What are the control methods for scale insects on camellias?

  How do you control scale insects on camellias? The common scale insects on camellias are mainly the red wax scale, the cottony cushion scale, the chaff scale, and the tea brown round scale. These scale insects all adversely affect camellia growth to some degree, so control measures must be taken promptly. The current control measures for scale insects on camellias are described below.

  I. Scale insects on camellias

  1. Red wax scale: The female adult's scale covering is hard and thick, 3-4 mm in diameter, with four white lines. It has one generation a year, and generally May to June is the peak period when large numbers of nymphs climb onto the twigs and cause damage.

  2. Cottony cushion scale: The female adult is orange-red, 5-7 mm long, with dense small black hairs all over and a white waxy substance on its back. When laying eggs, it secretes white cotton-like wax filaments, and a white waxy egg sac is attached to its abdomen. It has 2-4 generations a year, and damage is most severe from April to June.

  3. Chaff scale: The female scale covering is 1.5-2 mm long, with yellow or brown margins, named for its shape and color, which closely resemble chaff. It has 2-3 generations a year, and nymphs occur in early to mid-May, early to mid-July, and from late August to late September respectively.

  4. Tea brown round scale: The female scale covering is circular, 1-2 mm in diameter, raised in the center, sloping slightly downward from the center toward the edge, and golden yellow or reddish brown. The male scale covering is long oval or egg-shaped, with the scale point near one end. This insect mostly overwinters as second-instar nymphs.

  5. Scale insects usually cluster on young branches and leaf surfaces, using their specially structured piercing-sucking mouthparts to pierce and suck the sap from camellia stems and leaves, causing the branches and leaves to turn yellow and wither, the leaves to fall early, and even the whole plant to die. This insect is most likely to occur and spread under conditions of high temperature, high humidity, and poor ventilation.

  II. Control measures for scale insects on camellias

  1. When a small number of scale insects are found on camellia branches or leaves, they can be gently brushed off with a soft brush or removed with clear adhesive tape.

  2. In winter, spray lime sulfur mixture or rosin mixture to kill overwintering nymphs and so on.

  3. Spray pesticide at the peak of egg hatching, with the spring hatching period being the best time. It is easier to kill the insects by spraying before the scale covering has formed on the body surface. The pesticides that can be used include 40% omethoate emulsifiable concentrate at 1000 times dilution, 2.5% deltamethrin emulsifiable concentrate at 2500 times dilution, and 80% dichlorvos emulsifiable concentrate at 1000 times dilution; all have good insecticidal effects.

  4. When the scale covering has formed, spray 40% Supracide emulsifiable concentrate at 1500 times dilution for control, or in the early stage of scale insect occurrence, spray 25% buprofezin (mainly containing thiazinone) wettable powder at 1500-2000 times dilution, then spray once more after 15 days according to the pest situation.

How do you control scale insects on camellias?

The common scale insects on camellias are mainly four kinds: the red wax scale, the cottony cushion scale, the chaff scale, and the tea brown round scale.

Red wax scale:The female adult's scale covering is hard and thick, first rose red, later purplish red, 3 mm to 4 mm in diameter, with a navel-like top, lobed margins, and four white lines. It has one generation a year, and generally mid-May to early to mid-June is the peak period when large numbers of nymphs climb onto the twigs and cause damage.

Cottony cushion scale:The female adult is orange-red, oval, 5 mm to 7 mm long, with a raised back, dense small black hairs all over, and covered with a white waxy substance. When laying eggs, it secretes white cotton-like wax filaments, and a white waxy egg sac is attached to its abdomen, with 14 to 16 ridge-like raised lines on the sac. It has 2 to 4 generations a year, and all stages can overwinter. Damage is most severe from April to June.

Chaff scale:The female scale covering is 1.5 mm to 2 mm long, grayish white or gray, with yellow or brown margins, named for its shape and color, which closely resemble chaff. The male scale covering is narrow and long, with the two sides nearly parallel, about 1.2 mm long, and grayish white. It has 2 to 3 generations a year, and nymphs occur in early to mid-May, early to mid-July, and from late August to early September respectively.

Tea brown round scale:The female scale covering is circular, 1 mm to 2 mm in diameter, purplish brown or dark brown, hard and waxy, raised in the center, sloping slightly downward from the center toward the edge, with the shell surface somewhat like a round bamboo hat, and two scale points located in the center of the covering, golden yellow or reddish brown. The male scale covering is long oval or egg-shaped, with the scale point near one end. This insect mostly overwinters as second-instar nymphs.

Scale insects usually cluster on young branches and leaf surfaces, parasitizing most heavily on the undersides of leaves. They use their specially structured piercing-sucking mouthparts to pierce and suck the sap from camellia stems and leaves, causing the branches and leaves to turn yellow and wither, the leaves to fall early, and even the whole plant to die. Their excrement is rich in sugar liquid and often induces severe sooty mold, causing poor growth or death of the plant. This insect is most likely to occur and spread under conditions of high temperature, high humidity, and poor ventilation.

Control methods:

① When scale insects are found on individual branches or leaves, they can be gently brushed off with a soft brush or removed with clear adhesive tape.

② In winter, spray 0.5 degree lime sulfur mixture or rosin mixture to kill overwintering nymphs and so on.

③ Seize the peak period of egg hatching to spray, with the spring hatching period being the best time. Before the scale covering has formed on the body surface, it is easier to kill them with pesticide; you can spray 40% omethoate emulsifiable concentrate at 1000 times dilution, 2.5% deltamethrin emulsifiable concentrate at 2500 times dilution, or 80% dichlorvos emulsifiable concentrate at 1000 times dilution; all have good insecticidal effects.

④ When the scale covering has formed, you can spray 40% Supracide emulsifiable concentrate at 1500 times dilution, which also gives good control because of its strong penetration; or in the early stage of scale insect occurrence, spray 25% buprofezin (mainly containing thiazinone) wettable powder at 1500 times to 2000 times dilution, and spray once more after 15 days depending on the pest situation; the effect is quite good.

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