**6. Pests on strawberry plants**

Many pests damage strawberry plants and important pests are included in this section.

*Frankliniella occidentalis* Perg., *F. intonsa* Trby. (Thysanopthera: Thripidae): *Frankliniella occidentalis* and *F. intonsa* are thought as the dominant species in strawberry fields. Depending on the temperature, it can give 22 offspring per year. After the thrips spend the winter on the soil and various plants as adults, they pass to the strawberry with the formation of flower buds. In particular, flower-time populations are increasing [102]. They begin to feed with the opening of flower buds in strawberries. They damage the strawberry flower and fruit by absorbing the plant sap. As a result of suction, flower drop, low yield, small and seed fruit formation, and tanning are observed. Fruits become deformed and lose their market value [103].

On the other hand, it causes secondary damage by infecting viruses such as Thrips stylets and Tomato Spotted Wilt Virus [104]. Since it reaches a high population in a short time, there are difficulties in chemical control [103]. Weed cleaning is important in strawberry fields as a cultural precaution in the control of thrips. *Orius sp.* (Both: Anthocoridae), *Coccinella septempunctata* (Col: Coccinellidae), *Syrphus sp.* (Dip: Syrphidae), *Chrysoperla carnea* (Neur.: Chrysopidae), *Adalia bipunctata* (Col: Coccinellidae) are known. The most effective predator is *Orius sp.* has been reported. Chemical control should be done when 10 thrips/flower is determined in the flower counts in strawberry fields [102].

*Tetranychus urticae* and *T. cinnabarinus* are some of the most common pests on strawberries (**Figure 5**).

Common names of them are used as two-spotted spider mites or greenhouse red spider mites [105]. With the warming of the air in the spring, the spider females, which pass from the surrounding weeds to the strawberries, lay their eggs in the web they weave on the lower surface of the leaves. Therefore, the density of the networks gives information about the population. Small yellow spots and tanning are seen on the damaged leaf because of feeding by the red spider. A female can lay 100–150

#### **Figure 5.**

*Adults and nymphs of* Tetranychus urticae *(left) and* T. cinnabarinus *on strawberry plant and* Tetranychus urticae *adult and egg on strawberry plant (right).*

eggs in her lifetime. It completes one offspring in 10–20 days. The strawberry plant is controlled, and the damaged leaves are removed from the environment as a cultural precaution. It can be counted as controlling weeds on the edge of the garden. Biological control of *P. persimilis, Neoseiulus fallacis* (Garman) (Acari: Phytoseiidae), *Neoseiulus californicus* (McGregor), and *Galendromus occidentalis* (Nesbitt); are crucially important [106–108].

*Anthonomus rubi* Herbst (Coleoptera: Curculionidae): Adults of *Anthonomus rubi,* which started to appear from the flower bud period of strawberries. It especially feeds on the young leaves and flowers of strawberries. Females lay 1 egg in an unopened bud. During egg-laying, it pierces the flower stem and prevents the circulation of the sap [105]. The flower bud it lays eggs does not develop, dries up, remains on the branch, and finally falls. This form of damage is unique to *A. rubi*. The main damage is caused by females cutting the flower bud stalks while laying eggs and feeding the larvae inside the bud. The egg hatches after 5–10 days. The larval period is 14–20 days. The pupal period is about 8 days [105]. Adults emerge by piercing the flower buds at the end of June and mid-July. After feeding for a few days, it enters the summer-winter diapause; the pest gives 1 offspring per year. In high populations, bud damage can be 5–90%, and yield loss can be 60% or more. The damage rate is higher in early varieties. The main host is strawberry. Raspberry, blackberry, rose, and wild rose from the Rosaceae family are other important hosts [105].

*Phytonemus pallidus* (Banks): *Phytonemus pallidus* (Banks) is a pest that causes serious yield losses in strawberries [109]. It causes damage by feeding on the newly emerging young leaves, especially in the crown of the strawberry plant (**Figure 6**). Hardening, wrinkling, discoloration, and a brittle structure are observed in the sucked leaves. An increasing population is stunted and decreases both in size and number of fruits [109]. However, it can cause the death of the strawberry plant [109].

