Before I do that, I want to take a moment to recognize the contributions of Walter Scott, Jr., who served on our Board for more than 40 years and passed away late last month.
Record third quarter sales of $868.8 million increased more than 18% compared to last year.
Sales of $276.5 million grew slightly compared to last year.
Sales of $281.1 million increased 10% year-over-year, led by favorable pricing in all markets and sales growth of more than 25% in wireless communication products and components.
Sales of $96.7 million grew 10% year-over-year, driven by higher pricing, improved general end market demand and sales from our greenfield facility in Pittsburgh.
Global sales of $240.3 million grew more than 72% year-over-year, with sales growth in all regions and higher sales of technology solutions.
In North America, sales grew nearly 55%, as strong market fundamentals and improved net farm income projections continue to positively impact farmer sentiment, generating very strong order flow.
For example, we recently localized some of our electronics assembly in Dubai facility and are increasing the total capacity in our Brazil factory by 50%, positioning us for long-term international market growth, while we continue enhancing service to our dealers and customers.
We are also very pleased that our Irrigation backlog at the end of the third quarter was $388 million, up 26% year-over-year.
Agriculture is quickly becoming its primary economic driver, accounting for 40% of the nation's GDP and employing close to 80% of the local workforce.
We're proud to have initiated this project powering pivots by solar energy, 100% independent from the grid.
Operating income of $80.4 million or 9.3% of sales grew 20% year-over-year, driven by higher volumes in Irrigation and favorable pricing, notably in Engineered Support Structures.
Diluted earnings per share of $2.57 grew 30% compared to last year, primarily driven by higher operating income and a more favorable tax rate of 23.5%, which was realized through the execution of certain tax planning strategies.
On slide eight, in Utility Support Structures, operating income of $24.6 million or 8.9% of sales decreased 170 basis points compared to last year.
In Engineered Support Structures, operating income increased to $34.4 million or 12.2% of sales, a third quarter record.
In the Coatings segment, operating income of $12.5 million or 12.9% of sales decreased 270 basis points year-over-year.
In the Irrigation segment, operating income of $32 million, more than doubled compared to last year, and operating margin of 13.3% of sales improved 270 basis points year-over-year.
Year-to-date, we have delivered operating cash flows of $62 million, with the use of cash this quarter of $8.4 million that reflects higher working capital levels to support strong sales growth.
Year-to-date capital spending of $81 million includes $33 million for strategic growth investments and $55 million of capital was returned to shareholders through dividends and share repurchases, ending the quarter with approximately $170 million of cash.
Based on our recently amended revolving credit facility, our net debt-to-adjusted EBITDA of 1.85 times remains within our desired range of 1.5 to 2.5 times.
We're increasing our earnings expectations for fiscal 2021 by narrowing the earnings per share guidance range to $10.60 to $11.10.
Demand for wireless communication products and components remains very strong, and we are on track to grow sales 15% to 20%, in line with expected market growth.
We now expect sales to grow 50% to 53% this year based on strength in global underlying ag fundamentals and a strong global backlog.
Looking ahead to 2022, strong market demand across our businesses, the strength and flexibility of our global teams and our continued pricing strategies give us confidence in achieving sales growth of 7% to 12%, and earnings-per-share growth of 13% to 15% in line with the three- to five-year growth targets that we have communicated at our Investor Day in May.
The long-term drivers of our businesses remain solid as evidenced by our record global backlog of more than $1.5 billion, up 35% from year-end 2020.

Summary:
Record third quarter sales of $868.8 million increased more than 18% compared to last year.
Diluted earnings per share of $2.57 grew 30% compared to last year, primarily driven by higher operating income and a more favorable tax rate of 23.5%, which was realized through the execution of certain tax planning strategies.
We're increasing our earnings expectations for fiscal 2021 by narrowing the earnings per share guidance range to $10.60 to $11.10.
Looking ahead to 2022, strong market demand across our businesses, the strength and flexibility of our global teams and our continued pricing strategies give us confidence in achieving sales growth of 7% to 12%, and earnings-per-share growth of 13% to 15% in line with the three- to five-year growth targets that we have communicated at our Investor Day in May.