Integrated Pest Management involves using multiple tactics to achieve control at a level that reduces the risk for crop damage, and this process starts with accurate pest identification. For insects, key pests must be identified because not all insects are problems in potatoes. Identifying pests is the first step in creating accurate integrated management programs. There are apps and online resources that can help identify pests as well as diagnostic labs.  

Scouting for key insects provides critical information on both the type and number of pests present. Scouting occurs in predetermined areas within a field where specific life stages and numbers of key insect pests are documented. Threshold levels, when you should take steps to limit economic damage, are used for management, but these levels vary depending on the stage of the insect. Scouting accurately among the whole field for key pests and then using specific thresholds is necessary to ensure proper management. Using new technologies for spatial management and creating maps where insect pests are more prevalent can be valuable if precision application is available and applicable. 

Modes of action, specific active ingredients that have unique activities on the insect or life stage, must be altered and used appropriately in a resistance management program. For some insects like the Colorado potato beetle (CPB), insecticide mode of actions differ in effectiveness by pest life stage. Some insecticides are specific to adults, but others are best for eggs, early-stage instars, or later (3^rd and 4^th instars). Early instar larvae are usually targeted to reduce the first CPB generation in Wisconsin, with a different insecticide mode of action used for next generation management. At times, a third CBP generation can occur in Wisconsin, and if that is the case, an additional mode of action would be needed. At-plant systemic insecticides are sometimes used, but these materials should also be rotated in use to reduce the risk of resistant insects. 

Insect development for overwintering pests can be timed based on degree-day models. Degree days are temperature-based models and can be used to predict when pests may be approaching a specific stage, may be migrating into the state, and/or may cause damage. These predictive tools help time when scouting for specific insect pests should start. To provide accurate information to growers, the University of Wisconsin has the Vegetable Disease and Insect Forecasting Network, which can model specific locations within Wisconsin to determine possible pest prevalence. 

For pests that migrate, such as aphids and leafhoppers, the factors that drive their movement are known and should be considered in scouting and management strategies. Migratory pests usually arrive with warm winds that flow from the south, so tracking those migrations helps growers and scouts interpret patterns of insect progress. Understanding the movement of insects in general is important as well. For example, for potato leafhoppers, when alfalfa is cut, leafhoppers will travel to nearby crops and can cause damage, so if potatoes are near, scouting right after cutting would be advised.  

The key insect pests in Wisconsin potato production can cause catastrophic yield loss if left uncontrolled. Colorado potato beetles will cause complete crop canopy destruction with their direct feeding on foliage, resulting in total yield loss. Potato leafhoppers, with piercing and sucking mouthparts, can cause 20-30% yield loss while also causing tuber maturity and storability problems. Aphids can cause similar damage. Overall, each can cause damage in either the field or with storage, and the crop will not be economically viable without managing these insect pests in the field. 

Insects such as the Colorado potato beetle can develop a tolerance to insecticides and ultimately can become resistant to those materials. Alternating insecticide modes of action between applications, generations, years, and field locations will limit repeated exposure to the same control tools and is a key tenet of resistance management. Using non-chemical control options, such as potato rotation among years and field locations, will also delay resistance development.

One challenging new aspect to consider is the development of metabolic resistance, where insects have developed an inherited ability to overcome general stressors, including new insecticides that they may never have been exposed to. Metabolic resistance has become particularly common for insecticides that are ingested by insects where they are broken down and therefore are not effective. For these materials, multiple control tactics should be used to limit insecticide exposure.   

Plant diseases can significantly reduce potato yield and quality. Diseases can be annual or sporadic, but it is important to remember that diseases can only occur when there is a susceptible host, a virulent pathogen, and a conducive environment, known as the disease triangle. Multiple tactics can help limit disease development, including host resistance, pathogen exclusion, and non-favorable environmental conditions limiting disease impacts.

One key disease in Wisconsin is potato early blight. All potato varieties are susceptible to early blight, and in Wisconsin, the weather accommodates early blight onset, reducing crop photosynthesis and, subsequently, tube production. Integrated potato disease management strategies for early blight include planting tolerant varieties when applicable, emphasizing control tactics in rotational crops, providing good weed management, and maintaining proper fertility and irrigation to ensure plant health. Appropriate disease management and multiple control strategies can be used to protect the vines at their most vulnerable stages.  

Fungicides are used as needed for disease management and to maintain potato plant health. Disease forecasting tools can be used to determine when fungicide use should be initiated. Wisconsin has a robust disease modeling program and has both P-Day (physiological days) and Severity Value calculators that estimate timing for first fungicide applications. These values can be found by looking at data from weather stations around the state or on your own farm and can be used to effectively time applications based on weather data.

For early blight, this forecasting tool predicts when 300 P-days are accumulated, signifying the need to start fungicide applications that are then continued on a regular basis to maintain plant protection. Commonly, broad-spectrum fungicides are used since they will suppress multiple diseases found in potatoes. A comprehensive disease management program will reduce crop yield and quality risks, protect nearby crop fields, and reduce the risk for resistance development. 

Multiple types of fungicides, including preventative, curative, and seed-applied treatments are discussed. Protectants are applied before the onset of disease and are the most effective at protecting plants initially from infections. Curative products may be able to stop or “cure” infections if onset was within a day or two, but longer-term curative fungicide options are rare and therefore need to be used within an overall fungicide management program, which includes the use of both protective and curative materials.

Some of these are broad-spectrum fungicide products, meaning they can control multiple disease pests, while others are single-site or specialty products with specific modes of action and would be designed to control only a certain disease pathogen. Seed-applied materials can be used for certain diseases that are prevalent in Wisconsin, and these are applied during seed cutting to limit seed-borne diseases. Fungicides can also be applied in-furrow at planting to target pathogens in soil or on potato seed tubers. In field applications will usually start around row-closure, based on P-day accumulations, and continue as discussed earlier. Overall, using all fungicide types in a comprehensive disease management program is most effective and reduces the risk for resistance development. 

Fungicide resistance management is aided by the Fungicide Resistance Action Committee (FRAC) codes, a numbering system to describe different biological categories (modes of action) that fungicides act on. Some pathogens are resistant to specific FRAC codes, so these fungicides must be used judiciously and appropriately to delay or avoid resistance. Consideration of FRAC codes can help develop proper fungicide rotations and designate materials with a higher risk of the onset of resistance development to be used only when needed. 

Potato scouting can accurately identify disease development and determine if there are any “hot spots” for disease occurring in the field. Scouts usually travel along field paths made by irrigation equipment, but scouts walk so they can analyze all areas of the field, including by edges of tree lines where applications may not be as effective and therefore, disease may be more prevalent. Also, scouts should know where potato diseases are found on the plant and their key identification characteristics to make accurate diagnoses. 

Late blight is an industry-wide disease problem in potatoes that cannot be allowed to spread but can be managed if proper steps are taken. Potato late blight disease management is required by Wisconsin laws. For example, cull piles must be removed and handled appropriately because they are a source of late blight inoculum. Late blight spores can move up to 40 miles; therefore, inoculum sources need to be eliminated. If late blight is found in a field, it must be managed by crop destruction or through the use of specific fungicides. Blitecast is a tool used to determine risk values for the timing of first fungicide applications for late blight, as it counts disease severity values (DSV) based on weather conditions. When 18 DSVs are accumulated, fungicides should be applied to limit late blight onset.