3.3 Chili thrips

Chili thrips, Scirtothrips dorsalis Hood, is a more recently introduced pest that was first reported in the US from Florida in 2004 and Texas in 2008 [11]. It has become a serious pest of multiple crops and has the potential to spread throughout the southern United States and in western states such as California [11]. Chili thrips adults (Figure 5) are tiny, only 1.2 mm in length [12, 13]. They are pale yellow in color except for their dark wings, which are bristle-like, and dark spots along the top of the abdomen that form an incomplete stripe. Immatures are pale yellow in color and lack wings.

Adults and immatures feed on young strawberry leaves causing darkening of the leaf veins near the leaf base [12, 13]. As the infestation progresses, the darkening

Figure 5. Chili thrips adult (photo credit: B. Panthi, UF).

Management of Strawberry Insect and Mite Pests in Greenhouse and Field Crops DOI: http://dx.doi.org/10.5772/intechopen.82069

becomes streaks on the leaves that can cover the entire leaf surface and lead to leaf deformation. Heavy infestations can cause stunting of entire plants. Infestations early in the season when strawberry plants are small and have only a few leaves cause the most damage.

Scouting for Chili thrips is best accomplished by looking for the injury they cause [12]. Leaves with the characteristic injury described above can be gently tapped over a white sheet of paper. This will dislodge any Chili thrips present, which will resemble tiny, yellow dashes crawling on the piece of paper. Thresholds have not yet been developed.

The predatory mite Amblyseius swirskii (Athias-Henriot) has shown some efficacy against thrips species in vegetable systems [14]. These predators feed primarily on eggs and immatures of thrips. This predatory mite is commercially available and has the potential to be used in other crops like strawberry. Insecticides should be avoided when possible because they cause disruption in the predator complex and cause thrips population to flare up. Insecticides should only be applied if the infestation is severe, particularly if thrips numbers are high early in the season.

#### 3.4 Aphids

leaves near the midvein and in flower buds. Infested leaves are small and wrinkled. High infestations can cause a compact mass of these leaves in the center of plants. Injury to leaves causes them to turn brown, wither, and die. Any fruit produced is

P. persimilis (a) adult and (b) eggs with twospotted spider mites and eggs on a strawberry leaf (photo credit: E.

Strawberry - Pre- and Post-Harvest Management Techniques for Higher Fruit Quality

Cyclamen mites can persist in perennial production systems, making them a greater threat to these systems [3]. They often come into a field on infested transplants and can also be transported by insects, birds, and even people via contaminated clothes or equipment. The threshold is low, 1 mite per 10 leaves in California [7]. Miticides must be applied in large volumes of water, 2839–4732 liters per

Chili thrips, Scirtothrips dorsalis Hood, is a more recently introduced pest that was first reported in the US from Florida in 2004 and Texas in 2008 [11]. It has become a serious pest of multiple crops and has the potential to spread throughout the southern United States and in western states such as California [11]. Chili thrips adults (Figure 5) are tiny, only 1.2 mm in length [12, 13]. They are pale yellow in color except for their dark wings, which are bristle-like, and dark spots along the top of the abdomen that form an incomplete stripe. Immatures are pale yellow in

Adults and immatures feed on young strawberry leaves causing darkening of the leaf veins near the leaf base [12, 13]. As the infestation progresses, the darkening

hectare, to ensure soaking of the developing tissues in the crown.

stunted and russety.

Figure 4.

M. Rhodes, UF).

3.3 Chili thrips

color and lack wings.

Figure 5.

106

Chili thrips adult (photo credit: B. Panthi, UF).

There are four species of aphids (Figure 6) commonly found in strawberries: the green peach aphid, Myzus persicae (Sulzer), the melon aphid, Aphis gossypii Glover, the potato aphid, Macrosiphum euphorbiae (Thomas), and the strawberry aphid, Chaetosiphon fragaefolii (Cockerell) [3, 7]. The strawberry aphid can severely affect yield because it transmits a host of virus including the strawberry mild yellow edge virus, strawberry crinkle virus and the strawberry mottle virus [7, 15]. In general, aphids are small (2.54 cm), globular, pear-shaped, soft-bodies insects found on the underside of leaves. Aphids are often various shades of green or yellow but can be black or even pink. There are winged and wingless forms. Aphids can be distinguished from similar insects by the two cornicles (tube-like structures) protruding from the end of the abdomen.

