2024 Author: Gavin MacAdam | [email protected]. Last modified: 2023-12-16 13:38
The fruit-shifting leafworm is an ubiquitous pest that attacks almost any fruit tree. Overwintered caterpillars are especially harmful, invading developing fruit buds and eating away their contents from the inside. As a result, the buds dry out, turn brownish and crumble. And some time later, the caterpillars begin to twist the leaves, which take on the appearance of loose lumps. In addition, they can damage both ovaries and flower buds. If you do not stop the harmful activity of gluttonous parasites in time, you can lose an impressive part of the crop
Meet the pest
The fruiting changeable leafworm is a discreet butterfly with wingspan ranging from 17 to 21 mm. The front wings of the pests from the basal part are characterized by a brownish-brownish color, white spots near the inner edges and a slight bluish tinge. And the upper parts of the front wings are painted in grayish tones with black or brownish strokes. Sometimes there are individuals with grayish-bluish strokes. As for the hind wings, they have a gray-brown tint.
Transparent oval eggs of fruiting changeable leaf rollers are gradually colored in milky white tones. Greenish-olive caterpillars, covered with small thorns, grow in length from 18 to 20 mm. And caterpillars of younger ages are often painted white and yellow. The length of dark brown pupae ranges from 9 to 14 mm. All of them are endowed with cremasters in the form of truncated cones, equipped at the apices with eight hook-shaped bristles. Wintering of third instar caterpillars takes place in cracks in the bark in cocoons, as well as under dry foliage and in branching branches.
With the onset of April (closer to the green cone phase), voracious caterpillars begin to leave their wintering places and actively bite into young buds. And some time later, they pull together young buds and leaves into balls, inside which they are fed. In general, the development of caterpillars takes about twenty five to thirty days and ends approximately at the end of May.
When the petals of the apple trees begin to crumble en masse, the harmful parasites will begin to pupate. As a rule, this period lasts until mid-June, and pests pupate either in places of feeding, or between leaves tied together by cobwebs. On average, the development of each pupa takes from eight to fourteen days. And after the apple trees bloom, in twelve or fourteen days, the butterfly years starts, lasting from fifteen to twenty days.
Fertilized females lay eggs either in small groups (each of them contains from two to eight eggs), or one at a time, placing them both on the upper surfaces of the leaves and on the lower ones. Very rarely, the eggs of fruiting variable leaf rollers can be found on fruits. The total fertility of these pests is quite high and amounts to about two hundred eggs.
After eight to twelve days, the reborn caterpillars begin to skeletonize the lower leaf surfaces, and upon reaching the third age (this happens in the middle of summer) they go to wintering places. In one year, only one generation of fruit volatile leaf rollers has time to develop, however, these parasites have time to harm them quite strongly.
How to fight
Old and infected branches must be cut from trees in a timely manner. As for spraying, they can be carried out with both biological products and insecticides. Such drugs as "Rogor-S", "Di-68", "Fufanon" and "Desant" have proven themselves especially well - ten grams of any of them are taken for every ten liters of water. And pheromone traps help to keep track of the number of gluttonous parasites.
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