Drought and Pest Monitoring for Crops: Maps and Alerts

Drought and pest monitoring for crops works best when you combine public maps with your own field checks. In the U.S., the weekly U.S. Drought Monitor rates areas across the country from D0 (abnormally dry) to D4 (exceptional drought), and pest alert networks such as trap surveys and disease maps warn you when a threat is moving into your region. On 29 September 2026, 59.38% of the lower 48 states was in drought (D1 to D4), up from 42.98% a year earlier, according to USDM statistics.

This guide explains how to read the drought maps, which pest alert networks to follow in the U.S., Canada, the UK and Australia, and how to turn an alert into a field visit. It also has three charts built from official data and a calculator to test whether extra monitoring pays on your own acres.

What drought and pest monitoring for crops means

Monitoring means watching for a problem early enough to act. For drought, that means tracking rainfall, soil moisture and plant stress so you can change irrigation, grazing or marketing plans. For pests, it means tracking insect flights, disease reports and crop damage so you scout the right fields at the right time.

There are three layers. The first is regional: public maps and alert networks that cover a county, a state or a whole country. The second is the farm: satellite images, weather stations and soil probes that show which fields are drier or weaker than the rest. The third is the field itself: a person walking the crop, checking leaves, counting insects and digging soil. Each layer answers a different question, and none of them replaces the others.

Drought.gov describes agricultural drought as a shortage of moisture from low rainfall or high heat and wind that dries soils and plants. Its agriculture page notes that monitoring focuses on rainfall, evaporative demand, soil moisture and ground and surface water. Pests are different: the FAO estimates that up to 40 percent of global crop production is lost to pests each year, with plant diseases costing the world economy over $220 billion.

How the U.S. Drought Monitor rates drought

The USDM map is released every Thursday. It has been produced since 1999 by the National Drought Mitigation Center at the University of Nebraska-Lincoln, NOAA and the USDA. Authors from these groups take turns drawing the map, usually for two weeks at a time.

The map is not a single model. Its authors blend rainfall, streamflow, reservoir levels, temperature, evaporative demand, soil moisture and vegetation health with reports of impacts and comments from more than 450 local experts. The USDM calls this a “convergence of evidence” approach. As a rule, the map does not worsen an area by more than one category per week, though it can improve faster after a big storm.

Each category matches a range of percentiles on most indicators. A D2 rating, for example, means conditions that you would expect only 5 to 10% of the time. The USDM drought classification page lists these ranges, along with matching values for the Standardized Precipitation Index.

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How rare each drought category is

Upper end of the example percentile range for most indicators, by USDM category

How much of the U.S. has been in drought

The share of the lower 48 states in drought swings widely from year to year. At the end of September 2012, 65.45% of the area was in drought, the highest end-of-September value from 2012 to 2026. The lowest was 13.82% in 2017. In 2025 the figure was 42.98%, and on 29 September 2026 it was 59.38%, the second highest in that period. These numbers come from the USDM data service, which publishes weekly area statistics for each category.

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Share of the lower 48 states in drought

Percent of CONUS area in D1 to D4 on the last USDM map of September each year

The national share hides big local differences. A county can sit in D3 while the state next door is wet. That is why farm decisions should use the county map, the state drought summary and your own field readings, not the national total. Our Arizona crop drought guide shows how drought stress looks in one dry state.

A drought plan by rating

A plan written before the dry spell is easier to follow than decisions made under stress. The ratings give you natural trigger points. The actions below are examples to adapt with your agronomist or extension adviser; they are not rules from the USDM.

• D0, abnormally dry. Check soil moisture in your main fields. Review irrigation water rights and pump capacity. Note which fields have lighter soils that dry first.
• D1, moderate drought. Look at satellite maps each week for fields that are falling behind. Plan irrigation order. For grazing, look at stocking rates and feed stocks.
• D2, severe drought. Start records for insurance and disaster programs. Talk to your FSA office about LFP if you graze livestock. Consider selling or moving stock before feed costs rise.
• D3 and D4. Focus water on the fields with the best return. Keep dated photos and notes. Watch for pests that thrive on stressed crops, such as spider mites in hot, dry weather, and confirm before you treat.

Signs of drought stress in the field

Maps tell you where to look. These signs tell you what you are seeing when you get there.

• Leaf rolling or curling in the heat of the day, often in corn and other grasses, that does not recover by evening.
• Grey-green or dull colour in leaves, before yellowing or browning starts.
• Uneven patches on sandy knolls, field edges or shallow soils, where water runs out first.
• Poor pollination or small heads when stress hits at flowering.
• Dry soil at depth when you dig or probe in the root zone.