Winged females enter fields from nearby infested crops or weedy areas [3, 7]. They can also enter greenhouses. Female aphids can produce daughters without mating, so populations can build up very quickly. Aphids use their sucking mouthparts to feed on plant juices and excrete excess sugar as a sticky, sugary honeydew. Sooty mold fungus will grow on the honeydew and can contaminate fruit. Aphids efficiently transmit plant viruses. In strawberry production, these viruses are mainly a concern in nursery production. Viruses can also persist from one season to another in perennial production, but this is a rare occurrence.

Figure 6. Aphids on a grape leaf (photo credit: B. Achhami, UF).

Aphids rarely reach damaging levels in field grown strawberries [3]. Monitoring for aphids involves examining leaves in the field or collecting the leaves and examining them elsewhere. In Southern California, where they can be as issue, the threshold is 30% infested leaves from a sample of 100 leaves per hectare [7]. Yellow sticky traps can be used to monitor winged aphid populations and are especially useful in greenhouses.

In California, it is recommended to treat when the population appears to be

Management of Strawberry Insect and Mite Pests in Greenhouse and Field Crops

Whitefly nymphs are parasitized by tiny wasps, like aphids, and parasitized nymphs are black in color [3, 7]. Some whitefly parasitoids including Encarsia formosa and Eretmocerus spp. are available commercially and generalist predators, Delphastus spp. feed on them as well. Thorough coverage is essential when applying

Potato leafhoppers, Empoasca fabae Harris, are bright green leafhoppers [3, 16]. Nymphs are lighter green in color and wingless. The nymphs will move sideways when disturbed, which distinguishes them from other leafhoppers. Potato leafhoppers are larger than whiteflies and aphids, with adults being about 8.5 mm long. They overwinter in southern states with mild winters and migrate north as the weather warms up. They reach as far north as Canada. They generally reach North Carolina by early summer and continue north from there [16]. They feed and reproduce throughout the summer and fall until they are killed off by the first frost. Like the other sucking pests, potato leafhoppers are found on the underside of

Potato leafhoppers feed by sucking out plant juices. They prefer to feed on new growth. Unlike other sucking pests, potato leaf hoppers inject toxins into the plant tissue with their saliva [3, 16]. These toxins cause stunting, curling, and browning of leaves. This is often called "hopperburn" and resembles herbicide burn. In perennial strawberries, high amounts of hopperburn can cause reduced growth and yield in the next season. There are no established thresholds, but insecticides should

Many other mites and sucking insects are encountered in strawberry plantings. Most are encountered occasionally in small numbers. However, there is the potential for some to become pests. Spittlebugs, mealybugs, and stink bugs are examples

Spittlebugs, Cercopidae, are immature froghoppers. Adult froghoppers resemble leafhoppers but are usually larger and flatter than leafhoppers [17]. The nymphs secrete a frothy foam for protection (Figure 8) that resembles spittle, hence their common name. The species Philaenus spumaris (L.) can be a pest in strawberries,

Mealybugs, Pseudococcidae, are covered in waxy or mealy secretions for protection [17]. Adults are small and oval in shape with well-developed legs. Currently, there are no major mealybug pests of strawberries, but several species are serious pests of other crops and ornamentals. However, mealybugs are sometimes seen in

Stink bugs, Pentatomidae, are a family of true bugs that are shield shaped and secret foul-smelling chemicals when disturbed [17]. Many species are various shades of green or brown. Other species, like the harlequin bug, Murgantia

histrionica (Hahn), sport very bright colors. Some stink bug species, like the harlequin bug and southern green stink bug, Nezara viridula (L.), are major pest species [17]. Some of these pest species can be found in strawberries but rarely build up to damaging numbers. Other species of stink bug are predatory, like the well-known spined soldier bug, Podisus maculiventris (Say), and feed on other insects [17]. It is

increasing at a rapid rate and parasitism levels are low [7].

DOI: http://dx.doi.org/10.5772/intechopen.82069

be applied before hopperburn becomes widespread.

primarily because the foam can be annoying to pickers [3].

strawberries, so it is important to be aware of them [3].

insecticides.

leaves.

of these.