Each female individual lays approximately 90 eggs under suitable conditions and becomes an adult from an egg in 2 weeks [109]. For this reason, it can reach dense populations in a short time. As a cultural precaution in control, using healthy plant material and alternating. It is important to pay attention to the cleanliness of the garden. Strawberry plants should be examined in the spring, especially young and mature leaves. The control method should be decided according to the population situation. In its biological control, *Amblyseius cucumeris* and *A. reticulatus* Oudemans (Acarina: Phytoseiidae) species are effective in reducing the population as predators [109]. If an average of 10 individuals per leaf is detected, recommended plant protection products should be used [110].

**Figure 6.** Phytonemus pallidus *(banks) on strawberry plants.*

*Lygus spp.* (Hem.: Lygaeidae): *Lygus elisus* (Van Duzee), *L. hesperus* (Knight), and *L. lineolaris* (Palisot de Beauvois) have been reported as species that cause extensive damage to strawberries [109]. These species are polyphagous species that damage flowers and young fruits in strawberries. Deformations and formation of seeded strawberry fruits are seen in damaged fruits. Strawberries lose their market value in dense populations and cause great economic losses. Lygus population is more concentrated in strawberry fields with weeds. The pest, which spends the winter as an adult, gives 3–4 offspring depending on the conditions during the year. It takes 30–40 days from egg to adult. In the cultural control, foreign vote control should be carried out around the strawberry production area, and plant protection products should be used, which are recommended by paying attention to the pest population in the controls made before flowering in the chemical control [110].

*Spodoptera littoralis* (Boisduval) (Lepidoptera: Noctuidae): It is an important polyphagous pest species commonly found in the world [111–114]. Although the main host of the pest is cotton, it can cause economically significant losses in many industrial and field crops, vegetables, and fruits [112–116]. They damage the leaves and fruits of the strawberry. Especially in the case of products such as cotton and corn around the strawberry field, it causes an increase in the pest population [115].

*Chaetosiphon fragaefolli* (Hom.: Aphididae): In general, adults and nymphs of Aphids live in colonies near the veins in the crown, fresh shoot, leaf, and underside of the strawberry [109]. Adults and nymphs of aphids feed by sucking plant sap on strawberry leaves [109]. As a result of feeding, damage in the form of curls, deformities, and yellow spots occurs on leaves and fresh shoots. These pests spend the winter in the egg period they lay on the branches and shoots of fruit trees.

*Chaetosiphon fragaefolii* spends all stages of its life on strawberries, including overwintered eggs, nymphs, wingless adults, and winged adults [105]. In addition, they cause fumagine by the development of saprophytic fungi on the sweet matter they secrete during feeding. By covering the plant surface with fumagine, the respiration of the plant is prevented. As a result of the inhibition of plant respiration, the development of the strawberry plant is weakened. As a result of adversely affecting plant development, yield and quality loss occur. For this reason, strawberry loses their market value. Cytorhabdoviruses such as strawberry aphid, Strawberry crinkle virus (CV), and Strawberry mild yellow edge virus (MYEV) cause significant damage by infecting healthy plants [117–119]. The main hosts of strawberry aphids are wild and cultivated strawberry plants (*Fragaria spp.*, *Potentilla anserina*, *F. virginianana, F. vesca*). In its control, clean seedlings should be used in the greenhouse and in the open field as cultural measures, Aphid-infested plants and weeds should be cleaned, Plant stems and weeds remaining on the ground after harvest should be destroyed. In terms of biological control, species of predators, especially Coccinellidae, Chrysopidae, and Syrphidae families, parasitoids *Aphidius spp.* are important natural enemies. Chemical control should be decided according to the population density [105].

Leafhopper (Cicadellidae): These species, which are polyphagous pests, cause damage by absorbing the plant sap from the vascular system of the plant. The toxic saliva they secrete causes injury to the plant. Short petiole and small leaf formation are seen in the damaged strawberry plant [109]. In addition, deformations in the mid-vein angle of the leaves are observed. These symptoms can be confused with Strawberry vein banding virus symptoms, but they are not the harmful Strawberry vein banding virus vector. Control: Leaf surface can be checked by visual inspection method, adults can be detected with methods such as sweep net, yellow sticky trap. In case of increased density, recommended insecticides can be used [109].

