Plant disease expert cultivates elite microbial strains: Bacillus subtilis makes strawberries plump and bright red, no gibberellin needed, and even less pesticide

Arriving at farmer Wu Shengbao's strawberry field in Dahu, Miaoli, under the lush, deep-green leaves hang one plump, glistening bright red fruit after another, a thriving scene across the whole field that astonishes the eye. It turns out that halving pesticide use is no dream; even the most delicate and hard-to-manage strawberries can achieve it, and the plants are even more productive and healthy!

Behind the beaming farmer is a master's guidance. The teacher who guided Wu Shengbao to halve pesticide use and make good use of beneficial microorganisms is Zeng Deci, a retired professor from the Department of Plant Pathology at National Chung Hsing University. Zeng Deci has long advocated for a plant doctor system and has developed microbial formulations; this time, in cooperation with the Agricultural Technology Research Institute, he has mentored farmers growing various crops in trials, with remarkable results.

"I've grown strawberries for over twenty years, and this is the year that saved the most time and effort," the farmer said. In the past, pesticide dealers would mix up a lot of pesticides, but now with the teacher's guidance, most of the chemicals are saved. "So I very much support plant doctors: whatever the disease, prescribe the right medicine, treat the root cause!"

Large fruit makes up as much as 75%, with no gibberellin used at all

The whole of Dahu is covered in strawberry fields, yet Wu Shengbao's field stands out. Most strawberry fields suffer from missing plants, some at rates as high as 50% to 60%, looking sparse at a glance. Otherwise, leaves yellow, grow thin and flop limply, repeatedly hit by anthracnose and Fusarium; among insect pests, the two-spotted spider mite, commonly known as "red spider," is also rampant.

Yet in Wu Shengbao's strawberry field, the greenery is especially deep and rich, with no missing plants at all, and the leaves are extremely numerous, each one quite thick and firm. Looking closer at the strawberry fruit, large fruit makes up as much as 75%, better than in previous years, with no gibberellin used at all, and the texture is firm, not hollow. Not only has overall yield risen by 20% to 30%, the flavor is also better, delighting the couple as they pick.

Disease- and pest-resistant, with no missing plants; the plants are strong and productive

Wu Shengbao was already a farmer who used pesticides precisely, with low chemical pesticide use, and now has cut it by more than 50%. He explained in detail that in the two months after planting, disease prevention is needed; previously he sprayed about once every 10 days, but now it is extended to 20 days. Then comes the harvest period, when spraying frequency is even lower; originally red spider mites were controlled about once a month, but now the interval has also lengthened, with only three sprays from planting to now, over four months.

Zeng Deci pointed at the strawberry leaves with satisfaction and said, "Red spider mites don't like to eat healthy leaves." This great enemy of strawberries is almost nowhere to be seen in Wu Shengbao's field. "When leaves are thick, they withstand stress, and when plants are healthy, the fruit is plump and firm with natural flavor." Anthracnose and Fusarium are also almost extinct.

Disease- and pest-resistant, with no missing plants; the plants are stronger and more productive. How exactly is it done?

It turns out that the secret weapon Zeng Deci mentored the farmers to use is the "Bacillus subtilis functional nutrient formula." Wu Shengbao said there are two methods: foliar spraying and applying with irrigation water to the soil, working together. "Spray on top once every 3-4 days, and apply below once every 7-10 days." In this way, not only is pesticide use cut by more than 50%, but fertilizer is also saved by 40% to 50%.

Elite microbial strains from a guava orchard in Wufeng

"Bacillus subtilis is naturally widespread in nature," said Zeng Deci, an authority on plant pathology. In the past, when isolating pathogens, he found that wherever Bacillus subtilis was present, pathogens could not grow, which led him to research Bacillus subtilis.

He isolated and screened strains from the rhizosphere and growing media of various crops in various places. For example, this strain named "WG6-14": W stands for from Wufeng, and G stands for from guava (Guava), meaning it is a Bacillus subtilis strain screened from a guava orchard in Wufeng.