109

3.6 Potato leafhopper

3.7 Other sucking pests

Aphids have many natural enemies and it is important to take parasitism into consideration when deciding if a spray is necessary. Parasitized aphids, often called mummies, are swollen, brown, and sometimes have a hole chewed in the abdomen if the adult parasitoid wasp has emerged [3, 7]. The adult parasitoids are tiny wasps that lay eggs in aphids. The larvae develop inside the aphids, feeding on the aphid from the inside out and killing it in the process. The larva pupates in the aphid mummy and the adult wasp chews a hole in the aphid to emerge and begin the cycle again. Several aphid parasitoids are available commercially and are particularly effective in greenhouses. Green lacewing larvae, Chrysoperla rufilabris (Burmeister) and other generalist predators will also prey on aphids.

#### 3.5 Whiteflies

There are many species of whiteflies (Figure 7) that can be found in strawberry [3, 7]. These include the bandedwing whitefly,Trialeurodes abutilonia (Hold.), greenhouse whitefly,T. vaporariorum (West.), iris whitefly, Aleyrodes spiroeoides Quaintance, silverleaf whitefly, Bemisia argentifolii Bellows & Perring, and the strawberry whitefly,T. packardi (Morrill). Whitefly adults are yellowish in color with white wings. Immatures, called nymphs, resemble scale insects. The first immature stage is a crawler that moves a short distance from the eggs before becoming sedentary and forming its protective scale. The final nymphal stage is nonfeeding and often called a pupal stage. All stages are found on the underside of leaves. Adults and nymphs suck plant juices and produce honeydew like aphids. Whiteflies can also vector some viruses.

Whiteflies are typically not an important pest in strawberry but can be more of a nuisance pest [3]. They are of concern in greenhouse strawberry production and in field production in California [7]. In California, the greenhouse whitefly vectors pallidosis-related decline of strawberry [7].

Adult whiteflies can be monitored using yellow sticky traps [7]. One trap per 25 hectares should be hung from a stake just above the crop canopy and checked weekly. It is important to monitor nymphs at the same time. This is done by checking 20 mature leaves from each field quarter. There is no treatment threshold.

Figure 7. Whiteflies on a squash leaf (photo credit: D. frank, UF).

Management of Strawberry Insect and Mite Pests in Greenhouse and Field Crops DOI: http://dx.doi.org/10.5772/intechopen.82069

In California, it is recommended to treat when the population appears to be increasing at a rapid rate and parasitism levels are low [7].

Whitefly nymphs are parasitized by tiny wasps, like aphids, and parasitized nymphs are black in color [3, 7]. Some whitefly parasitoids including Encarsia formosa and Eretmocerus spp. are available commercially and generalist predators, Delphastus spp. feed on them as well. Thorough coverage is essential when applying insecticides.

#### 3.6 Potato leafhopper

Aphids rarely reach damaging levels in field grown strawberries [3]. Monitoring for aphids involves examining leaves in the field or collecting the leaves and examining them elsewhere. In Southern California, where they can be as issue, the threshold is 30% infested leaves from a sample of 100 leaves per hectare [7]. Yellow sticky traps can be used to monitor winged aphid populations and are especially

Strawberry - Pre- and Post-Harvest Management Techniques for Higher Fruit Quality

Aphids have many natural enemies and it is important to take parasitism into consideration when deciding if a spray is necessary. Parasitized aphids, often called mummies, are swollen, brown, and sometimes have a hole chewed in the abdomen if the adult parasitoid wasp has emerged [3, 7]. The adult parasitoids are tiny wasps that lay eggs in aphids. The larvae develop inside the aphids, feeding on the aphid from the inside out and killing it in the process. The larva pupates in the aphid mummy and the adult wasp chews a hole in the aphid to emerge and begin the cycle again. Several aphid parasitoids are available commercially and are particularly effective in greenhouses. Green lacewing larvae, Chrysoperla rufilabris (Burmeister)

There are many species of whiteflies (Figure 7) that can be found in strawberry

Whiteflies are typically not an important pest in strawberry but can be more of a nuisance pest [3]. They are of concern in greenhouse strawberry production and in field production in California [7]. In California, the greenhouse whitefly vectors

Adult whiteflies can be monitored using yellow sticky traps [7]. One trap per 25

hectares should be hung from a stake just above the crop canopy and checked weekly. It is important to monitor nymphs at the same time. This is done by checking 20 mature leaves from each field quarter. There is no treatment threshold.

