Everything you need to know about controlling pests of cucumber.
The principal cucumber insects include aphids, flea beetles, cucumber beetles (Spotted and striped), spider mites, squash bugs, squash vines borers, seed corn maggots, cut worms and pickle worms, but in general, all these insect-pests may not be serious in cucumber every year.
1. Red Pumpkin Beetle (Aulacophora Foveicollis Synonym Rhaphidopalpa Foveicollis Lucos):
As the name indicates, it is a bright red or gray colour beetle. Aulacophora cincta (Fabricius) and Aulacophora lewisii species have also been found damaging the cucumber crop. The first one is most destructive and is widely distributed all over the Southeast Asia as Mediterranean region towards West and Australia in the East.
In India, Aulacophora foveicollis and Aulacophora lewissii are found abundantly in almost all the states though more abundant in northern states, while Aulacophora cincta is more common in south India.
These beetles lay 150 to 300 eggs in cluster in soil near the base of the plant. Dry and water logged soils are not preferred for laying eggs, which are spherical in shape and yellowish pink in colour, becoming orange after a couple of days. Freshly hatched grubs are dirty white in colour, whereas, full grown once are creamy yellow and about 22 mm long. On hatching, the grubs feed on the roots and underground portion of host plants and also on fruits touching the soil.
The damaged roots and infested underground portion of stems start rotting due to secondary infection by saprophytic fungi. Infested fruits become unfit for human consumption. Adult beetles feed voraciously to seedlings (preferably cotyledons) or leaf lamina (leaf stage), making irregular holes. These beetles are active from. March to October with a peak period of activity from April to June.
i. Adopt cultural practices like clean cultivation, early sowing.
ii. Use only the resistant varieties for cultivation.
iii. Plough the infested field deeply soon after harvesting to kill the grubs present in soil.
iv. Dust the crop with 5% carbaryl, 4% Endosulfan, or spray with 0.2% carbaryl or 0.05% Endosulfan to safeguard the crop.
2. Striped and Spotted Cucumber Beetles (Acalymma Vittatum and Diabrotica Undecimpunctata):
The striped (Acalymma vittatum) and spotted (Diabrotica undecimpunctata) both are serious beetles feed on foliage and later on fruit, and transmit bacterial wilt, but the striped beetle spreads cucumber mosaic virus. Larvae feed on roots and stems.
The striped cucumber beetle has a black head and black and yellow striped wings, while the spotted cucumber beetle has a black head and a yellowish green body with twelve black spots on its back. Both the beetles are about 6 mm long. The adults appear in early spring and feed on cotyledons and new leaves.
i. Adopt cultural practices like deep summer ploughing, clean cultivation and early sowing.
ii. Dust the crop with 5% carbaryl powder during seedling development.
iii. Spray with methanol extracted neem seed kernel @ 4%.
3. Fruit Fly (Bactrocera Species):
In cucumber, the damaging fruit flies include Bactrocera cucurbitae (Coquillett), Bactrocera ciliatus (Loew), Bactrocera latifrons (Hendel), Bactrocera tau (Walker), and Bactrocera zonatus (Saunders) species. Abundance of these species except Bactrocera cucurbitae and Bactrocera ciliatus is specific to only certain areas. Among them Bactrocera cucurbitae is more common, destructive, and polyphagous in nature.
As many as 70 host plants have been listed by Batra (1953). The female flies puncture the soft and tender fruits with their stout and hard ovipositor, and each time lay 4 to 10 eggs per fruit below the epidermis. A single female can lay about 200 eggs in her life span of 8 to 10 weeks. The eggs hatch into maggots that feed inside fruits and cause rotting. The population is generally low during dry weather but increases rapidly with adequate rainfall. The fly attack is severe, especially after summer rains.
Control:
i. Grow resistant or early maturing varieties/hybrids.
ii. Bring changes in sowing dates, especially in areas where damage is observed every year.
iii. Collect and destroy all the infested fruits by burying more than 60 cm deep.
iv. Follow frequent raking of the soil under the vines.
v. Plough the infested field deep in hot summer months to kill the pupae.
vi. Spray carbaryl 0.1% at tender fruit stage (up to 5 days after fertilization).
vii. Adopt poison baiting or bait spray of 20 g malathion 50% WP or 50 ml diazinon 20% EC with 500 g molasses + 20 g yeast hydrolysate (if available) in two litres of water.
Note:
The control measures suggested should be undertaken as a cooperative campaign in all the fields in large areas, otherwise, the adults being good fliers will keep on migrating and invading from the neighboring fields in spite of one’s best individual efforts.