Cercopidae families of some species cause serious damage in areas with high humidity. Nymphs surround themselves with this substance by secreting a white foamy substance 1–2 cm wide. The pest that takes its name from this substance causes serious production losses [109]. If the pest is not controlled, the damage will continue until the harvest. Nymphs pierce plant roots and feed on plant sap. After feeding on the roots, it moves towards the green part of the strawberry. As a result of the feeding of nymphs, plant growth stops, small, irregularly shaped fruit formation is observed in strawberries. It causes a loss in yield. Insecticides should be used for chemical control [109].

*Otiorhynchus spp*., (Col.:Curculionidae): *Otiorrhynchus spp.* They lay their eggs on the soil surface, and the hatched larvae feed on strawberry roots and cause damage. *Otiorrhynchus spp*. Larval damage rate increases in sandy soils and plastic mulching. Adults also feed on strawberry leaves. Strawberry damaged because of feeding weakens, bushes, fades, and eventually, the plant dies. On the other hand, Black root rot pathogen infection can be seen in the feeding area [109]. As a cultural precaution in its control, it should avoid growing strawberries in contaminated areas. Plastic mulching should be avoided as it increases larval damage. Chemical control should be carried out in line with the recommended practices [110].

Various soil pests feed on the roots of strawberries and can cause plants to wilt and dry out. Among these pests (*Agriotes spp.), Tipula spp*. (leatherjackets), (Melolonthidae), centipedes (eg *Scutigerella spp.*), (*Agrotis spp.)* and (Noctuidae spp.). In order to decide on the control, it is necessary to have information about the populations of these pests in the soil. Strawberry plants can be recommended to be cultivated and ventilated before planting. Recommended insecticides should be used in chemical control [110].

In general, snails feed on plants at night and hide among plant wastes in the garden during the day. As a result of feeding, small and medium-sized deep holes are formed in ripe strawberry fruits. This sign of damage can be confused with other insect pests [109]. Generally, these holes are seen in silver color in snail damage. Snails generally become active depending on the soil temperature. Suitable for snail development in humid weather conditions. Elimination of favorable conditions for its survival as a cultural precaution in its control helps in the control of this pest. For example, rocks, wood, leaves, dry leaves, and excessive mulching provide shading. Fermented food traps and commercial food traps are used as biotechnical control [109].

*Drosophila suzukii* Matsumara 1931 (Dip: Drosophilidae): *Drosophila suzukii* is a polyphagous pest that was first identified in Japan in 1916. It damages all fruits with a soft structure, such as strawberries, during ripening and harvest [120]. Female individuals can easily lay eggs on the strawberry fruit, especially with their saw-like ovipositor (**Figure 7**). The larvae that emerge from the eggs feed on the fruit flesh of the strawberry and cause the main damage to the fruit (**Figure 7**). The larvae complete their development and become pupae on or outside the strawberry fruit. Later, adults emerge from the pupae (**Figure 7**). Damaged strawberry fruit.

softens and collapses (especially when you touch it, it feels empty) and loses its market value (**Figure 7**). The pest can multiply rapidly in a short time and reach a high population. *Drosophila suzukii* emerges from egg to adult in 8 days at 25°C. An average female lays 400–600 eggs [121]. Irrigation should be done with a drip irrigation system in gardens. Equipment that may cause the spread of the pest to other places should be kept clean [105]. Biological control: *Anthocoris nemoralis* (Hemiptera: Anthocoridae) and *Orius spp.* (Hemiptera: Anthocoridae) and as pupal parasitoids, *Pachycrepoideus vindemmiae* (Pteromalidae) and *Trichopria drosophilae* (Diapriidae) are known to be effective on *D. suzukii* population [105]. Biotechnical Control: Traps should be hung from the time of Strawberry Fruit coloration. As traps, 8–10 holes with a maximum size of 3 mm are drilled on 0.5 lt transparent plastic containers. 100–300 ml of apple cider vinegar is put into the plastic container. Strawberry is hung on its habitus with the help of support. Insecticides recommended for chemical control should be used [105].

#### **Figure 7.**

Drosophila suzukii *ovipositor structure and egg (left),* Drosophila suzukii *female and male adult individuals (middle), Drosophila suzukii damage and larvae in strawberry (right).*