[3, 7]. These include the bandedwing whitefly,Trialeurodes abutilonia (Hold.), greenhouse whitefly,T. vaporariorum (West.), iris whitefly, Aleyrodes spiroeoides Quaintance, silverleaf whitefly, Bemisia argentifolii Bellows & Perring, and the strawberry whitefly,T. packardi (Morrill). Whitefly adults are yellowish in color with white wings. Immatures, called nymphs, resemble scale insects. The first immature stage is a crawler that moves a short distance from the eggs before becoming sedentary and forming its protective scale. The final nymphal stage is nonfeeding and often called a pupal stage. All stages are found on the underside of leaves. Adults and nymphs suck plant juices and produce honeydew like aphids.

and other generalist predators will also prey on aphids.

Whiteflies can also vector some viruses.

pallidosis-related decline of strawberry [7].

Whiteflies on a squash leaf (photo credit: D. frank, UF).

useful in greenhouses.

3.5 Whiteflies

Figure 7.

108

Potato leafhoppers, Empoasca fabae Harris, are bright green leafhoppers [3, 16]. Nymphs are lighter green in color and wingless. The nymphs will move sideways when disturbed, which distinguishes them from other leafhoppers. Potato leafhoppers are larger than whiteflies and aphids, with adults being about 8.5 mm long. They overwinter in southern states with mild winters and migrate north as the weather warms up. They reach as far north as Canada. They generally reach North Carolina by early summer and continue north from there [16]. They feed and reproduce throughout the summer and fall until they are killed off by the first frost. Like the other sucking pests, potato leafhoppers are found on the underside of leaves.

Potato leafhoppers feed by sucking out plant juices. They prefer to feed on new growth. Unlike other sucking pests, potato leaf hoppers inject toxins into the plant tissue with their saliva [3, 16]. These toxins cause stunting, curling, and browning of leaves. This is often called "hopperburn" and resembles herbicide burn. In perennial strawberries, high amounts of hopperburn can cause reduced growth and yield in the next season. There are no established thresholds, but insecticides should be applied before hopperburn becomes widespread.

#### 3.7 Other sucking pests

Many other mites and sucking insects are encountered in strawberry plantings. Most are encountered occasionally in small numbers. However, there is the potential for some to become pests. Spittlebugs, mealybugs, and stink bugs are examples of these.

Spittlebugs, Cercopidae, are immature froghoppers. Adult froghoppers resemble leafhoppers but are usually larger and flatter than leafhoppers [17]. The nymphs secrete a frothy foam for protection (Figure 8) that resembles spittle, hence their common name. The species Philaenus spumaris (L.) can be a pest in strawberries, primarily because the foam can be annoying to pickers [3].

Mealybugs, Pseudococcidae, are covered in waxy or mealy secretions for protection [17]. Adults are small and oval in shape with well-developed legs. Currently, there are no major mealybug pests of strawberries, but several species are serious pests of other crops and ornamentals. However, mealybugs are sometimes seen in strawberries, so it is important to be aware of them [3].

Stink bugs, Pentatomidae, are a family of true bugs that are shield shaped and secret foul-smelling chemicals when disturbed [17]. Many species are various shades of green or brown. Other species, like the harlequin bug, Murgantia histrionica (Hahn), sport very bright colors. Some stink bug species, like the harlequin bug and southern green stink bug, Nezara viridula (L.), are major pest species [17]. Some of these pest species can be found in strawberries but rarely build up to damaging numbers. Other species of stink bug are predatory, like the well-known spined soldier bug, Podisus maculiventris (Say), and feed on other insects [17]. It is

Figure 8. Spittlebug protective frothy foam. The spittle bug nymphs are underneath the foam and cannot be seen (photo credit: E.M. Rhodes, UF).

important to properly identify any stink bug causing concern in strawberries to make sure it is not a beneficial predatory species.
