Guava

On sandy Florida soil with a bad history, a large container is the realistic answer.

A tree that stays stunted and unthrifty despite feeding and watering, with small pale leaves and dieback at the tips. Wilting on hot afternoons in soil that is plainly moist. Poor response to fertilizer. Dig gently at the root zone and look for heavily knotted, swollen, distorted roots - the galls of this species are large and unmistakable. Trouble is concentrated on sandy soils and on ground that has grown susceptible crops before.

There is no home cure once a tree is infested. Heavy mulching and organic top-dressing keep pushing new feeder roots and can carry a declining tree for years, but they do not eliminate the nematode. Severely affected trees are best removed and replaced in fresh ground or a large container. Where this species is regulated, report suspected finds to your state agriculture department rather than moving plants or soil off the property.

Buy nursery stock from a reputable source and inspect the roots before planting - this nematode moves in infested plants and soil, which is why it is regulated. Do not plant guava into ground where nematode-stunted plants have already failed, and do not move soil or plants from an infested area. Add heavy organic matter and mulch, which builds the soil life that suppresses nematodes, and interplant French marigolds. Growing in a large container of clean mix avoids the problem completely and is a sensible choice on sandy soil with a known history.

Meloidogyne enterolobii, commonly called the guava root-knot nematode, is a microscopic soil roundworm that is far more damaging than the common root-knot species and is a regulated pest in parts of the southeastern United States. It invades guava roots and forms large knotted galls that block water and nutrient uptake, and infested trees decline steadily - stunted, yellow, wilting in heat, and eventually dying. It has destroyed guava plantings in Florida and elsewhere, and it also attacks tomato, pepper, sweet potato, and other crops, including varieties bred to resist ordinary root-knot nematodes.

Its wider significance in Hawaii, where it threatens native ohia, is the reason plant-movement rules exist there.

Vivid yellow to orange powdery pustules on new leaves, shoot tips, flower buds, and young fruit - the color is unmistakable and unlike any other guava problem. Purple-rimmed spots on young leaves before the spores appear. Twisted, stunted, or blackened shoot tips, defoliation of new growth, and repeated dieback that leaves a tree pushing flush after flush and never getting anywhere. Damage is concentrated entirely on young tissue; mature leaves are not attacked.

Prune out infected shoots and buds well below the damage, bag the prunings rather than composting them, and disinfect tools afterward. Protective fungicides labeled for the crop and applied to new flushes give real control in a wet season, but they protect new growth rather than curing infected tissue, and repeat applications are needed while the tree is flushing. Report suspected finds in areas where the rust is regulated, particularly in Hawaii.

Avoid pushing soft new growth into warm wet weather - time nitrogen feeding so flushes come in drier periods, and prune to open the canopy so foliage dries quickly. Space plants and do not water overhead. Buy clean nursery stock and inspect it, since the rust moves most often on plants. In Hawaii, do not move myrtle-family plants or cuttings between islands or into the state, and follow state quarantine guidance - the rust is a documented threat to native ohia forest there. Some guava selections are less susceptible than others, but no cultivar is immune.

A fungal rust (Austropuccinia psidii, formerly Puccinia psidii) that attacks the young growth of guava and its relatives in the myrtle family - eucalyptus, bottlebrush, allspice, rose apple, and the Hawaiian native ohia. It infects new leaves, shoot tips, flowers, and young fruit, producing brilliant yellow-orange powdery spore masses, then distorting and killing the tissue. It thrives in warm humid weather and spreads on wind, clothing, tools, and nursery plants. It is present in Florida, Hawaii, California, and the Gulf, and in Hawaii it is a serious threat to native forest, which is why moving myrtle-family plant material there is restricted.

Bagging and weekly windfall collection are not optional for a usable crop; picking firm at color break also helps, since the flies favor softening fruit.

Tiny puncture or sting marks on the skin of ripening fruit, sometimes with a weeping drop or a small sunken dimple around them. Fruit that softens, browns, or collapses on one side well before it should. Small white maggots in the flesh when the fruit is cut, and fruit that falls early and rots fast. Adult flies - larger than a housefly, with patterned wings - hovering around ripening fruit and resting on foliage in the morning. Windfalls under the tree squirming with larvae, which is where the next generation comes from.