Some of these signs look like pest or disease damage. Root feeders, stem borers and some wilts can also cause wilting or patchy growth. That is why the same weak spot on a map can mean drought in one field and pests in another. Dig, cut stems and look under leaves before you decide.

▶ How satellite crop health maps point you to the parts of a large farm that need a walk. · 4:09

Why the drought rating matters for money

The USDM is not only a map. USDA uses it to trigger some disaster programs. The Farm Service Agency’s Livestock Forage Disaster Program (LFP) pays livestock producers for grazing losses when their county reaches set drought levels during the normal grazing period.

Under the current FSA rules, a county in D2 for at least four weeks in a row qualifies for one monthly payment. D2 for at least seven out of eight weeks in a row gives two payments. D3 at any time gives three. D3 for at least four weeks, or D4 at any time, gives four. D4 for four weeks, not necessarily in a row, gives five. FSA lowered the first trigger from eight weeks to four weeks of D2. Rules change, so check the latest terms with your local FSA office before you plan on a payment.

Not every program uses the USDM. The USDA Risk Management Agency’s Pasture, Rangeland, Forage insurance uses a rainfall index built from NOAA Climate Prediction Center grid data, and RMA says the product is not drought insurance. Growers pick at least two 2-month periods when rain matters most for their forage. Read the policy terms, and talk to a crop insurance agent before you buy.

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LFP monthly payments by county drought rating

Number of monthly Livestock Forage Disaster Program payments for eligible grazing land

Drought monitors outside the U.S.

Other target markets have their own official maps. Use the one that covers your farm.

• Canada. Agriculture and Agri-Food Canada runs the Canadian Drought Monitor. It combines federal, provincial and regional data into one rating on a five-category scale and publishes monthly maps, a drought outlook and historic data.
• North America. The North American Drought Monitor covers Canada, the U.S. and Mexico. It comes out monthly.
• Australia. The Bureau of Meteorology publishes rainfall deficiency and water availability maps rather than a single drought category map.
• UK and Europe. National met services and the EU’s drought observatory publish rainfall and soil moisture anomalies. Check your national service for farm-level advice.

Pest alert networks you can follow

Pest alert networks work like a drought map for insects and diseases. Traps, scouts and labs report what they find, and the network shares it as maps, bulletins or emails. Here are examples by region.

United States and Canada

Crop disease maps. The Crop Protection Network notes that the Corn ipmPIPE tracks where tar spot of corn has been confirmed. Similar county maps exist for other diseases. When a disease appears in nearby counties, it is time to scout your own fields.

Regulatory pest alerts. The North American Plant Protection Organization runs the Phytosanitary Alert System. It posts official reports such as new quarantines from USDA APHIS and new pest finds in Canada. These alerts matter if you ship produce, nursery stock or seed across state or national borders.

Extension trap networks. Many state extension services run moth trap networks for pests such as corn earworm and fall armyworm and post weekly counts in the growing season. Sign up for your state’s crop newsletter to get them.

United Kingdom

The Rothamsted Insect Survey has run two trap networks since 1964. Its suction-trap network has 16 traps, 12 in England and 4 in Scotland. Each trap is 12.2 metres tall and gives daily aphid records in the main flying season from April to November. Growers use the bulletins to time aphid checks in cereals, potatoes and sugar beet.

Australia

State agriculture departments publish pest bulletins in the cropping season. Grain growers in the south-east can subscribe to state pest newsletters that report sightings from agronomists and farmers. Check your state department of primary industries for the one that covers you.

Reading a pest alert: what to do next

An alert is a signal to check, not a signal to spray. A simple routine helps you turn a bulletin into a decision.

1. Check the distance. Is the report in your county, the next county or another state? Closer reports need faster scouting.
2. Check the crop stage. Many pests only cause loss at certain stages. A moth flight after harvest is less of a worry than one at silking or flowering.
3. Scout your own fields. Use the method your extension service recommends, such as sweep nets, leaf counts or sticky traps.
4. Compare with the threshold. Extension guides for major pests give an economic threshold: the pest level at which control costs less than the expected loss.
5. Decide and record. If you treat, follow the product label and local rules. If you do not, set a date to check again.

Weather links the two topics. Hot, dry spells favour some pests, while wet spells favour many leaf diseases. The FAO’s pest study warns that climate change is helping some pests spread to new areas. Watch both drought and pest bulletins together during the season.

