Caraway: Pests, Diseases and Their Control

2015

Caraway pertains to aromatic plants grown for years in relatively large areas and its field production is often concentrated within specific particular regions. Under such circumstances this crop is more frequently attacked by pests and diseases than other medicinal plants. Pests are the major threat to caraway, especially if not controlled, they can cause a total loss of fruit yield.

Deppresaria nervosa Hav. appears to be the most serious pest. Adults overwinter under tree bark, in straw left in the field, in sheds etc. In the second year of caraway vegetation the females deposit eggs into leaf folds. An emerged caterpillar, which first is of light then dark-grey colour with a visible row of black mamillae with a white border, finally turns black. Initially, caterpillars feed on the leaves, then as the plant grows, they get into umbels covering them with web, destroying the flowers and newly formed fruits. When their feeding is over, at the beginning of fruit ripening, caterpillars move down the plant and gnaw into the stem for pupation. More than ten pupae may be found within a single stem. Adults appear after 3–4 weeks in July and some time later they seek for overwintering shelters (). This is a common pest, especially in the regions of caraway intensive cultivation. Its mass appearance could be avoided by an adequate crop rotation with a limited participation of caraway. However, protection against this pest is mainly based on chemical control. The main spraying should be performed in spring of the second growing season, upon monitoring conducted over the initial period of adults’ appearance. During their mass flight the treatment should be repeated at least 3–4 days prior to flowering. If the pest is abundant during flowering, its chemical control can be carried out only in the evenings for bee prevention. At initial infestation by young larvae, caraway can be treated with biological formulations (e.g. Dipel 3.2 WP, Bactospeine PM 6000, Bacilan). Chemical control against this species, as against other pests and diseases, should be conducted upon the actual recommendations established in particular countries.

Another serious pest of caraway crop is Aceria carvi Nal., invisible by the naked eye. Adult mites overwinter within caraway leaf rosettes and in March they start feeding. In April the females deposit eggs on the surface of leaf blades or at their base. The nymphs which hatch from eggs, after two weeks transform into adults. Several generations may develop during the growing season. In September the mites move towards overwintering shelters. Caraway is attacked by this pest in both years of vegetation. Heavily infested rosette leaves turn curly and malformed, then even wilt. In the second year the mites feed both on leaves and flowers. Infested foliage is covered with light spots, whereas the flowers become malformed, changing colour to pink, lilac or greenish. Their stamens and pistils are shapeless, resembling the petals. The mites develop within receptacle, thus the flowers degenerate. In consequence, the fruits may not set, but if so, they are minute and malformed. In the regions where this mite is abundant chemical control should be carried out. In the first growing season a double spray (in summer and early autumn) is required, whereas next year at least one treatment should be performed at the beginning of vegetation ().

Caraway crops are often infested with aphids. Leaves, shoots and umbels are usually populated by two: willow-carrot aphid (Cavariella aegopodii Scop.) and hawthorn-carrot aphid (Dysaphis crategi Kalt.). Also, root aphids, attacking most umbelliferous plants, can feed on caraway underground organs.

Chemical control should be conducted when the first aphid colonies appear on the crop. In the case of heavy infestation, the treatment should be repeatedly performed roughly at 10-day intervals. Some of insecticides recommended against Depresaria nervosa caterpillars can also effectively suppress aphid populations ().

Likewise other umbelliferous plants, caraway can be attacked by capsids, especially Lygus campestris L. and Lygus kalmi L. Damage is caused by both larvae and adults. Heavily infested plants turn yellow, then brown and finally dry up. Apart of direst harmless, capsids are known as carriers of various diseases. Chemical treatments against these pests are similar to those controlling the aphids.

Caraway crops can be also considerably affected by polyphagous pests such as grubs (Melolonthidae) and wireworm (Elateridae). If abundant, these pests should be eliminated with insecticides mixed with the soil in the year preceding a setting up of a plantation. Occasionally, caraway crop can be also invaded by rodents, particularly the vole (Microtus arvalis Pall.), field mouse (Apodemus agrarius Pall.) and wood mouse (Apodemus sylvaticus L.). All these pests gnaw the young plants and devour the roots during caraway winter dormancy. Rodents are difficult to be controlled, sometimes they are treated with exhaust fumes.

Caraway plants can be infected by numerous diseases (), however only a few of them are of a major importance. Elimination of seed-born diseases, especially those causing seedling damping-off, seems very essential. A quite efficient preventive measure is fungicidal seed-dressing just before sowing. During the vegetation season, caraway is often infected by downy mildew (Plasmopara nivea Schort.) which if intensive, can cause yellowing and wilting of the plants. Therefore, this pathogen should be treated with fungicides. Caraway stems can be attacked by basal root (Phoma anethi Sats.) and grey mould (Botrytis cinerea Pers.).

So called gangrene of inflorescence, caused by bacteria such as Erwinia, Pseudomonas and Xanthomonas, often appears while umbels are being formed and during flowering. In the Netherlands the most serious diseases of caraway are considered anthracnose (Mycocentrospora acerina) and white mould (Sclerotinia sclerotiorum). The first pathogen can be considerably limited by particular practices (e.g. lowering of N-fertilization and sowing rate), chemical treatments, and by biological control ().

 

Selections from the book: “Caraway. The Genus Carum”. Edited by Éva Németh. Series: “Medicinal and Aromatic Plants — Industrial Profiles”. 1998.