The Harm Caused by Mulberry Longhorn Beetles to Fig Trees and How to Control Them

Figs are not only easy to propagate and cultivate, but also a treasure among fruits and medicines. Figs have thin skin and no seeds, are sweet and soft as honey, with a rich fragrance, a unique flavor, and abundant nutrition. They contain large amounts of vitamin A and C, as well as a variety of organic acids and more than 17 kinds of amino acids. The vitamin C content is 2 to 3 times that of citrus, 8 times that of peaches, and 2 to 7 times that of pears.

The Harm Caused by Mulberry Longhorn Beetles to Figs

The mulberry longhorn beetle is widely distributed and is the main pest of fig trees. Symptoms of damage: the mulberry longhorn beetle mainly damages the branches and trunk of fruit trees. Adults gnaw the bark of tender branches, leaving irregular strip-like scars; in severe cases the bark of the branches is gnawed bare, causing fruiting branches to break easily and die. Adults lay eggs in the middle of notches on the branches and trunk. After the eggs hatch, the larvae bore downward inside the branches and trunk along the xylem and pith, and can bore all the way to the roots, causing poor plant growth, premature decline of tree vigor, and affecting the fruit yield of that year; moreover, the cold hardiness of the tree decreases, making it prone to freezing damage, and in severe cases the whole plant dies. The mulberry longhorn beetle overwinters as larvae in the burrows of the branches and trunk. In early to mid-March the overwintering larvae begin to emerge and become active, and April to May is the peak period of damage. In late May the mature larvae move upward along the burrow and make a pupal chamber to pupate. Adults emerge in mid to late June and immediately gnaw the bark of new fig shoots and lay eggs on the branches and trunk. Early August is the peak egg-laying period. Newly hatched larvae bore directly into the xylem to feed and develop toward the base of the trunk; the burrow of a single larva over its lifetime reaches 1.5 to 2.5 m in length. In mid to late November the larvae stop feeding and enter the overwintering state.

Integrated Control Methods for the Mulberry Longhorn Beetle

1. Cultivation control. Because the mulberry longhorn beetle prefers to feed on mulberry trees and oak trees, mulberry or oak trees can be used as trap tree species. That is, plant mulberry or oak trees more than 100 m away from the fig orchard as an isolation and protection belt. During the occurrence period of the mulberry longhorn beetle, spray the mulberry trees for control, and make sure the control of the trap trees is timely and thorough. This reduces the pest source and the harm to fig trees.

2. Manual control. Before adults appear, apply whitewash (made from 10 parts quicklime, 1 part sulfur, and 40 parts water) to the trunk and large branches to prevent adults from laying eggs. During the adult occurrence period of the mulberry longhorn beetle, catch the adults in the morning and evening. In July to August, manually dig out the eggs; check the egg-laying notches every 7 to 10 days, and at the notches use a small knife to pierce the eggs or kill the newly hatched larvae. Checking and digging out eggs 2 to 3 times can control the damage of larvae boring into the trunk.

3. Chemical control. During the larval occurrence period, when fresh moist frass holes are found, first use a wire to remove all the frass, then insert aluminum phosphide tablets into the frass holes and seal the holes tightly with sticky mud for fumigation. Alternatively, use a veterinary syringe to inject a 40 to 50 times dilution of 40% omethoate emulsifiable concentrate into the frass holes, then plug the holes with mud to prevent the liquid from flowing out.

What Pests Do Figs Have  

1. Mulberry longhorn beetle  

Adults first appear in early to mid-June, with the peak in mid to late June. The adult egg-laying period is from mid-June to early August, and eggs are often laid on shoots about 30 cm from the surface or on two-year-old large branches. When laying eggs, the adult gnaws a “u” or “T” shaped notch in the bark and xylem and lays l egg. Damage by small larvae is very easy to spot: wherever reddish-brown frass is seen, there must be a larva inside. The larvae bore downward through the bark, overwinter in the phloem, and the following spring bore into the xylem to feed. In May to June of the third year the mature larvae pupate, and in June to July they emerge as adults.  

