Gram stain of Bacillus thuringiensis under 1000 X magnification. Image credit: Dr. Sahay, Wikimedia Commons
Biological pesticides, or biopesticides, are pest management tools derived from animals, plants, bacteria, and/or naturally occurring minerals. Many common biopesticides uses microorganisms like entomopathogenic bacteria, fungi, nematodes or viruses as their active ingredients. The most widely used microbial pesticides are derived from Bacillus thuringiensis, or Bt. Each strain of this soil bacterium produces a different mix of toxic crystalline proteins; as a result their activity is restricted to certain groups of insects. For example, a relatively new bioinsecticide derived from Bacillus thuringiensis galleriae (Btg), is only toxic to certain beetles, including Japanese beetle adults and larvae!
According to the EPA, biopesticides are generally less toxic than conventional pesticides, often only affect target pests (and closely related organisms), are usually effective at low concentrations and tend to decompose quickly reducing exposures and potentially avoiding the pollution problems associated with conventional pesticides. Biopesticides have long been used as an effective pest management strategy for organic crop production. However, their use has increasingly been recommended as part of Integrated Pest Management programs to reduce the use of conventional pesticides while maintaining high yields.
Biopesticides are coming on the market at breakneck pace; because of this, little is known about their efficacy, particularly on hops. At our hopyard, we are currently evaluating several biofungicides to determine their efficacy at managing downy mildew in hops, and we have been experimenting with bioherbicides for weed management.
As with all pesticide use, carefully follow all label directions to use biopesticides safely and effectively. A note of caution for certified organic growers: even though biopesticides are derived from natural sources does not mean that all are approved for use in organic production. Always check with your certifier before adopting new practices or using new materials.
With temperatures in the 90s this week, keep up the irrigation and be on the lookout for two-spotted spider mites. And remember, keep calm and hop on…
Join us this Thursday, July 23, 2015 from 10 a.m. to 3:30 p.m. for our annual Crops and Soils Field Day at the Borderview Research Farm in Alburgh.
The day will include tour stops to our hopyard where we will discuss critical hop insect and disease pests and our research–including new trials on bio fungicides–to discover effective management strategies for our region.
You will be able to look at hop equipment, including driers, balers, and harvesters. See our trellis and irrigation systems and learn about fertigating. The afternoon will also include a research update on downy mildew and weed management.
“There are three things that matter in property: location, location, location.” We have found that location also matters in growing hops, particularly this spring. Southern Vermont has been exceptionally dry for long periods, while northern parts of our region have been soggy, to say the least.
The cool, wet conditions that we’ve been experiencing in the north typically favor hop aphids, however, we haven’t been seeing many aphids in Vermont hopyards this season. Perhaps they have been slow to move from their alternate host, woody plants in the genus Prunus (cherries, other stone fruits, etc.). Unfortunately, these conditions are quite favorable for downy mildew, so diligent downy mildew management has been a must.
Meanwhile, the relative warmth in southern portions of our region, combined with the early arrival of potato leafhoppers this year, means we are starting to see second generation leafhopper nymphs scuttling across the undersides of hop leaves. This also helps explain the early appearance of two-spotted spider mites as well as spider mite destroyers, their arch nemesis (and our friend). The aptly named spider mite destroyers (ladybugs that specialize on spider mites) can be very helpful when managing spider mites as the season progresses.
The old saying “knee-high by the 4th of July” may be more commonly used when talking about corn, but be on the lookout for our most patriotic of pests: Japanese beetles. Come July 4th, some of us begin to feel like we are knee-high in Japanese beetles.
At this time, our hops in Alburgh are growing quite quickly, up to 15-25 cm a day! During this period of vegetative growth up the strings, it is important to keep up good management practices. Ours include fertilizing, irrigating, weeding, spraying bio-fungicides, and scouting for insects and downy mildew. Our hops are currently being fertilized through the irrigation system–a process known as fertigation. Continuing these tasks is important to ensure that the hops are ready for the switch to their reproductive growth stage, which will begin around June 21st in response to the shortening hours of daylight. Until then, keeping up management practices with the growth of the hops will be keeping us busy.
First, second, and third instar potato leafhopper nymphs.
Adult female potato leafhoppers (Empoasca fabae) arrived to the Borderview research farm in Alburgh between May 23 and May 26. To identify them, stick your hand in a hop plant and ruffle it around–you may see light colored potato leafhoppers fly out. Whether you have seen potato leafhopper yet or not, it is time to start scouting your hop yard for arthropod pests.
The potato leafhopper is a migratory insect pest. The 2014 potato leafhopper population was scarce and did not peak until the end of July. In previous years, potato leafhopper arrived around June 1st and the population peaked earlier (late June to early July) which we can expect in 2015. Our potato leafhopper factsheet has more information on biology and symptoms.
Research we conducted last year showed that 3 adult potato leafhoppers per leaf reduced first year hop photosynthesis. We know this is a pest of concern, but we do not have an economic threshold for this pest on hops. The majority of (organic and non-organic) pesticides labeled for use against potato leafhopper are broad-spectrum products.
