 4-10 oz; use the higher rate for higher insect pressure.

• Gemstar is sensitive to direct sunlight; spraying is best done at times where the sunlight is not as direct like late afternoons, evenings or cloudy days.
• Complete spray coverage is important; typical spray volumes range 20-100 gallons per acre with more required for larger plants.
• Do not use silicone-based spreaders
• Use of methylated seed oils, latex, humic acid even powdered milk have been shown to enhance effectiveness

To learn more about Gemstar LC reach out to your Griffin sales rep or the GGSPro team to find out how a beneficial virus can enhance your insecticide program.

Two Spotted Spider Mite (Tetranychus urticue)

 

Several biological control options for spider mite are available. For preventative measures, species of Amblyseius mites such as A. andersoni, A. californicus, and A. swirskii can be released with sachets that produce vast numbers of mites over a 4-5-week period. This ensures that even if there are no large populations of spider mites on the crop at the time of release, predators will consistently be introduced to prevent populations from developing and establishing. These sachets work by providing a fungal food source for a feeder mite within the sachet. The predatory mites then utilize the feeder mites as their food source. Once the population of predators in the sachet increases, they exit the sachet and begin to look for food on the crop. These predatory mites are great hunters and searchers, giving the grower confidence that spider mites will be found before they become an issue.

For curative measures, there are two options of release. Primarily, Phytoline (Phytoseiulus persimilis) mites are used as the first defense against problematic populations of spider mites. These mites are very particular and will not eat anything except spider mites. This gives the persimilis an edge when wanting to remove outstanding populations of mites, instead of being a preventative method since they cannot survive without spider mites present. These mites are best released via a bottle, blister, or vial depending on the situation. Bottles are typically used in the vegetative state of crop, while vials and blisters are used most typically in the flower state to reduce risk of carrier getting stuck in the flowers. Blisters are a great way to do this because the back of the blister is popped, and then the blister is hung on the crop. The persimilis crawl out themselves and no carrier is spread throughout the crop.

Feltiella can also be used as control measures. These midges lay their eggs in dense populations of mites, with their larvae feeding on mites. They work in conjunction with other bios and can be very effective for establishing control. They are released by trays that are left in the crop, allowing midges to fly and find the sources of food for their larvae.

Though Amblyseius mites are most typically used as preventative measures, they can also be used as a curative. As a curative release, these bios are typically introduced into the crop via bulk material, like a 1L tube or 5L bag, depending on amount needed. Sometimes, broadcast releases over the top of the crop can be a concern to growers, so there has been an increased use of release boxes. Release boxes are small boxes that hang from each plant and are filled manually with the bulk material in the tubes or bags. Once filled and hung, the mites enter the plant canopy the same way that they would from blisters, with no carrier being spread over the crop. Rates of release depend on the density of spider mite populations as well as the density of the plant canopy.

Item Number	Product
SB8042-01	Universal Release Box - Bioline
SB1201-02	P. Persimilis- 2K adult mites
SB0016-03	A. andersoni - 25K adult mites
SB0016-31	A. amdersoni - 200 mini sachets
SB0013-01	A. californicus - 2K adults
SB0013-31	A. californicus - 200 mini sachets
SB1501-01	Feltiline - 250 pupae
SB1201-09	Phytoline Blisters (5)