Plant beneficial pest- Nabidae (part 4)

The insect family Nabidae contains the damsel bugs. The terms damsel bug and nabid are synonymous. There are over 400 species. They are soft-bodied, elongate, winged terrestrial predators. Many damsel bugs catch and hold prey with their forelegs, similar to mantids. They are considered helpful species in agriculture because of their predation on many types of crop pests, such as cabbage worms, aphids, and lygus bugs.

Damsel bugs of the genus Nabis are the most common. They and other genera are most numerous in fields of legumes such as alfalfa, but they can be found in many other crops and in non-cultivated areas. They are yellow to tan in colour and have large, bulbous eyes and stilt like legs. They are generalist predators, catching almost any insect smaller than themselves, and cannibalizing each other when no other food is available.

Plant beneficial pest-Geocoris(part 3)

Geocoris is a genus of insects in the family Lygaeidae (although sometimes the subfamily is elevated to the family "Geocoridae"). Commonly known as the big-eyed bug, Geocoris is a beneficial predator often confused with the true chinch bug, which is a pest.

Big-eyed bugs are true bugs in the order Hemiptera. The two most common species are Geocoris pallens and Geocoris punctipes. Both are predators and occur in many habitats, including fields, gardens, and turf grass. Big-eyed bugs are considered an important predator in many agricultural systems and feed on mites, insect eggs, and small insects such as pink boll worm, cabbage loppers and white flies. Adult big-eyed bugs are small (about 3 mm) black, gray, or tan with proportionately large eyes. Eggs are deposited singly or in clusters on leaves near potential prey. They develop with incomplete metamorphosis (there is no pupa) and take approximately 30 days to develop from egg to adult depending on temperature. Both nymphs and adults are predatory, but can survive on nectar and honeydew when prey are scarce. Big-eyed bugs, like other true bugs, have piercing-sucking mouth parts and feed by stabbing their prey and sucking or lapping the juices. Although their effectiveness as predators is not well understood, studies have shown that nymphs can eat as many as 1600 spider mites before reaching adulthood, while adults have been reported consuming as many as 80 mites per dayinsects such as pink boll worm, cabbage loppers and white flies. Adult big-eyed bugs are small (about 3 mm) black, gray, or tan with proportionately large eyes. Eggs are deposited singly or in clusters on leaves near potential prey. They develop with incomplete metamorphosis (there is no pupa) and take approximately 30 days to develop from egg to adult depending on temperature. Both nymphs and adults are predatory, but can survive on nectar and honeydew when prey are scarce. Big-eyed bugs, like other true bugs, have piercing-sucking mouth parts and feed by stabbing their prey and sucking or lapping the juices. Although their effectiveness as predators is not well understood, studies have shown that nymphs can eat as many as 1600 spider mites before reaching adulthood, while adults have been reported consuming as many as 80 mites per day

Plant pest –Caterpillars (part 2)

Caterpillars have been called "eating machines", and eat leaves voraciously. Most species shed their skin four or five times as their bodies grow, and they eventually pupate into an adult form. Caterpillars grow very quickly; for instance, a tobacco hornworm will increase its weight ten-thousand fold in less than twenty days. An adaptation that enables them to eat so much is a mechanism in a specialized midget that quickly transports ions to the lumen (midget cavity), to keep the potassium level higher in the midget cavity than in the blood.

                                                                A Gypsy Moth caterpilars

Most caterpillars are solely herbivorous. Many are restricted to one species of plant, while others are polyphagous. A few, including the clothes moth, feed on detritus. Most predatory caterpillars feed on eggs of other insects, aphids, scale insects, or ant larvae. Some are cannibals, and others prey on caterpillars of other species (e.g. Hawai'ian Eupithecia ). A few are parasitic on cicadas or leaf hoppers. Some Hawai'ian caterpillars (Hyposmocoma molluscivora) use silk traps to capture snails

                                       Hypsipyla grandela damages mahogany in Brazil

Caterpillars cause much damage, mainly by eating leaves. The propensity for damage is enhanced by monoculture  farming practices, especially where the caterpillar is specifically adapted to the host plant under cultivation. The cotton bollworm causes enormous losses. Other species eat food crops. Caterpillars have been the target of pest control through the use of pesticides, biological control and agronomic practices. Many species have become resistant to pesticides. Bacterial toxins such as those from Bacillus thuringiensis which are evolved to affect the gut of Lepidoptera have been used in sprays of bacterial spores, toxin extracts and also by incorporating genes to produce them within the host plants. These approaches are defeated over time by the evolution of resistance mechanisms in the insects.

Plants evolve mechanisms of resistance to being eaten by caterpillars, including the evolution of chemical toxins and physical barriers such as hairs. Incorporating host plant resistance (HPR) through plant breeding is another approach used in reducing the impact of caterpillars on crop plants

Plant pest- Cabbage Moth (part 1)

The Cabbage Moth (Mamestra brassicae) is a common European moth of the family Noctuidae.

This species varies considerably in size, with a wingspan of 34–50 mm. The fore wings are brown and mottled with a prominent white-edged stigma and a broken white sub terminal line. The hind wings are grey, darker towards the termen. The prominent spur on the tibia of the foreleg is a diagnostic feature, though is best viewed with a magnifying lens. This moth has a rather complex life history: two or three broods are produced each year and adults can be seen at any time from May to October, occasionally at other times [The flight season refers to the British Isles. This may vary in other parts of the range.  ]. It flies at night and is attracted to light, sugar and nectar-rich flowers.

The larva is green or brown with dark spots. As the common and scientific names suggest, it can be a pest of cultivated brassicas but it feeds on a wide range of other plants . Due to its complex life history, this species overwinters either as a larva or a pupa

Source : Wiki