Control methods: from June to July each year during the adult egg-laying period, manually catch and kill them; for fig trees that had pest damage the previous year, in April to May and September to October, at the last larval frass hole on the branches or trunk, use a liquid injector to inject a 50 times dilution of 80% dichlorvos emulsifiable concentrate or 40% fenitrothion into the insect hole. Or dip absorbent cotton in the pesticide and insert it into the insect hole, which gives good larval control. Alternatively, before the newly hatched larvae have bored into the xylem, choose a strongly systemic insecticide, such as a 100 times dilution of 40% omethoate or a 100 times dilution of 10% miechongjing, and spray the branches, trunk, and egg-laying sites.  

2. Yellow slug moth  

Adults appear in mid-June and lay eggs on the underside of leaves; the egg stage lasts 7 to 10 days. The larvae cause damage from mid-July to late August, feeding only on the leaf flesh. They leave the leaf veins and eat the leaves into a net-like pattern; after the larvae grow larger, they eat the leaves into notches, leaving only the petiole and main veins.  

Control methods: during the larval stage, spray a 1500 to 2000 times dilution of 90% trichlorfon, or an 800 to 1000 times dilution of dichlorvos, or an 800 times dilution of Bacillus thuringiensis, all with relatively good control effects; tie a toxic ring at the main trunk branching point to kill mature larvae crawling down the trunk to the ground; take advantage of their phototaxis by setting lights to trap and kill them, which can also be used to predict pest conditions. 

3. Black velvet chafer  

The larvae feed on fig tree roots, while adults mainly feed on fig tender branches and new leaves and like to gather and feed voraciously. The larvae feed on young roots, and by autumn the third-instar mature larvae bore 20 to 30 cm deep into the ground to make a soil chamber and pupate; the pupal stage lasts about l0 days before emergence, and the emerged adults do not come out of the soil but enter the overwintering state.  

Control methods: during the peak adult occurrence period, around 5 o'clock in windless conditions, dip poplar (or willow) branches and leaves in a 200 times dilution of 80% trichlorfon, and insert one bundle every 10 to 15 m in the nursery or newly planted young tree area to trap and kill adults; alternatively, soak poplar (willow) branches in a 50 times dilution of 50% monocrotophos for more than 10 hours, insert 5 bundles per mu into the ground to trap and kill adults; soil treatment.

Ecological Habits of Figs  

They like a warm and humid maritime climate, like light and fertilizer, are not cold-tolerant, not waterlogging-tolerant, but are relatively drought-tolerant. In the inland areas of North China, if the temperature drops to -12°C, new shoots are prone to freezing damage, and at -20°C the aboveground parts may die, so winter cold protection is extremely important. Figs tolerate poor soil and have strong soil adaptability, especially strong salt tolerance, but cultivation is most suitable in fertile sandy loam.  

The leaves are broad and large, and the fruit is peculiar. In summer and autumn the fruit hangs in abundance. It is an excellent courtyard landscaping and economic tree species, has the characteristic of resisting a variety of toxic gases, tolerates smoke and dust, and has few pests and diseases. It can be used for factory and mining area landscaping and household sideline production. The leaves, fruit, and roots can be used as medicine. Its only weakness is low cold resistance, so planting should choose a sunny, wind-sheltered, warm place. Propagation and cultivation: mainly by cuttings, but also by sowing or layering. If cuttings are taken in the first year, fruit can be borne in the second year, and the full fruiting period is reached in 6 to 7 years. If planted beside garden paths, lawns, ponds, and buildings, it can add to the scenery.  

The fig tree has luxuriant branches and leaves and an elegant tree form, with fairly good ornamental value, and is a good ornamental tree species for garden and courtyard landscaping. Besides field planting and courtyard planting, figs can also be grown in pots.

From the name fig, we can see that it is a relatively special plant: it can bear fruit without blooming. Understanding its pests and prevention methods is very important for growing figs, as this can increase its yield and improve the efficiency of cultivation work.