Pests
Grapholita delineana Walker. - Eurasian Hemp Moth.
Systematic position.
Class Insecta, order Lepidoptera, family Tortricidae, subfamily Olethreutinae, tribe Grapholitini, genus Grapholita.Synonyms.
Laspeyresia delineana Walker, G. apicatana Wlk., G. mundana Chr., G. quadristriana Wlsm., G. sinana Feld., G. terstrigana Rag., G. tetragrammana Stgr.Biological group.
Pest of hemp.Morphology and biology.
Wingspan 11.5 mm in male, 15 mm in female. Sexual dimorphism for adults. Forewings strongly varying in color from light brownish-ocherous to dark brownish-red. Outer margin of forewing bearing 9 oblique light yellow stripes directed backward. Four slanting light yellow stripes located in the middle of inner margin. Fringe of forewing is dark gray with metallic shine. Hindwings grayish-brown; fringe grayish-brown, with a dark line along the base. Egg light yellow, transparent, oval, 0.6 mm in length, with thin and wrinkled shell. Caterpillar light yellow to bright red, 8-12 mm in length, with light yellow-red head. Prothoracic shield light yellow and transparent. Abdominal legs with 16-20 hooks forming a uniserial crown. Pupa light brown, 5-7 mm in length, with 2 rows of spinules directed backward on dorsal side of 2nd-8th segments. Caterpillars of the last (usually 5th) instar winter in the cocoons covered with soil particles and located at roots, in a surface soil layer to a depth of 5-10 cm, within plant residues in fields, in places of thrashing, retting, storing, and also in thickets of wild growing hemp. Females of spring generation lay eggs one by one or by 2-3 on the lower side of hemp leaves (to 60% of eggs), on their upper surface (to 30%), on stalks and petioles (about 10%). Moths of the subsequent generations lay eggs in abundance on inflorescences. Fertility of females of the wintered generation is 100-200 eggs on average, and 350-500 eggs in the subsequent generations. Caterpillars hatch in 8-10 days at temperature 20-22° C. Caterpillars of spring generation skeletonize hemp leaves on lower side near ribs, from 2nd instar gnawing holes in leaf petioles and in stalks at hemp growth stage of 4-5 leaves. Later, the caterpillars creep upward along stalks, gnawing new holes. Sometimes 20-50 caterpillars simultaneously feed on one plant. Duration of their feeding is 21-33 days. Caterpillars of 2nd and 3rd generations gnaw holes in small stalks, eat away buds, flowers, and especially seeds. Caterpillars of summer generation develop one month. Pupation of caterpillars of summer generations occurs mainly in stalks, seeds, and braided leaves. Development of pupae lasts 16-22 days.Distribution.
South-Palearctic species have initially West-Palearctic and East-Asian populations, penetrating into the Oriental Realm. It now inhabits Middle and Southern Europe, Asia Minor, Iran, North India, East China (from Heilongjiang to Sichuan), Korea, Japan; North America (invasive since 1943). In the former USSR, the Hemp Moth is distributed in the south of the European part (Moldova, Ukraine, Northern Caucasus), in Transcaucasia, the Far East; i.e., in the south of Khabarovsk Territory, in Primorski Territory, in the south of Sakhalin, in Southern Kurils (Kunashir). In the 1960s it was most likely brought with seeds to Kyrgyzstan (Chu Valley), but was not marked there after 1969. Kazakhstan (Kuznetsov, 2005) was probably included in the area of distribution instead of Kyrgyzstan.Ecology.
The species has 3 generations (last one is incomplete) in the south of Ukraine, in Moldova and Kabardino-Balkaria. First caterpillars appear in spring on soil surface at daily average temperature 7°C in mid-April, leaving atfter one month. At rapid rise of temperature, some caterpillars pupate in cocoons in ground. Pupation begins at DD 70 (at threshold 10.4°C). Moths of 1st generation fly from mid-May to the end of June, second generation from 1st or 2nd third of July to the last third of August, the third generation from the end of August to the last third of September. Flight of the wintered moths begins at accumulation of DD 155-161, coinciding with flowering of white acacia (locust). Decrease of humidity to 40% causes death of 80% of eggs. Flight of moths of the 2nd generation coincides with the growth stages of flowering and formation of seeds. The generations overlap, and all stages of the Hemp Moth development meet during the vegetation period. DD for summer generation development are 637-646. Caterpillars of the 3rd generation eat mainly seeds. Having no time to finish their development before harvesting, the usually perish. The majority of caterpillars diapause by the end of August under the influence of seasonal change of daylight hours. At least 22 hymenopteran species parasitize on the Hemp Moth, killing up to 38.5% of caterpillars and 14.5% of pupae.Economic significance.
The Hemp Moth has low economic significance because of great reduction in the number of areas producing cultural hemp recently (approximately 6,000 hectares in Russia and 3,000 hectares in Ukraine). In the 1960s it was considered a dangerous pest of seeds and stalks of the technical and seed hemp, causing high yield losses in all areas of this crop cultivation in the south of the European part of the USSR. In Ukraine, yield losses of hemp seeds were 30-40%, stalks were damaged sometimes by 100%. Besides hemp, the pest also slightly damages hop, both cultural and wild growing. In Primorskii Territory, caterpillars of the insect are marked on wild growing Japanese hop (Humulus scandens). Damaged young plants droop and wither, and plants that survive form gall swellings on stalks 1-2 cm long or excrescences in places of penetration and exit of the caterpillars. Destruction of growing-point results underdevelopment, deformation of stalk and formation of lateral shoots. As a result, the yield and economical quality of fiber are sharply reduced. During both the vegetation period and winter, fields show spotted distribution, especially along field edges. Agronomical control measures include maintenance of crop rotation and spatial isolation of new hemp fields from prior year, stubbling, deep autumn plowing, and other actions. Biological measures include the use of pheromone traps for monitoring of populations. Chemical measures are fumigation of hemp seeds, insecticide treatments during leafing-out against 1st generation caterpillars, and later against 2nd generation caterpillars.Reference citations:
Danilevskii A.S. & Kuznetsov V.I. 1968. Tortricidae, tribe Laspeyresiini. Moscow & Leningrad: AN SSSR, 636 p. (Bykhovskii B.E., ed. Fauna of the USSR, new ser., N 98. Lepidoptera. V. 5(1)) (in Russian).Kostyuk Yu.A. 1974. Family Tortricidae. In: Vasil.ev V.P., ed. Pests of agricultural crops and forest plantations. V.2. Arthropods. Kiev: Urozhai, p. 261-320 (in Russian).
Kuznetsov V.I. 1994. Family Tortricidae. In: Kuznetsov V.I., ed. Insects and mites . pests of agricultural plants. V. 3(1). Lepidoptera. St.Petersburg: Nauka, p. 51-234 (in Russian).
L.vovskii A.L. 1981. Tortricidae. In: Kopaneva L.M., ed. Key to harmful and useful insects and mites of industrial cultures in the USSR. Leningrad: Kolos: 170-175 (in Russian).
Senchenko G. I. & Timonina M.A., eds. 1978. Hemp. Moscow: Kolos, 286 p. (in Russian).
Tkalich P.P., Lepskaya L.A. & Goloborod.ko P.A. 1983. System of hemp protection. Zashchita rastenii 1: 46-49 (in Russian).