Distribution, occurrence and fruitfulness giant sumpweed in Steppe of Ukraine

Cyclachaena xanthiifolia (Nutt.) Fresen

The considerable part of small-scale production and presence of the big areas of not processed lands in Steppe of Ukraine promote to distribution and moving of some weeds which had until recently no essential value in field husbandry, and nowadays become as threat for growing of many agricultural crops.

One of such species is giant sumpweed (Cyclachaena xanthiifolia (Nutt.) Fresen), revealed not only on ruderal habitats and in sowings of some field cereal crops and tilled crops, fodder and vegetable crops [6, 7].



At introduction in new ruderal vegetative groupings giant sumpweed quickly superseded from them a number of other species of weeds and became as dominant from participation part in them from 44 to 100% [8].

In sowing of agricultural crops of Steppe of Ukraine frequency of its occurrence for last seven years has increased almost in 2,5 times.

Noticeable decrease in productivity of grain crops began already at presence giant sumpweed in crops of  2 pieces/m², and at 5 pieces/m² productivity decreased for 43,6% [2, 3].

At the same time, its distribution threatens not only essential decrease in productivity of agricultural crops, and negative influence on health of people and animals owing to inhalation of its pollen which quantity on one plant exceeds 50 – 55 million pieces, and weed impurity in hay and green weight serve as the reason of gastric diseases of animals [1, 3, 5,].

For prevention of distribution and development of effective ways of the control of giant sumpweed in crops and out of their the features of growth, development, contamination level, frequency of occurrence and an abundance and fruitfulness in different agrophytocenoses and out of them remain studied insufficiently. In this connection the definition of frequency of occurrence, character of distribution, an abundance and seed efficiency of giant sumpweed in segetal  and ruderal ecotops was the purpose of our researches.

Technique of researches. Field experiences, observance and estimates carried out during 2006 – 2012 in special and industrial crops of economies of steppe northern and North central subzones of Northern steppe zone. The contamination of crops, frequency of occurrence and an abundance of weeds was determined by the standard techniques [4,7].

The estimate of seed efficiency conducted on 10 plants by direct calculation or with weight method by means of grains thrashing from plants, definition of its general weight and weight of 1000 grains and with the subsequent recalculation of fruitfulness of one plant [9, 10].

Results of researches. The greatest frequency of giant sumpweed occurrence is established on typical ruderal habitats, in particular on dumps, manure – pits, roadsides of roads (R = 93 – 96%). The frequency of giant sumpweed occurrence  was  little  – at edges of fields, laylands, along streets, channels, dams, field-protective strips of forest (R = 54 – 62%), insignificant – in tilled crops and garden cultures, thinned  herbages of long-term grasses, flower beds, etc. (R = 14 – 24%) whereas in crops of winter and early summer cultures there were only single plants of its.

Data of observation indicate to high viability and ecological plasticity of giant sumpweed as on ruderal and segetal ecotopes. So, on ruderal habitats the plants of giant sumpweed, not having natural wreckers and illnesses, and not being eaten by animals, formed continuous thickets with average height of plants to 201 – 244 cm and powerful above ground crude mass (to 5,0 – 7,0 kg/m²). Seed efficiency of each plant in such herbages reached 28 – 39 thousands pieces, and at free growth of plants and favorable conditions of the nutrition and provision with water – to 69 – 138 thousands pieces. And about   75 – 80% of seeds was sheded on the earth, and 20 – 25 % of seeds were kept on plants till the spring not losing viability, they dispersed with wind, water and animals on considerable distances from parent plants.

The seeds of giant sumpweed were brought from ruderal habitats in crops of cultural plants by the wind, water, animal, agricultural machines and tools. In particular, before the beginning of spring field works in 0 – 30 cm a layer of soil on edges of the fields weedy with giant sumpweed, it has been revealed 32,4 thousands pieces/m² seeds of this weed, on distance of 20 m from field edge – 23,0 thousands pieces/m², 50 m – 16,1 thousands pieces/m², 100 m – 6,9 thousands pieces/m², 200 m – 1– 2 thousands pieces/m².

