The hops growing season is consumed with tactical activities like bine training, scouting for pests, maintaining plant health, harvesting cones, and sales. However, managing your hop yard is far from complete once the last cones are separated from the bines. Strategic actions to take now address: after harvest sanitation, soil fertility, drip irrigation, taking a weed inventory, and getting a Pesticide Applicator License.
Sanitation to Reduce Future Pests and Diseases
Postharvest sanitation of the hop yard is your first line of defense against future disease and insect problems.
Leftover refuse from harvest and uncut bines should be removed after the first hard freeze as they harbor fungal spores or live insects. Waiting until after the first hard freeze reduces levels of pests on the debris and reduces spreading problems to unaffected areas.
Collected plant debris with pest infestations can be burned by obtaining an Open Burning Permit from the NJDEP Forest Fire Service. Permit fees are $10 for a 30-day period and need to be signed by your Agricultural Agent certifying the reason for burning is due to disease infection. Forms are available from your agricultural extension office.
Control winter annual and perennial weeds after harvest, as they harbor pests and compete with hops for water and nutrients. Apply a pre-emergent herbicide before winter annual weeds germinate. Perennial weeds translocate carbohydrates to roots and crowns to support the next season’s weed growth. This is an excellent time to apply systemic herbicides to suppress or eliminate these weeds.
No Silver Bullet for Downy Mildew
Downy mildew in NJ, just as in the Pacific Northwest, is the most destructive disease threatening hops. Yield and quality losses from vary depending on varietal sensitivity and timing of infection. Losses range from non-detectable to 100% when significant cone infection or plant death from crown rot occurs. While no single management program assures satisfactory control, careful attention to cultural practices (many little hammers approach) and timely fungicide applications are needed to successfully combat the disease. No hops varieties are immune but varieties do vary in their susceptibility to downy mildew.
Downy mildew flourishes in summer high humidity and temperature conditions. Once established, it remains in the plant and plant debris and is difficult to eradicate. Keeping infection levels low and preventing spread to new bine growth is key. Prevention depends on understanding the disease cycle of Pseudoperonospora humuli; the causal agent of downy mildew in hops and hemp.
Erin Lizotte, Pest Educator at Michigan State University explains, “The pathogen overwinters in buds and crowns or plant debris (infected leaves, stems) left on the field. As shoots emerge in the spring, they may already be infected with this overwintering mycelium. As the hop bine begins to grow, the mycelium produces a microscopic spore-bearing structure (sporangiophore) on the underside of leaves, giving the underside a gray, fuzzy appearance. These structures give rise to an asexual type of spore called zoospores. Zoospores move via wind and rain and act as the major cause of disease spread during the season, infecting new leaves, shoots and eventually even cones. The reproductive cycle that produces zoospores may repeat multiple times over the season, depending on temperature and moisture availability”.
Erin goes on to say, “No data currently exists to suggest that postharvest foliar treatments for downy mildew are beneficial in terms of disease reduction for the next season.” One possibility would be to apply systemic fungicides, yet no research supports their effectiveness. Starting regular preventative sprays after active growth begins in spring are recommended, especially if the disease has been identified in the area, or weather conditions are favorable for disease development.
Leafhoppers, aphids, Japanese beetles, and even European corn borer are observed damaging NJ hops yards. Mites (mainly 2-Spotted Spider mite), while technically not insects, also cause damage. Since leafhoppers do not survive overwinter in NJ most years fall insecticide control is not recommended. Aphids, beetles, and mites may overwinter in our region. However, as with leafhoppers, fall postharvest control is unlikely to reduce populations for the coming season. Aphids and mites overwinter on a variety of nearby hosts of hops yards, including forested areas and shrubs. Beetle grubs overwinter underground, move toward the surface in spring when soil temperatures warm, feed on roots, and later emerge as flying adults that feed on leaves and shoots.
Improve Soil Fertility
Address cultural considerations affecting soils and soil moisture. Though dormant after harvest, hops are living and require soil moisture for satisfactory winter survival. Continue moderate irrigation if soils become dry after harvest, until temperatures reach freezing that prevent irrigation.
Fall is the optimum time for testing soil pH and fertility. Rutgers Soil Test Kits with instructions can be obtained through your local agricultural extension office. Results and recommendations are returned by email. Soil pH in the range of 6.2 to 6.5 is ideal for producing hops. Check the soil pH and make liming applications in fall since pH adjustment may take six months and longer. The active calcium in liming materials is highly immobile in soils; however, fall application provides the time for lime to penetrate the soil.
Get a Pesticide License
If you are new to farming or do not yet have a Private Pesticide License through New Jersey Department of Environmental Protection (NJDEP), the winter months are a good time to obtain it. The license is required if you are using any type of pesticide (general use, organic, or restricted use) on a crop for sale in NJ.