Hopperburn: visual V-shaped chlorosis injury caused by potato leafhopper.
Broad-spectrum pesticides not only kill the target pests but also natural enemy arthropods. Therefore, we discourage the use of these broad-spectrum pesticides on hops due to the elevated risk of two-spotted spider mite outbreak. However, we have found that potato leafhoppers prefer to feed on red clover planted in the drive rows than on hop plants. This suggests that planting red clover in drive rows as a “trap crop” may reduce the number of leafhoppers on hop plants. If you give this a try, let us know!
In commercial hop yards, different cultivars are trained on specific dates in the spring. Depending on whether a cultivar matures early, mid-season, or late, there is typically a particular range of days for those plants to start their upward growth. Getting the bines off the ground is also important for managing downy mildew.
Training hops at Borderview Research Farm.
Training dates have not been formally identified for the Northeast region. We trained our hops at the Borderview Research Farm in Alburg this week (Tuesday, 5/26) while some other hop growers reported that they completed their training on 5/19.
We recommend that you make your own observations of hop maturity and write down when you trained each hop cultivar (down the road, we hope to have funds to conduct in-depth research on this important topic).
When training, each string should have 3 or 4 bines. The bines should be trained clockwise as the plants grow towards the sun over the course of each day, winding themselves up the string.
Remember that hop plants can grow 1 foot per day–that’s 6 inches before lunch! Because some varieties mature a little slower than others, our crew will make another sweep around the hop yard to train any later maturing plants in about a week.
At this time of year, it is also critical to irrigate and fertilize. More on that topic coming soon. Until then, stay calm and hop on.
Question: Have we mentioned yet how critical downy mildew management is to the success of our Northeast hopyards?
Answer: Yes, but the importance of managing this disease cannot be overstated–downy mildew can wipe out your crop for the year and even cause hill death in sensitive varieties, so please be on the lookout. Our bulletin, Managing Downy Mildew in Hops in the Northeast, provides some pointers on identifying symptoms and management options.
Yesterday (5/22), our UVM Extension NWCS crew retrieved these “specimens” from our hopyard:
Leaf infected with downy mildew.
Here, we compare a shoot infected with downy mildew (left) with a healthy shoot (right).
Hop N uptake over the season. Oregon State University, 1992. Link to the source article at end of post.
Are your hops already skyrocketing out of the ground? Ours are! While it might seem that there isn’t much to do until the hops are ready for training, it is important to be vigilant in fighting disease.
This week we plan to spray Champ WG copper-based fungicide on our yard as a preventative measure against downy mildew. The disease is now capable of releasing zoospores, which leave from infected tissue and spread to other shoots and plants. Since the plants are small, it is easy to cover the whole plant, reducing the amount of downy mildew spores that are spread, and making life much easier later in the season.
Many fungicides labeled for hops will have an early-season application recommendation. Check your label for that information.
While most nitrogen uptake will happen in June, July, and August, it is still important to supply some early N to your hops so that they can have fertility there when they need it. This week we will apply enough fertilizer to deliver 50lbs of nitrogen per acre. We recommend supplying 75lbs/acre of nitrogen to first-year hops over the course of the season and 150lbs/acre for all subsequent years.
For more detailed guidance on hop fertility, read this great paper from Oregon State on hop nutrient needs: OSU Hop Fertility
Hop downy mildew is currently the biggest pest of concern for Northeastern hop growers. Downy mildew overwinters in the hop crown and primary inoculum will be released from the first shoots. Removal of the first flush of spring hop growth is called “scratching” or “crowning” depending on how far down a plant is cut. Shoot removal is used as an early season preventative measure against downy mildew and as a way of managing harvest time. Hop plants have been budding out for a few weeks now in Vermont.
1st year hop yards should not be crowned to allow for root establishment.
2nd year hop yards should be crowned if downy mildew was a problem last season.
3rd year hop yards should be crowned.
One of the following three methods can be used to kill back the top 1/2-1 inch of each plant.
1. Mechanically cutting (Figures 1 and 2).
2. Flaming. It has been DRY so please be careful not to burn down your hop yard.
3. Herbicide application. Make sure any pesticide used in your hop yard is labeled for use in your state and on hops.
The goal of crowning is to manage disease but also to make vegetative and reproductive growth consistent across the yard and from season to season. In our 2014 crowning date study we found that there was no difference in hop quality or yield between plants cut back on April 14th and May 12th. Hop plants cut back by 5/9 will be able to reach the top of the trellis by June 21 when the plants enter their reproductive growth stage, assuming the plants have sun, water, and nutrients.
Buds before mechanical crowning.
Plant after mechanical crowning.
In this video, Dr. Heather Darby describes what downy mildew is, and some warning signs to look for when evaluating your hop plants.
As part of the Vermont New Farmer Project’s ongoing webinar series, on 4/8/2015, Heather Darby provided an introductory presentation on how to get started with growing hops. Here presentation included establishment considerations, soil fertility, variety selection, pest management, and harvesting tips. The webinar recording is available on our Northwest Crops and Soils Program YouTube channel at: https://youtu.be/SrSoy5wry3w