A common problem with microbial formulations is that they show little effect after spraying, or are hard to preserve, with a short shelf life, dying at the slightest temperature change. However, Zeng Deci screened out the strongest strain, which not only has obvious effects but can also be stored for one year at a low temperature below 10°C.

How do you cultivate the strongest soldiers? Zeng Deci explained that the primary screening criterion is the ability to form "endospores." "First boil it in 100°C hot water for five minutes; whatever survives is spores." When Bacillus subtilis is in the endospore state, its ability to resist stress is especially strong. "Spores can sleep and get through harsh environments."

After being tested by high heat, it of course must also be able to resist pathogens: "wherever it grows, pathogens dare not come near." In addition, it is best if it can also promote plant root growth, which depends on the metabolic substances of Bacillus subtilis.

Use the best nutrient packets to raise the best soldiers

Raising soldiers requires provisions, so the nutrients and environmental conditions for culturing the strains are extremely important. The nutrient formula, suitable temperature, and whether aeration is sufficient all affect the quality of Bacillus subtilis. The strain must also be pure enough, with no contaminating microbes. The Bacillus subtilis screened by Zeng Deci reaches a concentration of 100 billion per 1 c.c.; when transferred to a petri dish to multiply, almost no contaminating microbes can be seen.

Besides exerting an antagonistic effect against harmful microbes, these beneficial microorganisms can also "bring a lunchbox" to the crops. Zeng Deci explained that culturing beneficial bacteria involves giving different nutrients, such as fish meal, soybean meal, and brown sugar; after the beneficial bacteria decompose and transform them, crops can absorb them more easily. The metabolic substances produced by the beneficial bacteria have the effect of resisting pathogens and promoting plant growth.

"Use the best nutrient packets to raise the best soldiers." Zeng Deci explained that this nutrient can be adjusted according to the nutrients a crop especially needs at different stages: when more nitrogen fertilizer is needed, use nutrients with high nitrogen content to culture the bacteria; at the flowering stage, more phosphorus components are needed; when the fruit is about to ripen, use more potassium components.

In Wu Shengbao's work shed is a large fermentation tank specially designed to culture the strains. After putting in the nutrients and strains, it is heated to the optimal temperature and continuously stirred at a constant temperature for seven days, allowing the strains to fully decompose and transform the nutrients; this is "enriched culture." Zeng Deci explained, "When spores meet heat, with water and nutrients, they wake up and begin to decompose the nutrients; once decomposed, the plants absorb them more easily. The strains also secrete metabolites, such as phenolic acids, which are very good for the root system."

Farmer: Climate change brings endless new problems, and pesticides are not enough to cope

Another cooperating farmer in Dahu, Zhang Meidan, grows elevated strawberries. "I have been moving toward a non-toxic approach; at a height like elevated strawberries, when you spray, you're breathing it in yourself."

Zhang Meidan began using Bacillus subtilis nutrient solution last year. After harvesting began in December, she stopped using chemical pesticides and sprayed Bacillus subtilis once every five days. "This year not only are there fewer diseases, but the best result is with the two-spotted spider mite. Previously I had to spray once a month, and each time it cost three to four thousand yuan in pesticide; this year, from beginning to end, I sprayed only once."

Zhang Meidan and Wu Shengbao also mentioned that strawberry farmers are often troubled by buying diseased seedlings, yet they may not have the ability or time to raise seedlings themselves; at such times, Bacillus subtilis nutrient solution can also help. Whether raising seedlings yourself or buying seedlings, before planting, soak the roots in Bacillus subtilis nutrient solution to bring the beneficial bacteria into the soil, and in the future they will grow strong and sturdy.

Wu Shengbao said that with drastic climate change now, new problems emerge every year, even giving experienced farmers headaches. For example, in recent years the Toyonoka variety has become harder and harder to grow, and many people have switched to the Xiangshui variety, which can resist powdery mildew; but once this variety encounters anthracnose and Fusarium, "it dies within a few days, catching farmers off guard, whereas Toyonoka could at least hold out for half a month."

Wu Shengbao gave an example: the "big and small ears" caused by Fusarium. Strawberries grow three leaves together, and after infection one or two of the three leaves become