What to Do About Cotton Square and Boll Shedding? A Detailed Guide to Emergency Remedial Measures

When cotton grows under conditions of high temperature and abundant rain, large numbers of squares and bolls are often shed, producing plants that are tall, large and empty, leading to heavy yield losses. For different causes of shedding, corresponding emergency remedial measures can be taken.

Shedding due to prolonged drought: for cotton fields suffering long drought without rain and unable to be irrigated, the cotton plant leaves are thin and small, pale green to yellow in color, and the squares and bolls are shriveled and small; heavy rain causes shedding in large batches, light rain in small batches, and with no rain they gradually drop off.

Remedial measures: use 200 g of multi-element boron fertilizer plus 20 mL of Fengchanning per mu, dilute in 50 to 60 kg of water and spray evenly, then spray again after an interval of 7 days, for a total of 2 sprays.

Shedding due to abundant rain: the cotton field holds excessive moisture, and in some low-lying spots water accumulates and soaks the roots; the soil becomes compacted and loses permeability, nutrient supply is delayed, and the cotton leaves are green but thin and large; where water soaks the roots the leaves are yellow and thin, and the squares and bolls gradually shed.

Remedial measures: clear the three ditches, dig the cross-end ditch deeper, lower the groundwater level, drain off all standing water in low-lying spots, and then carry out intertillage and loosening of the soil. At the same time, use 30 g of cotton Geyechang, or 5 g of Lufeisu, or about 100 mL of Lufeng 95 per mu, dilute in 50-60 kg of water and apply as a foliar spray after 4 p.m., then spray again after an interval of 7 days, for a total of 2 sprays.

Shedding due to excessive shading: when the cotton field is too densely shaded and lacks light and ventilation, the lower cotton leaves first turn gray, then yellow, then shed, and at the same time large squares and small bolls also shed along with them.

Remedial measures: first remove some of the old leaves on the lower part of the main stem, and cut off the empty branches and empty leaves that bear no squares. For severely shaded cotton fields, the plants can be pushed together in rows to increase light exposure, or every other row can have the upper half of one row cut off, so as to achieve ventilation and light penetration. Where conditions permit, use 30 mL of 20% triadimefon (Fenxiuning) emulsion plus 10 mL of Penshibao per mu, dilute in 50 kg of water and spray evenly; this both prevents boll disease and prevents shedding.

Shedding due to boron deficiency: the symptoms are that some squares dry up on the cotton plant, some "form squares but do not flower", or the shedding rate gradually rises.

Remedial measures: for cotton fields severely deficient in boron, spray boron fertilizer at 50-100 g per mu each time, once every 7-10 days, for 4-6 consecutive sprays. For fields mildly deficient in boron, spray boron fertilizer once each at the early flowering stage, the full flowering stage and the mid boll-setting stage, using 50 g of multi-element boron fertilizer per mu, diluted in 50 kg of water and sprayed evenly after 4 p.m.

Shedding due to potassium deficiency: the symptoms are that the cotton stalks are thin and weak, the upper part of the main stem leans to one side, the fruiting branches droop, the leaf color fades, and the squares and bolls gradually shed.

Remedial measures: from squaring to the peak flowering and boll stage, spray a 0.2% to 0.5% aqueous solution of monopotassium phosphate per mu, once every 7 days, for 3-4 consecutive sprays, or apply 50-80 kg of plant ash as a top dressing per mu.

Shedding due to excessive vegetative growth: heavy water and heavy fertilizer cause the branches and stems to become loose, the leaves thick and large, and the tender tips to shoot up rapidly. This creates shading in the field and poor ventilation, and the squares and bolls gradually shed from the inside outward, until only 1 to 2 small squares remain at the top.

Remedial measures: according to the speed of excessive growth, spray 2-4 g of mepiquat chloride original powder per mu, which can alleviate the excessive vigor.

Shedding due to insect pests: the pests that harm squares and bolls and cause shedding include plant bugs, cotton bollworm, Asian corn borer and others; if these pests are not controlled in time, the larvae bore into and feed on the squares and bolls, causing shedding.

Remedial measures: before the larvae hatch out of the shell, when some of the eggs turn black, apply the pesticide 2 to 3 days later. Do not let the larvae bore into the squares and bolls, and shedding will stop.

Shedding due to lodging: when cotton grows into the middle and late stages, there are relatively many squares, bolls and flowers, and the load on the middle and upper parts of the plant is too great; if strong wind and heavy rain occur, the cotton plants will inevitably lodge, causing rotten bolls or shedding of squares and bolls in the lower and middle parts.

Remedial measures: promptly lift up the lodged cotton plants, press down firmly around the roots to prevent lodging again, and at the same time spray pesticide to protect the bolls. Use 50 g of Huangj injia plus 100 g of 50% carbendazim wettable powder per mu, or 30 mL of 20% triadimefon emulsion plus 100 g of Huoli Duoxiaosu, dilute in 50 kg of water and spray evenly.