There is no cure for fruit already infested - bin it sealed, and never leave it lying. Protein bait sprays are the standard commercial control and are what agriculture departments use in outbreaks; in a home garden, sanitation plus bagging does most of the work. If you find a fruit fly outside its normal range, or receive a quarantine notice, report it to your state agriculture department rather than dealing with it privately: several of these species are regulated, and it is illegal to move host fruit out of a declared quarantine area, including to friends and family in another county or state.

Bag the fruit. A paper, mesh, or organza bag slipped over each fruit once it reaches golf-ball size physically excludes the females and is the only home control that reliably works. Pick fruit at color break and finish ripening it indoors rather than letting it soften on the plant, which removes the window the flies need. Clear every fallen fruit at least weekly and dispose of it by bagging, deep burial, or solarizing in a sealed bag in the sun - never in an open compost heap, which just breeds more. Keep trees pruned small enough that you can actually reach and bag the crop. Hanging traps tell you when flies are active but will not protect a crop on their own.

Tephritid fruit flies lay their eggs under the skin of ripening fruit, and the maggots feed inside it, so the first sign is usually a fruit that looks fine and is full of larvae when cut. The Caribbean fruit fly is established across peninsular Florida and the Caribbean; Mediterranean and Oriental fruit flies are established in Hawaii and turn up in California, Texas and Florida as quarantine outbreaks. They prefer fruit that is beginning to soften and color, they build up on any fallen fruit left rotting on the ground, and populations run from late spring through fall. Because several of these species are regulated pests, an infestation is not only a garden problem - moving infested fruit is how quarantines start.

Bagging fruit and picking at color break protects the crop and cuts the seed birds carry away. Rats, raccoons, and possums work the same fruit at night.

Fruit disappearing from the outermost, most exposed parts of the plant first, and from the top of a tree where you cannot reach anyway. Single neat pecks and gouges in ripening fruit, with several fruits sampled rather than one eaten through - the classic sign that it was birds rather than an animal. Heads of grain or seed going visibly lighter and emptier as they ripen, with hulls and chaff scattered underneath. Freshly sown seed vanishing off the surface of a bed before it germinates. Bird traffic in and out of the plant picking up as the crop colors, and birds waiting on nearby wires and branches. Wasps arriving at the pecked and split fruit shortly afterward.

There is no treatment once a crop is being taken - only protection and timing, so the answer is to get netting on and to pick what is ready. Reflective tape, flash ribbon, spinners, and decoy predators do work, but only for a few days at a time: birds habituate fast, so move and rotate them and never rely on them as the main defense for a crop you care about. Cut and gather grain or seed heads a little early, at firm dough, and finish drying them under cover instead of leaving them standing for the flocks. Plant a little extra, or a decoy crop the birds prefer, and accept sharing anything that crops heavily. On a wild or foraged patch, fruit going to birds and small mammals is the point of the plant rather than a problem to solve.

Net, and net early. Bird netting draped over a frame or hoops so it stands off the fruit, with the edges closed at ground level, is the only thing that reliably works at harvest scale - and it has to go on before the crop starts to color, because once birds have found the food they are far harder to displace. Keep fruit trees small enough that netting them is actually feasible; that decision gets made years earlier, at planting. Bags of mesh, organza, or paper slipped over individual heads, clusters, or prize fruit protect a small crop without netting the whole plant. Then shorten the exposure: pick promptly and completely rather than leaving ripe fruit hanging as a lure, clear split and dropped fruit that draws birds and wasps alike, and where a crop can finish off the plant, harvest a little early and ripen or dry it under cover. Rake in or cover broadcast seed so it is not lying in plain view.

Birds find ripening fruit and seed before you do. Robins, waxwings, starlings, catbirds, jays, sparrows, finches, blackbirds, and doves all work a garden, and the pressure arrives in a narrow window - the last days before harvest, when sugar rises, color changes, and the crop softens or the grain hardens. A flock can strip a small planting in a day or two, and birds that only peck rather than take whole fruit still leave wounds that rot or draw wasps. Squirrels, chipmunks, and other wildlife usually turn up on the same crop at the same time. This is competition rather than disease: the birds are not harming the plant, and a big tree or a heavy-cropping bush often has enough for everyone - but on a small planting it can be the difference between a harvest and none.