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Systems-Level Management

Integrated pest management (IPM) is a pest management strategy formally developed in the 1950s by entomologists and other researchers in response to widespread development in agricultural settings of pesticide resistance in insects and mites, outbreaks of secondary and induced insect and mite pests resulting from pesticide use, and transfer and magnification of pesticides in the environment. Initially focusing on biological control of insects and mites in agricultural systems, IPM has assumed a broader role and meaning over the last 60 years, encompassing management of diseases and weeds as well as insects and mites (and other arthropods) in agricultural, horticultural, and urban settings. Broadly speaking, IPM emphasizes selecting, integrating, and implementing complimentary pest management tactics to maintain pests at economically acceptable levels while minimizing negative ecological and social impacts of pest management activities. Although the details of IPM programs vary to meet the needs of individual cropping situations, all are based on several related principles.

Modern IPM emphasizes the management of agricultural systems, rather than individual pests, to prevent or reduce the number and severity of pest outbreaks. This is also referred to as agro-ecosystem planning or whole-farm planning. A focus on whole-farm planning is also a focus on prevention, which expands management efforts in time and space. In agricultural crops, this includes using cultural methods such as crop rotations and fallow periods, tillage, and variety selection (i.e., use of pest-resistant or tolerant varieties and pest-free rootstock), and legal methods such as quarantines. Included in prevention is the conscious selection of agronomic procedures such as irrigation and fertilizer management that optimize plant production and reduce plant susceptibility to pests. Prevention can be very effective and cost-efficient and presents little or no risk to people or the environment.

Excerpt, Field Guide for Integrated Pest Management in Hops, Third Edition, 2015, James D. Barbour, p. 2.

Pest and Natural Enemy Biology and Life History

An understanding of the biologies and life histories of pests and their natural enemies, as well as an understanding of the environmental conditions affecting their growth and reproduction, provide valuable information for pest management. Knowing which development stage of a particular pest causes damage; knowing when and where the damaging stage of a pest is located within or near the crop; knowing which pest stage is susceptible to particular management tactics; and knowing what host plant(s) and climatic conditions are favorable or unfavorable to pest development—all of these help determine when, where, and how to control the pests of interest. The continuing trend toward more biologically based pest management systems requires detailed information on the life cycles of pests, their natural enemies, unintended consequences of applying certain control measures, and the complex interaction of these factors with the environment.

Excerpt, Field Guide for Integrated Pest Management in Hops, Third Edition, 2015, James D. Barbour, p. 2.

Pests and Diseases

A number of pests and diseases impact hop production. Hop aphids, Phorodon humuli, and Twospotted spider mites, Tetranychus urticae, have long been the two most prevalent arthropod pests of hops. However, several other pests may cause economic injury and must be managed. Detailed descriptions of many of these pests are provided here in the Field Guide for Integrated Pest Management, Third Edition, 2015, Arthropod and Mollusk Management, p. 47.

Both fungal and bacterial diseases may be present, with some exhibiting similar symptoms. Primary fungal diseases include powdery mildew, Podosphaera macularis, and downy mildew, Pseudoperonospora humuli. Verticillium wilt is a potentially damaging disease of hops and numerous other hosts. This disease may be caused by two related fungal species, Verticillium nonalfalfae (formerly V. albo-atrum) and V. dahlia. Detailed descriptions of these and other diseases affecting hops can be found here in the Field Guide for Integrated Pest Management, Third Edition, 2015, Disease Management, p. 12.

Virus and Viroid Diseases

Three carlaviruses are known to infect hop plants: American hop latent virus, Hop latent virus, and Hop mosaic virus. All are known to occur in mixed infections, and all but American hop latent virus are found worldwide. American hop latent virus is found primarily in North America.

Apple mosaic virus is considered the most important virus disease of hops around the world. Originally, it was believed that the disease was caused by either Apple mosaic virus or the closely related virus Prunus necrotic ringspot virus. Recent data indicates that all natural infections of hop are by Apple mosaic virus and that previously described isolates of Prunus necrotic ringspot virus in hop plants were genetic variants of Apple mosaic virus. Infection by Apple mosaic virus reduces the ability to propagate hop plants from cuttings and reduces the success in establishing new hop yards. 

Hop stunt viroid is a sub-viral pathogen that causes a serious disease of cultivated hops. It spread throughout Japan in the 1950s and 1960s. Presence of the viroid in North American-grown hop plants was confirmed in 2004. The disease has been reported in hop-growing regions of Japan, Europe, and North America. Hop stunt viroid can reduce alpha-acids yield by as much as 60% to 80%.

Excerpt, Field Guide for Integrated Pest Management in Hops, Third Edition, 2015, Kenneth C. Eastwell and Dez J. Barbara. Virus and Viroid Diseases, p. 38.

These and other viruses and virus-like disease can have severe impacts on hop quality and yield. Click here for the Nutrient Management section of the Field Guide for Integrated Pest Management in Hops (Third Edition).

Weed Management

Weeds in hop yards can interfere with production by impacting the growth and yield of hops (direct interference) or by interfering with field operations (indirect interference). Weeds compete with hop plants for nutrients, water, and—to a lesser extent—light. (Hops by nature grow tall and are trained to grow on an upright trellis system, therefore competition for light is not the problem it can be with other crops.) Some weeds also provide a favorable environment for certain pathogens or insects, including promoting the survival of detrimental pests during the period when hop plants are not actively growing. A heavy density of weeds in the hop yard can interfere with spraying, training, and harvesting, reducing both the efficacy and efficiency of various practices. Therefore, weed management must be considered in an integrated hop pest management program.

Excerpt, Field Guide for Integrated Pest Management in Hops, Third Edition, 2015, Rick A. Boydston, Bernard H. Zandstra, and Robert Parker. Weed Management, p. 87.

Click here for the Weed Management section of the Field Guide for Integrated Pest Management in Hops (Third Edition).

Nutrient Management

Hop plants produce abundant biomass in the form of bines, leaves, and cones. High-yielding plants such as hops require adequate nutrition. Many of the various nutrients required by hop may be deficient or in excess of the crop’s needs. It can be difficult to pinpoint the cause of abnormal plant symptoms, especially if multiple production factors lead to the same symptom. General symptoms associated with nutrient imbalances are described in this section, as well as known nutrient interactions with diseases and arthropod pests.

Fertilization recommendations vary widely in published literature, differing among production regions, varieties, irrigation methods, soil types, and production goals. Readers should seek input from local experts for guidance appropriate to their region and situation.

Excerpt, Field Guide for Integrated Pest Management in Hops, Third Edition, 2015, David H. Gent, J. Robert Sirrine, and Heather M. Darby. Nutrient Management and Imbalances, p. 98.

 

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