More Strawberries Under Cover: Knitted Fabric Bringing New Promise to Growers

Plant Armor Generation 2 uses two outer polyester layers connected by an inner layer of fine polyester threads, forming a three-dimensional structure with a winding route through the material. Air and water can pass through its pores, but insects face a more complicated journey than they would through an ordinary screen.

A knitted fabric stretched over strawberry plants could give growers more fruit to pick, with a small trial recording more than three times as many berries under the cover. Researchers at North Carolina State University explored this approach in their study, "Knitted 3-D, Porous Textile Cover to Enhance Strawberry Fruit Production and Prevent Insect Feeding," published in Agriculture.

The material, called Plant Armor Generation 2, combines a breathable structure with a physical barrier against insects. Covered plants produced more and heavier strawberries, and laboratory tests showed that young aphids could not pass through the fabric. The outdoor results revealed a practical challenge: protecting a crop requires attention to the plants and openings around the cover, since aphids appeared inside the covered plots too.

A Fabric Designed to Let Water Through and Keep Insects Out

Plant Armor Generation 2 uses two outer polyester layers connected by an inner layer of fine polyester threads, forming a three-dimensional structure with a winding route through the material. Air and water can pass through its pores, but insects face a more complicated journey than they would through an ordinary screen.

Earlier research with the same fabric recorded a 2.93-fold increase in cabbage vegetative growth. The strawberry experiment explored whether those benefits could extend to a crop grown for its fruit. The team planted 24 Sweet Charlie strawberry plants across three raised beds in Raleigh, North Carolina, with four plants in each covered half and four in each uncovered half. Fabric supported by metre-high hoops enclosed the protected plants, and both groups received watering for equal periods as needed. Water applied over the covered plots passed through the textile.

The trial ran through the autumn-to-spring growing season, with harvesting from April to May 2025. No extra fertiliser was added beyond what was already in the growing mixture, and no fungicides were used during the experiment.

More Berries, Heavier Fruit and an Earlier First Picking

Over seven weeks of harvesting, strawberry plants under the knitted cover produced an estimated 3.56 times as many berries as plants grown without it. The covered plants also produced heavier berries, with an average weight of 12.18 grams compared with 6.63 grams for uncovered plants, a difference of about 84%.

The increases in berry numbers and average weight were statistically significant, meaning the results provided evidence that the cover improved the harvest under the conditions tested. For growers, producing more berries and increasing their weight could make the cover useful, though this small experiment cannot show how it would perform on every farm.

Researchers picked the first ripe strawberries from covered plants one week before the uncovered plants were ready for harvesting. An earlier harvest could help growers reach markets sooner and potentially earn better prices, but this pattern needs testing over more growing seasons and in different locations.

The team measured the fresh and dry weight of the leaves, stems and roots after harvesting ended and found no significant difference between the two groups. Covered plants produced more fruit without a measurable increase in the weight of these other parts, and the researchers found no evidence that the plants stretched in response to shade.

Morning and afternoon readings showed that temperatures under the cover averaged 1.93°C higher than in the uncovered plots, offering one possible explanation for the improved harvest. Relative humidity, a measure of moisture in the air, showed no significant difference between the groups, so the cover added warmth without making conditions noticeably more humid.

Those results are relevant to cool-season growing, where a small temperature increase could help fruit development. The trial did not establish how much frost protection the cover provides or prove that it prevents plant diseases.

Aphids Could Not Cross the Fabric in Laboratory Tests

Small aphid populations appeared on both covered and uncovered plants in March, with no obvious difference in infestation levels. Examination of the insects and DNA testing identified them as yellow rose aphids, Rhodobium porosum. Both groups received a single treatment with insecticidal soap to prevent the populations from building up. The outdoor experiment therefore cannot be described as a demonstration of completely pest-free or spray-free production.

To investigate whether the insects could cross the textile, the researchers placed young aphids above the barrier with a strawberry leaf underneath. Each test used 15 aphids and was repeated three times, with observations continuing for three hours. None crossed Plant Armor Generation 2 during the tests. Aphids passed through the ordinary fly screen used for comparison, showing that the knitted material provided a stronger barrier under those laboratory conditions.

The outdoor infestation could have started with aphids or eggs already present on the purchased plants, insects entering beneath the edges, or entry during brief openings for measurements. The study did not establish which route was responsible. For growers, that distinction makes clean planting material and carefully secured edges essential parts of any future use of the cover. A fabric that blocks insects through its surface cannot stop pests already enclosed with the crop.

The Questions That Larger Farm Trials Need to Answer

The researchers examined bacteria in soil attached to the roots to explore whether changes underground might help explain the yield difference. Laboratory-grown bacterial colony counts showed no difference between covered and uncovered plots.

The study tested one strawberry variety in three raised beds at a single location over one growing season, so larger farm trials are needed to see whether growers can expect similar results elsewhere. The fabric lets rainwater through, but its water savings, cost, durability and profitability still need assessment.

The results are promising: covered plants produced more and heavier strawberries, and the fabric blocked aphids in laboratory tests. Aphids still appeared under the covers outdoors, showing that securing the edges and checking plants for pests remain important.