Germination of seeds occurred from depth of 1 – 6 cm at temperature of air 3 –5 ºС and above, and mass shoots appeared in the end of April – in the beginning of May and coincided with shoots of the majority of summer grain, fodder and vegetable cultures. On ruderal habitats the abundance of shoots of giant sumpweed made from 165 to 637 pieces/m², whereas in cultivated crops and garden cultures – 36 – 64 pieces/m², summer grain and leguminous – 9 – 12 pieces/m², winter and forage crops – 1– 3 pieces/m². Quantity of shoots on many fields too considerably decreased in process of removal from edges of fields and on distance of 300 – 500 m made in corn crops 1– 3 pieces/m², vegetable cultures – 1 – 7 pieces/m², sunflower – 1– 6 pieces/m².

In cultivated crops and vegetable cultures under favorable hydrothermal conditions the majority of shoots of weeds (to 70%) appeared, as a rule, simultaneously with shoots of cultural plants, and under droughty conditions the period of occurrence of shoots was extended. They appeared from a phase of shoots of sunflower, corn, sorghum, etc. and before formation on these plants 9 – 12 and more leaves.
Giant sumpweed differs in crops of cultural plants in considerable height (to 166-224 cm) and weight of the crude above ground mass (to 1,6 – 7,2 kg/of m²). It strongly exhausts and dries up soil, suppresses, and quite often and entirely "muffles" not only undersized vegetable and melon crops,  and tall cultures, in particular, sunflower, corn, sorghum etc., reducing their productivity on  20 – 25% and it is more.

The most part (60 – 100%) seeds of giant sumpweed for harvest time of sunflower, corn and other late cultures reached a full maturity of grain and partially was showered or gathered together with the crop of cultural plants. Fruitfulness of one plant of giant sumpweed in crops of sunflower, corn, sorghum averaged 6,8 – 13,3 thousands pieces, and at free growth in crops – 14,8 – 16,9 thousands pieces. The fruitfulness was still above on irrigated fields of vegetable cultures (tab. 1).

Table 1
Abundance and fruitfulness of giant sumpweed in crops and ruderal habitats

Habitat	Weeds, pieces / m 2			Height  of  plants, см	Dry weight of plants, g/m2	Fruitfulness of 1 plant, pieces
	1*	2*	3*			average	maximal
Winter wheat	3	1	6**	47,3	40,3	48	363
Оats	11	4	9**	62,8	50,4	312	957
Corn	43	22	8	166	140	8993	14753
Sunflower	51	27	11	170	110	6769	11974
Sorghum	36	20	5	203	190	13317	16845
Melon crops	64	29	18	211	210	24800	96888
Vegetable (on an irrigation)	57	33	20	224	400	31278	49877
Edges of fields	316	158	37	209	370	37456	89883
Roadsides of roads	165	91	30	201	310	28016	69122
Dumps	637	342	51	244	630	39123	137520

Notes: * 1) 1-2 decades of May; 2) 1-2 decades of June; 3) 3 decade of September-1 decade of
October ** on the fields which have been not processed after harvesting.

In the spring in dense sowings of winter and summer grain and forage crops on initial phases of development of the plant of giant sumpweed slowed down growth and development and in a depression state were to the phase of milk-wax and full ripeness of grain of cultural plants, reaching 10 – 15 cm of height and 30 – 70 g weights of the crude above ground part, and essentially did not influence on the productivity of cultural plants. But after harvesting the most part cut, and under favorable conditions and new plants, intensively grew and accelerated development to the beginning-end of autumn, forming the viable seeds which quantity reached from 0,05 – 0,30 to 0,4 – 1,0 thousands pieces on 1 plant. The seeds were sloughed, closed up in soil and were as source of contamination of the subsequent cultures of the crop rotation.

Conclusions. In Northern steppe zone of Ukraine the greatest frequency of occurrence giant sumpweed was observed on ruderal habitats (R = 54 – 96%) where the abundance of it shoots reaches 165 – 637 pieces/m², and average fruitfulness of plants exceeds 28 – 39 thousands pieces.
The occurrence of weeds on the fields of cultivated and garden cultures is less (R = 14-24 %), an abundance of shoots does not exceed 57– 64 pieces/m², average seed efficiency of plants – 6,7– 24,8 thousands pieces. In crops of winter and summer cultures meet only its single plants with average seed efficiency from 0,05 – 0,3 to 0,4 – 1,0 thousands pieces.

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