▶ What AI pest detection can and cannot do in smart farming. · 6:32

How satellites and drones fit in

Public maps work at county scale. To see which of your fields is affected, you need farm-scale data. Satellites and drones fill that gap.

Satellite images, such as those from the European Sentinel-2 mission, record plant greenness across every field every few days when there is no cloud. A vegetation index like NDVI drops when plants are stressed by drought, pests, disease or poor nutrition. The image shows where the crop is weaker, not why. You still need to walk the spot to find the cause.

Drones give a much closer view of a single field, down to rows and plants. They are useful for checking a weak patch that a satellite has flagged, for counting stand gaps and for crop insurance or damage records. They cost time to fly and process, so many farms use satellites for the wide view and drones or people on foot for the close view. The guide to agriculture technology management covers how these tools fit into one farm system.

Farmonaut Satellite + AI Farm Monitoring System is one example of the satellite layer: you draw your fields once, and it shows vegetation and moisture maps for them through the season. Field managers can also use the agro admin app to track many farms at once.

▶ A step-by-step tutorial on spotting crop stress early with satellite monitoring. · 19:36

How to set up drought and pest monitoring: 6 steps

1. Map your fields. Draw field boundaries and note crop, planting date and irrigation for each one.
2. Subscribe to regional alerts. Bookmark your drought monitor and sign up for state or national pest bulletins for your crops.
3. Set trigger points. Decide in advance what you will do at D1, D2 and D3, and at what trap count or nearby disease report you will scout.
4. Watch your own fields weekly. Check satellite maps, rain gauges and soil probes. Look for fields that change faster than the rest.
5. Scout the weak spots. Walk the areas that the maps flag. Count insects, check leaves and dig for soil moisture.
6. Act and record. Change irrigation, grazing or spraying, and keep records with dates and photos. Records help with insurance and disaster program claims.

Before you spray, confirm the pest, check economic thresholds from your extension service and follow the product label and local rules. The FAO’s guide to integrated pest management stresses using monitoring to decide when, and if, control is needed.

Does extra monitoring pay?

Monitoring costs money: scouting labour, traps, software or drone flights. It pays when it lets you avoid a loss that would cost more. The answer depends on your crop value, how likely a loss is and how much earlier detection really saves. Use the calculator below with your own numbers. The default values are examples set close to break-even, not benchmarks.

Try the numbers for your own farm below.

Drought and pest monitoring tools compared

Common mistakes

• Waiting for D2. D0 and D1 already signal drying. Use them to plan, not just react.
• Treating a satellite map as a diagnosis. A weak zone may be drought, pests, disease, compaction or nutrients. Walk it first.
• Spraying on a regional alert alone. A pest found in the next county is a reason to scout, not a reason to spray.
• Not keeping records. Dated notes and photos make insurance and disaster program claims easier.
• Ignoring soil moisture. Rain totals do not show how much water is left in the root zone. Probe or dig.

Who should use which tools

Small and mid-size farms. Start with the public drought map, one or two pest bulletins and a weekly walk. Add satellite maps when you have more fields than you can walk each week.

Large farms and farm managers. Use satellite maps across all fields, set trigger points per crop and send scouts to flagged zones. Drones help with large weak patches and damage records.

Livestock producers. Track the USDM county rating against LFP triggers, watch pasture growth with satellite maps and plan destocking before feed runs short.

Agtech teams. Developers can pull field data into their own tools; see the satellite and weather API docs.

Related pages on our site: crop loan and insurance support, carbon footprinting, product traceability, fleet management and the Farmonaut app.

FAQ

How often is the U.S. Drought Monitor updated?

Every week. The map is released on Thursdays. The North American Drought Monitor comes out monthly, and the Canadian Drought Monitor also publishes monthly maps.

What does D2 mean on the drought map?

D2 is severe drought. It matches conditions expected only 5 to 10% of the time on most indicators. Four weeks in a row at D2 in the grazing period can trigger an LFP payment for eligible livestock producers.

Can satellites detect pests?

Satellites show where plants are stressed, but not why. A weak zone could be caused by pests, disease, drought or nutrients. Use the map to choose where to scout, then confirm the cause on the ground.

Are drones better than satellites for crop monitoring?

They do different jobs. Satellites cover every field often and at low effort. Drones give a much closer view of one field but take time to fly. Many farms use both.

Where can I get pest alerts for my area?

Start with your state or provincial extension service, the NAPPO Phytosanitary Alert System in North America, the Rothamsted Insect Survey in the UK, or your state primary industries department in Australia.