4. Aphids (Aphis Gossypii Glover):
Aphid, a very tiny (1.25 mm long) and yellowish dark green colour insect, is a major notorious pest of cucumber. Large colonies of greenish to brownish colour and wingless nymphs and adults are found on tender twigs and shoots and also on ventral surface of leaves. The affected parts due to sucking sap from the tissues turn yellow, curled, wrinkled, and deformed in shape and ultimately dry and die away.
Reduced fruit size and quality causes severe loss. The aphids also exude copious quantity of honeydew-like substance on which sooty mould develops which in turn hinders the photosynthetic activity of the vines, resulting in stunted growth. The fruits covered with sooty mould look unattractive and lose their market value. Besides damage caused by sucking sap from the vines, this insect transmits various viral diseases.
The pest is active throughout the year but maximum activity has been noticed during April to June. High humidity and cloudy weather with a little rainfall favour rapid multiplication of this pest. The nature of reproduction of this insect is parthenogenesis and viviparous both. A single female per day produces 8 to 22 nymphs that mature in 3-4 days, and total life cycle lasts for 7-9 days.
i. Clip-off and destroy the affected shoots and twigs immediately.
ii. Spray Malathion 0.1% or Metacid 0.1-0.2% at 10-12 days interval.
iii. Spray neem seed kernel extract (NSKE) @ 4% at weekly interval.
5. Mites (Tetranychus Cinnaborinus):
Mites are one of the most destructive pests of cucumber. The damage caused by nymphs and adults as sucking of sap and covering the leaves with thick webs on which soil particles deposit during windy weather. Random eggs webbing, which in turn affects the growth and development and results in leaf dropping of plants, can be observed on ventral surface of leaves. It also affects the flowering and fruit formation adversely.
Pre-oviposition period is 1 to 2 days, whereas, oviposition lasts for 8 to 12 days during March-September and 20 days during October-December but no egg laying in January and February. Fertilized female lays 61-93 eggs and unfertilized one 39-59 eggs. The eggs hatch in 2-6 days during April-October but take as long as 30 days in winter.
Larval and nymphal development takes 1-6 and.2-9 days during May-October in case of males and females and as long as 20 and 27 days during January-February, respectively.
The total life cycle is completed in 4-8 and 6-10 days during April-October in case of males and females, respectively and 50-57 days in winter. There may be as many as 32 overlapping generations in a year. This insect is more active during post monsoon period and the activity declines with a drop in temperature. Eggs are destroyed due to rain but its rapid multiplication starts after rainy season and continues until November.
i. Adequate supply of water in summer season and optimum dose of nitrogen discourages mites.
ii. Spray Neem Seed Kernel Extract (NSKE) @ 4% at weekly interval.
iii. Spray 0.05% Dicofol 18.5 EC (2.75 ml/l) or Vertimac 1.8 SL @ 0.8 ml/l at 15-20 days interval.
iv. Dust the crop with fine sulfur or spray with 0.1% wettable sulfur.
6. Leaf Miner (Phytomyza Horticola):
Now a day, leaf miner is becoming a very destructive insect in cucumber cultivation. Its activity is quite fast in the month of March-May. Young larvae make zigzag tunnels eating leaf below the epidermis. Adult moth lays eggs in the leaves through ovipositor by puncturing the leaves. Generally, female lays 25-300 eggs within 4-5 days. After hatching the maggots come out of the eggs in 2-3 days and larvae feed between the lower and upper epidermis making mines in leaves.
Maggots convert into pupae in 1-10 days, and pupae become adult within 7-12 days. They complete their life cycle within 12-20 days and complete 4-6 generations in a year. Tunneling causes loss of leaf chlorophyll, and heavy infestation results in curling of leaves and stunting of plant, which ultimately affect the growth and development of fruits adversely.
i. Remove and destroy severely infested leaves.
ii. Spray Thiomethoxane 25 WG @ 0.3 g/l or Deltamethrine @ 1.0ml/l of water at 15 days interval.
iii. Spray 4% neem seed-kernel powder (40 g/l of water) at an interval of 10 days.
7. Root Knot Nematode (Meloidogyne Incognita, Meloidogyne Hapla and Meloidogyne Javanica):
Cucumber crop is adversely affected by different root knot nematode in several parts of the country. Long, slender, and microscopic larvae attacked the roots. Initially, larvae enter into the root system and form galls. With the advancement of galls, the plant growth is stopped, leaves become yellow and smaller, and as a result, the yield is reduced drastically.
i. Apply Carbofuron 3G or Aldicarb at 25 kg/ha or Phorate 10 kg a.i./ha during field preparation.
ii. Use soil fumigant like Nemagan at 25 kg/ha for effective control of nematodes.
iii. Incorporate the neem cake @ 100-120 kg/ha in soil at final ploughing.