Lecture 02 Leaf Eating Insects: 1- Leaf Chewing Insects: the Important Leaf Biting Insects Belong to Different Insect Orders, with Different Ways of Feeding
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Plant Protection Dept. 3rd Stage Students Practical Forest Insects Mr. Hazim S. Ahmed and Mrs. Dlpak B. Yaba Lecture 02 Leaf eating insects: 1- Leaf chewing insects: The important leaf biting insects belong to different insect orders, with different ways of feeding. There are examples of insects feeding on certain parts of plant but most of these insects start biting from the leaf edge toward the inside. (1) Oak leaf cut worm, Euproctis melania Order: Lepidoptera Family: Lymantriidae Description: Adult insect is a medium sized moth, with slow flight and the body covered with silver white scales. The female larger than the male and at the end of the abdomen there is a tuft of scales. The larvae are Eruciform, green in color then changes to yellowish brown or gray color in general. The body covered by dense hairs. Damage: The small larvae bite the epidermis of the leaf then it attacks the buds and cause damage and death in the spring. The large larvae eat most of the parts and in the severe or heavy infestation leaves, the insect cause complete defoliation of the trees. The body of the larvae is covered with dense hairs and contains blister secretions to the skin (or cause irritation to the skin). 7 Plant Protection Dept. 3rd Stage Students Practical Forest Insects Mr. Hazim S. Ahmed and Mrs. Dlpak B. Yaba (2) Gypsy Moth, Lymantria dispar Order: Lepidoptera Family: Lymantriidae Description: Adult: Male moths are much smaller than females and have a wing span of 35 to 40 mm. Females have a wing span of 55 to 70 mm. Males are brown whereas females are mainly white. Both sexes have a dark, crescent-shaped mark on the forewing. Both sexes have also pectinate antennae. Larva: The 1st (3 mm) and 3rd (7 mm) instars are black with long hairs; the 2ndinstar (5 mm) is brown with short hairs. Instars 4, 5 and 6 are similar to each other and may be light to dark gray with flecks of yellow. They have long hairs that may be dark or golden and have 2 rows of tubercles along the back. Normally 5 pairs of blue tubercles are followed by 6 pairs of red; however variations are known to occur including all 11 pairs of tubercles being blue. Egg: Egg masses are approximately 30 to 60 mm long and 20 to 30 mm wide and may contain 100 to 1000 eggs. Damage: The larvae are voracious feeders especially in the old ages, and the heavy infestation lead to complete defoliation of the trees. During the first three instars, gypsy moths prefer foliage of a limited selection of trees (apple, aspen, birch, larch, oak, willow, alder, hazel, etc.), however once larvae gets to approximately 2 cm in size (third instar), it starts to consume foliage of many more trees, such as spruce, pine, chestnut and hemlock. As majority of foliage is consumed by larvae in the last two instars, very wide variety of trees can be affected. 8 Plant Protection Dept. 3rd Stage Students Practical Forest Insects Mr. Hazim S. Ahmed and Mrs. Dlpak B. Yaba (3) Pine processionary caterpillar, Thaumetopoea pityocampa Order: Lepidoptera Family: Thaumatopoeidae Description: Adult: The female moth has a wingspan of 36-49 mm. The wingspan of the male is 31-39 mm. The antennae are filiform in females and pectinate in males. Both sexes have a hairy thorax. The abdomen is stout and its last segments are covered with a tuft of large scales; the abdomen of the male is brushy and sharp. The forewings are dull ashen-grey; the veins, margins and three transverse bands are darker. The hindwings are white, grey-fringed, with a characteristic dark spot in the anal region. Larva: The larvae develop through five instars, recognized by differences in head capsule size. The full-grown caterpillar is about 40 mm in length. The head capsule is black. The body of the first-instar caterpillar is dull apple-green. The integument and hairs that clothe the body vary considerably with different provenances. In general, the integument is darker in colder areas and varies from dull bluish-grey to black. The pleural hairs vary from white to dark yellow; the dorsal hairs range from yellow to dull orange. Damage: The larvae feed on all types of pine trees and cause complete defoliation and weakness of the trees. The silk nests made by larvae affect the terminal growths of the branches and become dry and their color change to red. The larvae also cause severe inflammations to humans especially on fingers and eyelids and this make the people afraid from visiting the forest and this decreases its importance. 9 Plant Protection Dept. 3rd Stage Students Practical Forest Insects Mr. Hazim S. Ahmed and Mrs. Dlpak B. Yaba (4) Pistachio processionary bud moth, Thaumetopoea solitaria Order: Lepidoptera Family: Thaumatopoeidae Description: In generally, the color of adult body was gray. The wingspan is 20–28 mm for males and 25– 35 mm for females. The head V shape, the female eyes were brown and the male eyes were dark brown color. In both sexes, antennae were on the shoulders, which were yellowish brown color, bi- pectinate type and have a hairy thorax with darker gray hairs in male. The larvae have a cylindrical shape, black head, there a light colored, on each segment there are ten hair tufts, four tuft hairs on each plural side; the fourth pair of plural side is larger than ventral tuft hair and there is a pair of tuft hair on the dorsal layer. Damage: The larvae feed in spring (April to June) on pistachio and sociable on the host plants which they defoliate. 10 Plant Protection Dept. 3rd Stage Students Practical Forest Insects Mr. Hazim S. Ahmed and Mrs. Dlpak B. Yaba (5) Oleander hawk-moth, Daphnis nerii Order: Lepidoptera Family: Sphingidae Description: The adult insect is a large sized moth, its length about (4cm) and its color is pale or light green with crossed lines with different colors like light yellow grey and brown. Damage: The caterpillars feed mainly on oleander (Nerium oleander) leaves, a highly toxic plant but the insect are immune to this toxicity. They may also feed on most plants of the Dogbane family, such as Adeniumobesum, Tabernaemontanadivaricata and Alstoniascholaris. 11 .