In plants of the cabbage family, like in other plants, there are pests that show particular activity at certain times of the year. From July to August, female cabbage white butterflies lay a significant number of eggs, from which very appetizing caterpillars hatch, prone to penetrate inside the cabbage and feed on its contents. Folk methods against caterpillars will help if used in advance, after the detection of white butterflies, or if there are still few caterpillars on the cabbage.
Cabbage white butterflies, or cabbage whites, are well known to almost every gardener growing cabbage. There are large and small cabbage whites. Both types of butterflies belong to the Pieridae family. It's difficult to distinguish them if you don't have special knowledge in entomology. The large cabbage white (Pieris brassicae) has coloring from white to light yellow, with two black spots on the wings and black tips. The small cabbage white (Pieris rapae) has a whitish-yellow coloring with a black spot on the wings and black tips. The small cabbage white is more common in gardens, as it is less selective in food than the large one, which prefers cabbage.
This pest winters in the pupal stage on cruciferous plants. In spring, adult individuals begin to lay eggs on the underside of the outer leaves. The eggs hatch in 4-8 days, the larvae undergo a two to three-week development, after which they pupate on the plant. It takes from 3 to 6 weeks from egg to adult. The next adults emerge in a week or two, mating occurs, and eggs are laid for the next generation. There can be from 3 to 5 generations in a year. Cabbage white butterflies actively seek food for their larvae. They can be seen flying in fields and gardens from early spring to late autumn, so some grow cabbage under protective nets throughout the season. However, this does not guarantee protection, as butterflies can find a vulnerable spot and lay eggs inside.
Cabbage white caterpillars are initially green with a delicate yellow stripe on the back and yellow spots on the body's sides. An adult caterpillar has a dark green color with many small black dots, short black hairs, and three yellow stripes. Large cabbage white caterpillars can reach up to 5 cm, small ones up to 3 cm, but both are extremely voracious and capable of completely devouring cabbage, making it hard to remove them from the heads.
To deter cabbage white butterflies, garlic powder and tobacco ash are used. The caterpillars and butterflies do not tolerate the smell of these substances, but after heavy rains or repeated moisture, plants will need frequent dusting again.
Regarding weeds, cabbage whites dislike the smell of tansy but are attracted to the scent of nettle. Therefore, if nettle infusion is used for fertilization, it should be avoided and not used near cabbage. An exception is a trap strip of nasturtium against white butterflies. Regularly watering this part of the garden with nettle infusion will repel most butterflies from cabbage.
A good folk remedy to protect against cabbage whites in July is to use cut tomato stems. At this time, when the tomato bush is forming and pruning of the branches is done, tomato stems can be used for processing even large cabbage beds.
Tomatoes belong to the nightshade plants and contain alkaloids – tomatine and solanine, natural insecticides. To prepare a solution, steep 6 cups of chopped fresh tomato leaves in a three-liter jar of cold water for a day or two. Then filter the liquid and spray it, and use the residues for mulching near cabbage. Fresh tomato stems can be used for mulching, but spraying is more effective. This spray also attracts beneficial insects. Important! Do not use it on other nightshade plants such as eggplants, peppers, or potatoes to avoid spreading diseases. However, it is an excellent solution for cabbage.
Vinegar solution is a well-known remedy against cabbage butterflies, moths, and their caterpillars. To prepare, mix a quarter cup of vinegar with three-quarters water and add a teaspoon of dish soap. This can be used as a spray.
Home insecticides based on vegetable oil with added liquid soap can also be helpful. Mix one and a half teaspoons of liquid soap with a cup of vegetable oil in a liter and a half of water and treat the cabbage, paying special attention to the heads. The oil covers the bodies of insects, suffocating them as it hinders breathing through pores. It is better to use such an insecticide in the evening or morning to avoid damaging the cabbage due to moisture deficiency.
Among commercial biopesticides against cabbage white caterpillars, a product based on Btk (Bacillus thuringiensis kurstaki) can be recommended, which effectively combats this pest, but it needs to be applied every seven days, especially against young caterpillars.
To combat caterpillars on cabbage, agrochemical preparations containing indoxacarb are effective – the dosage and frequency of use are indicated on the label.
In the near future, you can experiment by planting red and purple varieties between white cabbage. In fact, green pests are harder to camouflage on brightly colored plants, making them easy prey for predators. Celery planted next to cabbage can also confuse pests due to its specific scent.
