The mud dauber wasp is a beneficial. It lays its eggs in its nest and includes an insect, usually a spider, in each egg cell to feed the dauber larvae when they hatch. So, most likely the wasp is looking for spiders; they may be small to see without a loop. If you suspect spiders, or spider mites, the best thing is just to give your tree a good wash with the hose.

My partner and I had some trouble a little while back when we first planted our tree and found out that our tree was nitrogen and magnesium deficient as the leaves were very light in colour and no fruit had been produced. We check the PH and fertilize as required with citrus feed but the pest issue seems to have gotten worse. The leave curl in this picture could be from frost? As we are in Winter here in Australia right now and the tree is in the middle of the backyard with little shelter - aside from the fence. This (see pic) is the first lemon we have seen for over a year and a half, since we got it from the nursery! So I am really hoping we can get a few more without the tree being eaten/destroyed... If anyone knows anything about this or has experienced the same sort of thing, your information would be greatly appreciated!

And this article addresses it in particular.... 2016 Florida Citrus Pest Management Guide: Ch. 20 Citrus Scab1 M.M. Dewdney 2 Citrus scab caused by the fungus Elsinoë fawcettii affects grapefruit, Temples, Murcotts, tangelos, and some other tangerine hybrids. There is no need to control citrus scab on processing fruit, except possibly Temples, where severe early infection reduces fruit size. Reduction or elimination of overhead irrigation on susceptible varieties during the active growth period of the fruit will decrease disease severity. Spores of this fungus are produced directly on scab pustules that occur on leaves and fruit. One to 2 hours of wetting are sufficient for spore production and only an additional 3–4 hours are needed for infection. Spores are spread to healthy tissues by water splash. If leaves from the previous season are heavily infected by citrus scab, 3 applications of fungicide may be needed to control the disease: one at about 1/4 expansion of the spring flush, a second at petal fall, and a third about three weeks later. With citrus scab, the timing of the spray applications is critical but if there is little carryover of disease from the previous season, the first spray can be omitted. Ferbam, Enable 2F, Abound, Gem, or Headline are good choices for the first application because they are all able to kill the fungus in old lesions and thus reduce inoculum as well as protecting foliage. Any of these products may then be used in the petal fall spray but do not use a strobilurin product (Abound, Gem, or Headline) twice in a row. Copper fungicides, Abound, Gem, or Headline are good choices for the third spray since they will protect fruit from early melanose as well as from scab, but copper products are less effective for scab and should not be selected where scab pressure is high. On Minneola tangelos, Murcotts, and certain other varieties, Alternaria brown spot and scab can occur in the same grove. In those cases, copper fungicides, Abound, Gem, or Headline may be preferred, since Ferbam and Enable 2F are less effective for Alternaria control. With average quality copper products, about 2 lb of metallic copper per acre are usually sufficient for scab control. The scab fungus may develop resistance to Abound, Gem, or Headline if these products are not rotated with alternate modes of action frequently. These products are all strobilurin fungicides and only one should be selected for scab control each season. Fruit usually becomes resistant to scab sometime in May, about 2 months after petal fall. DO NOT APPLY ABOUND,GEM, OR HEADLINE IN NURSERIES. Application of these fungicides in nurseries can result in selection of resistant strains which are then distributed on nursery stock to groves. Recommended Chemical Controls READ THE LABEL. See Table 1. Rates for pesticides are given as the maximum amount required to treat mature citrus trees unless otherwise noted. To treat smaller trees with commercial application equipment including handguns, mix the per acre rate for mature trees in 125 gallons of water. Calibrate and arrange nozzles to deliver thorough distribution and treat as many acres as this volume of spray allows. Tables Table 1. Recommended Chemical Controls for Citrus Scab. Pesticide FRAC MOA2 Mature Trees Rate/Acre1 copper fungicide M1 Use label rate. Enable 2F 3 8 fl oz. Do not apply more than 3 times per year; no more than 24 fl oz. (0.38 lb a.i.)/acre. Minimum retreatment interval is 21 days. Ferbam Granuflo M3 5-6 lb. Maximum 3 applications a year and do not apply more than 6 lb ai/acre in a single application. Abound3 11 12.0-15.5 fl oz. Do not apply more than 92.3 fl oz (1.5 lb ai)/acre/season for all uses. Gem 500 SC3 11 1.9-3.8 fl oz. Do not apply more than 15.2 fl oz/acre/season for all uses. Do not apply within 7 days of harvest. Headline SC3 11 9-12 fl oz. Do not apply more than 54 fl oz (0.88 lb ai)/acre/season for all uses. 1Lower rates can be used on smaller trees. Do not use less than the minimum label rate. 2Mode of action class for citrus pesticides from the Fungicide Resistance Action Committee (FRAC) 2015. Refer to ENY624, Pesticide Resistance and Resistance Management, in the 2016 Florida Citrus Pest Management Guide for more details. 3Do not use more than 4 applications of strobilurin fungicides/season. Do not make more than 2 sequential applications of strobilurin fungicides. Do not use in citrus propagation nurseries.

I am a bit nervous of the condition of my tree once it arrives. It shipped out 10/3/17 and will arrive 10/10/17, 7-8 days in a dark box sounds like that poor trees going to be in rough shape. What is the longest anyone's trees have been in transit for?